Remove Uptime.Last* parameters

This is technically a breaking change, but given how long ago this field was implemented as well as the fact that this is the default value if the type is not specified, I doubt anybody's explicitly setting it as inmemory

.dockerignore

@@ -1,3 +1,6 @@
 example
+Dockerfile
 .github
 .idea
+.git
+web/app

.gitattributes

@@ -0,0 +1 @@
+* text=lf

.github/FUNDING.yml

@@ -0,0 +1 @@
+github: [TwinProduction]

.github/assets/gatus-diagram.drawio

@@ -0,0 +1 @@
+<mxfile host="app.diagrams.net" modified="2021-07-30T04:27:17.723Z" agent="5.0 (Windows)" etag="hZKgW5ZLl0WUgYrCJXa4" version="14.9.2" type="device"><diagram id="1euQ5oT3BAcxlUCibzft" name="Page-1">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</diagram></mxfile>

.github/codecov.yml

@@ -0,0 +1,6 @@
+ignore:
+  - "watchdog/watchdog.go"
+
+coverage:
+  status:
+    patch: off

.github/workflows/build.yml

@@ -0,0 +1,33 @@
+name: build
+on:
+  pull_request:
+    paths-ignore:
+      - '*.md'
+  push:
+    branches:
+      - master
+    paths-ignore:
+      - '*.md'
+jobs:
+  build:
+    name: Build
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - name: Set up Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: 1.16
+      - name: Check out code into the Go module directory
+        uses: actions/checkout@v2
+      - name: Build binary to make sure it works
+        run: go build -mod vendor
+      - name: Test
+        # We're using "sudo" because one of the tests leverages ping, which requires super-user privileges.
+        # As for the 'env "PATH=$PATH" "GOROOT=$GOROOT"', we need it to use the same "go" executable that
+        # was configured by the "Set up Go 1.15" step (otherwise, it'd use sudo's "go" executable)
+        run: sudo env "PATH=$PATH" "GOROOT=$GOROOT" go test -mod vendor ./... -race -coverprofile=coverage.txt -covermode=atomic
+      - name: Codecov
+        uses: codecov/codecov-action@v1.5.2
+        with:
+          file: ./coverage.txt

.github/workflows/go.yml

@@ -1,34 +0,0 @@
-name: Go
-on: [push]
-jobs:
-  build-112:
-    name: Build with Go 1.12
-    runs-on: ubuntu-latest
-    steps:
-    - name: Set up Go 1.12
-      uses: actions/setup-go@v1
-      with:
-        go-version: 1.12
-      id: go
-    - name: Check out code into the Go module directory
-      uses: actions/checkout@v1
-    - name: Test
-      run: go test -mod vendor ./...
-    - name: Build
-      run: go build -mod vendor
-
-  build-113:
-    name: Build with Go 1.13
-    runs-on: ubuntu-latest
-    steps:
-      - name: Set up Go 1.13
-        uses: actions/setup-go@v1
-        with:
-          go-version: 1.13
-        id: go
-      - name: Check out code into the Go module directory
-        uses: actions/checkout@v1
-      - name: Test
-        run: go test -mod vendor ./...
-      - name: Build
-        run: go build -mod vendor

.github/workflows/publish-latest.yml

@@ -0,0 +1,34 @@
+name: publish-latest
+on:
+  workflow_run:
+    workflows: ["build"]
+    branches: [master]
+    types: [completed]
+jobs:
+  publish-latest:
+    name: Publish latest
+    runs-on: ubuntu-latest
+    if: ${{ github.event.workflow_run.conclusion == 'success' }}
+    timeout-minutes: 30
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v2
+      - name: Get image repository
+        run: echo IMAGE_REPOSITORY=$(echo ${{ github.repository }} | tr '[:upper:]' '[:lower:]') >> $GITHUB_ENV
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+      - name: Login to Docker Registry
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+      - name: Build and push docker image
+        uses: docker/build-push-action@v2
+        with:
+          platforms: linux/amd64
+          pull: true
+          push: true
+          tags: |
+            ${{ env.IMAGE_REPOSITORY }}:latest

.github/workflows/publish-release.yml

@@ -0,0 +1,33 @@
+name: publish-release
+on:
+  release:
+    types: [published]
+jobs:
+  publish-release:
+    name: Publish release
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v2
+      - name: Get image repository
+        run: echo IMAGE_REPOSITORY=$(echo ${{ github.repository }} | tr '[:upper:]' '[:lower:]') >> $GITHUB_ENV
+      - name: Get the release
+        run: echo RELEASE=${GITHUB_REF/refs\/tags\//} >> $GITHUB_ENV
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+      - name: Login to Docker Registry
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+      - name: Build and push docker image
+        uses: docker/build-push-action@v2
+        with:
+          platforms: linux/amd64,linux/arm/v7,linux/arm64
+          pull: true
+          push: true
+          tags: |
+            ${{ env.IMAGE_REPOSITORY }}:${{ env.RELEASE }}

.gitignore

@@ -1,4 +1,8 @@
-bin
 .idea
-test.db
-daily.db
+.vscode
+gatus
+db.db
+config/config.yml
+db.db-shm
+db.db-wal
+memory.db

Dockerfile

@@ -1,16 +1,20 @@
 # Build the go application into a binary
 FROM golang:alpine as builder
-WORKDIR /app
-ADD . ./
-RUN CGO_ENABLED=0 GOOS=linux go build -mod vendor -a -installsuffix cgo -o gatus .
 RUN apk --update add ca-certificates
+WORKDIR /app
+COPY . ./
+RUN CGO_ENABLED=0 GOOS=linux go build -mod vendor -a -installsuffix cgo -o gatus .
+
+# Run Tests inside docker image if you don't have a configured go environment
+#RUN apk update && apk add --virtual build-dependencies build-base gcc
+#RUN go test ./... -mod vendor
 
 # Run the binary on an empty container
 FROM scratch
 COPY --from=builder /app/gatus .
 COPY --from=builder /app/config.yaml ./config/config.yaml
-COPY --from=builder /app/static static/
+COPY --from=builder /app/web/static ./web/static
 COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
 ENV PORT=8080
 EXPOSE ${PORT}
-ENTRYPOINT ["/gatus"]
+ENTRYPOINT ["/gatus"]

LICENSE.md

@@ -1,201 +1,9 @@
-                                 Apache License
-                           Version 2.0, January 2004
-                        http://www.apache.org/licenses/
+MIT License
 
-   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+Copyright (c) 2021 TwinProduction
 
-   1. Definitions.
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 
-      "License" shall mean the terms and conditions for use, reproduction,
-      and distribution as defined by Sections 1 through 9 of this document.
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 
-      "Licensor" shall mean the copyright owner or entity authorized by
-      the copyright owner that is granting the License.
-
-      "Legal Entity" shall mean the union of the acting entity and all
-      other entities that control, are controlled by, or are under common
-      control with that entity. For the purposes of this definition,
-      "control" means (i) the power, direct or indirect, to cause the
-      direction or management of such entity, whether by contract or
-      otherwise, or (ii) ownership of fifty percent (50%) or more of the
-      outstanding shares, or (iii) beneficial ownership of such entity.
-
-      "You" (or "Your") shall mean an individual or Legal Entity
-      exercising permissions granted by this License.
-
-      "Source" form shall mean the preferred form for making modifications,
-      including but not limited to software source code, documentation
-      source, and configuration files.
-
-      "Object" form shall mean any form resulting from mechanical
-      transformation or translation of a Source form, including but
-      not limited to compiled object code, generated documentation,
-      and conversions to other media types.
-
-      "Work" shall mean the work of authorship, whether in Source or
-      Object form, made available under the License, as indicated by a
-      copyright notice that is included in or attached to the work
-      (an example is provided in the Appendix below).
-
-      "Derivative Works" shall mean any work, whether in Source or Object
-      form, that is based on (or derived from) the Work and for which the
-      editorial revisions, annotations, elaborations, or other modifications
-      represent, as a whole, an original work of authorship. For the purposes
-      of this License, Derivative Works shall not include works that remain
-      separable from, or merely link (or bind by name) to the interfaces of,
-      the Work and Derivative Works thereof.
-
-      "Contribution" shall mean any work of authorship, including
-      the original version of the Work and any modifications or additions
-      to that Work or Derivative Works thereof, that is intentionally
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-      means any form of electronic, verbal, or written communication sent
-      to the Licensor or its representatives, including but not limited to
-      communication on electronic mailing lists, source code control systems,
-      and issue tracking systems that are managed by, or on behalf of, the
-      Licensor for the purpose of discussing and improving the Work, but
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-      designated in writing by the copyright owner as "Not a Contribution."
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-      "Contributor" shall mean Licensor and any individual or Legal Entity
-      on behalf of whom a Contribution has been received by Licensor and
-      subsequently incorporated within the Work.
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-          of the following places: within a NOTICE text file distributed
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-          of the NOTICE file are for informational purposes only and
-          do not modify the License. You may add Your own attribution
-          notices within Derivative Works that You distribute, alongside
-          or as an addendum to the NOTICE text from the Work, provided
-          that such additional attribution notices cannot be construed
-          as modifying the License.
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-      You may add Your own copyright statement to Your modifications and
-      may provide additional or different license terms and conditions
-      for use, reproduction, or distribution of Your modifications, or
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-      reproduction, and distribution of the Work otherwise complies with
-      the conditions stated in this License.
-
-   5. Submission of Contributions. Unless You explicitly state otherwise,
-      any Contribution intentionally submitted for inclusion in the Work
-      by You to the Licensor shall be under the terms and conditions of
-      this License, without any additional terms or conditions.
-      Notwithstanding the above, nothing herein shall supersede or modify
-      the terms of any separate license agreement you may have executed
-      with Licensor regarding such Contributions.
-
-   6. Trademarks. This License does not grant permission to use the trade
-      names, trademarks, service marks, or product names of the Licensor,
-      except as required for reasonable and customary use in describing the
-      origin of the Work and reproducing the content of the NOTICE file.
-
-   7. Disclaimer of Warranty. Unless required by applicable law or
-      agreed to in writing, Licensor provides the Work (and each
-      Contributor provides its Contributions) on an "AS IS" BASIS,
-      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
-      implied, including, without limitation, any warranties or conditions
-      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
-      PARTICULAR PURPOSE. You are solely responsible for determining the
-      appropriateness of using or redistributing the Work and assume any
-      risks associated with Your exercise of permissions under this License.
-
-   8. Limitation of Liability. In no event and under no legal theory,
-      whether in tort (including negligence), contract, or otherwise,
-      unless required by applicable law (such as deliberate and grossly
-      negligent acts) or agreed to in writing, shall any Contributor be
-      liable to You for damages, including any direct, indirect, special,
-      incidental, or consequential damages of any character arising as a
-      result of this License or out of the use or inability to use the
-      Work (including but not limited to damages for loss of goodwill,
-      work stoppage, computer failure or malfunction, or any and all
-      other commercial damages or losses), even if such Contributor
-      has been advised of the possibility of such damages.
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-   9. Accepting Warranty or Additional Liability. While redistributing
-      the Work or Derivative Works thereof, You may choose to offer,
-      and charge a fee for, acceptance of support, warranty, indemnity,
-      or other liability obligations and/or rights consistent with this
-      License. However, in accepting such obligations, You may act only
-      on Your own behalf and on Your sole responsibility, not on behalf
-      of any other Contributor, and only if You agree to indemnify,
-      defend, and hold each Contributor harmless for any liability
-      incurred by, or claims asserted against, such Contributor by reason
-      of your accepting any such warranty or additional liability.
-
-   END OF TERMS AND CONDITIONS
-
-   APPENDIX: How to apply the Apache License to your work.
-
-      To apply the Apache License to your work, attach the following
-      boilerplate notice, with the fields enclosed by brackets "[]"
-      replaced with your own identifying information. (Don't include
-      the brackets!)  The text should be enclosed in the appropriate
-      comment syntax for the file format. We also recommend that a
-      file or class name and description of purpose be included on the
-      same "printed page" as the copyright notice for easier
-      identification within third-party archives.
-
-   Copyright [yyyy] [name of copyright owner]
-
-   Licensed under the Apache License, Version 2.0 (the "License");
-   you may not use this file except in compliance with the License.
-   You may obtain a copy of the License at
-
-       http://www.apache.org/licenses/LICENSE-2.0
-
-   Unless required by applicable law or agreed to in writing, software
-   distributed under the License is distributed on an "AS IS" BASIS,
-   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-   See the License for the specific language governing permissions and
-   limitations under the License.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Makefile

@@ -0,0 +1,14 @@
+docker-build:
+	docker build -t twinproduction/gatus:latest .
+
+docker-build-and-run:
+	docker build -t twinproduction/gatus:latest . && docker run -p 8080:8080 --name gatus twinproduction/gatus:latest
+
+build-frontend:
+	npm --prefix web/app run build
+
+run-frontend:
+	npm --prefix web/app run serve
+
+test:
+	go test ./alerting/... ./client/... ./config/... ./controller/... ./core/... ./jsonpath/... ./pattern/... ./security/... ./storage/... ./util/... ./watchdog/... -cover

alerting/alert/alert.go

@@ -0,0 +1,69 @@
+package alert
+
+// Alert is the service's alert configuration
+type Alert struct {
+	// Type of alert (required)
+	Type Type `yaml:"type"`
+
+	// Enabled defines whether or not the alert is enabled
+	//
+	// This is a pointer, because it is populated by YAML and we need to know whether it was explicitly set to a value
+	// or not for provider.ParseWithDefaultAlert to work.
+	Enabled *bool `yaml:"enabled"`
+
+	// FailureThreshold is the number of failures in a row needed before triggering the alert
+	FailureThreshold int `yaml:"failure-threshold"`
+
+	// Description of the alert. Will be included in the alert sent.
+	//
+	// This is a pointer, because it is populated by YAML and we need to know whether it was explicitly set to a value
+	// or not for provider.ParseWithDefaultAlert to work.
+	Description *string `yaml:"description"`
+
+	// SendOnResolved defines whether to send a second notification when the issue has been resolved
+	//
+	// This is a pointer, because it is populated by YAML and we need to know whether it was explicitly set to a value
+	// or not for provider.ParseWithDefaultAlert to work. Use Alert.IsSendingOnResolved() for a non-pointer
+	SendOnResolved *bool `yaml:"send-on-resolved"`
+
+	// SuccessThreshold defines how many successful executions must happen in a row before an ongoing incident is marked as resolved
+	SuccessThreshold int `yaml:"success-threshold"`
+
+	// ResolveKey is an optional field that is used by some providers (i.e. PagerDuty's dedup_key) to resolve
+	// ongoing/triggered incidents
+	ResolveKey string
+
+	// Triggered is used to determine whether an alert has been triggered. When an alert is resolved, this value
+	// should be set back to false. It is used to prevent the same alert from going out twice.
+	//
+	// This value should only be modified if the provider.AlertProvider's Send function does not return an error for an
+	// alert that hasn't been triggered yet. This doubles as a lazy retry. The reason why this behavior isn't also
+	// applied for alerts that are already triggered and has become "healthy" again is to prevent a case where, for
+	// some reason, the alert provider always returns errors when trying to send the resolved notification
+	// (SendOnResolved).
+	Triggered bool
+}
+
+// GetDescription retrieves the description of the alert
+func (alert Alert) GetDescription() string {
+	if alert.Description == nil {
+		return ""
+	}
+	return *alert.Description
+}
+
+// IsEnabled returns whether an alert is enabled or not
+func (alert Alert) IsEnabled() bool {
+	if alert.Enabled == nil {
+		return false
+	}
+	return *alert.Enabled
+}
+
+// IsSendingOnResolved returns whether an alert is sending on resolve or not
+func (alert Alert) IsSendingOnResolved() bool {
+	if alert.SendOnResolved == nil {
+		return false
+	}
+	return *alert.SendOnResolved
+}

alerting/alert/alert_test.go

@@ -0,0 +1,36 @@
+package alert
+
+import "testing"
+
+func TestAlert_IsEnabled(t *testing.T) {
+	if (Alert{Enabled: nil}).IsEnabled() {
+		t.Error("alert.IsEnabled() should've returned false, because Enabled was set to nil")
+	}
+	if value := false; (Alert{Enabled: &value}).IsEnabled() {
+		t.Error("alert.IsEnabled() should've returned false, because Enabled was set to false")
+	}
+	if value := true; !(Alert{Enabled: &value}).IsEnabled() {
+		t.Error("alert.IsEnabled() should've returned true, because Enabled was set to true")
+	}
+}
+
+func TestAlert_GetDescription(t *testing.T) {
+	if (Alert{Description: nil}).GetDescription() != "" {
+		t.Error("alert.GetDescription() should've returned an empty string, because Description was set to nil")
+	}
+	if value := "description"; (Alert{Description: &value}).GetDescription() != value {
+		t.Error("alert.GetDescription() should've returned false, because Description was set to 'description'")
+	}
+}
+
+func TestAlert_IsSendingOnResolved(t *testing.T) {
+	if (Alert{SendOnResolved: nil}).IsSendingOnResolved() {
+		t.Error("alert.IsSendingOnResolved() should've returned false, because SendOnResolved was set to nil")
+	}
+	if value := false; (Alert{SendOnResolved: &value}).IsSendingOnResolved() {
+		t.Error("alert.IsSendingOnResolved() should've returned false, because SendOnResolved was set to false")
+	}
+	if value := true; !(Alert{SendOnResolved: &value}).IsSendingOnResolved() {
+		t.Error("alert.IsSendingOnResolved() should've returned true, because SendOnResolved was set to true")
+	}
+}

alerting/alert/type.go

@@ -0,0 +1,34 @@
+package alert
+
+// Type is the type of the alert.
+// The value will generally be the name of the alert provider
+type Type string
+
+const (
+	// TypeCustom is the Type for the custom alerting provider
+	TypeCustom Type = "custom"
+
+	// TypeDiscord is the Type for the discord alerting provider
+	TypeDiscord Type = "discord"
+
+	// TypeMattermost is the Type for the mattermost alerting provider
+	TypeMattermost Type = "mattermost"
+
+	// TypeMessagebird is the Type for the messagebird alerting provider
+	TypeMessagebird Type = "messagebird"
+
+	// TypePagerDuty is the Type for the pagerduty alerting provider
+	TypePagerDuty Type = "pagerduty"
+
+	// TypeSlack is the Type for the slack alerting provider
+	TypeSlack Type = "slack"
+
+	// TypeTeams is the Type for the teams alerting provider
+	TypeTeams Type = "teams"
+
+	// TypeTelegram is the Type for the telegram alerting provider
+	TypeTelegram Type = "telegram"
+
+	// TypeTwilio is the Type for the twilio alerting provider
+	TypeTwilio Type = "twilio"
+)

alerting/config.go

@@ -0,0 +1,106 @@
+package alerting
+
+import (
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/alerting/provider"
+	"github.com/TwinProduction/gatus/alerting/provider/custom"
+	"github.com/TwinProduction/gatus/alerting/provider/discord"
+	"github.com/TwinProduction/gatus/alerting/provider/mattermost"
+	"github.com/TwinProduction/gatus/alerting/provider/messagebird"
+	"github.com/TwinProduction/gatus/alerting/provider/pagerduty"
+	"github.com/TwinProduction/gatus/alerting/provider/slack"
+	"github.com/TwinProduction/gatus/alerting/provider/teams"
+	"github.com/TwinProduction/gatus/alerting/provider/telegram"
+	"github.com/TwinProduction/gatus/alerting/provider/twilio"
+)
+
+// Config is the configuration for alerting providers
+type Config struct {
+	// Custom is the configuration for the custom alerting provider
+	Custom *custom.AlertProvider `yaml:"custom"`
+
+	// Discord is the configuration for the discord alerting provider
+	Discord *discord.AlertProvider `yaml:"discord"`
+
+	// Mattermost is the configuration for the mattermost alerting provider
+	Mattermost *mattermost.AlertProvider `yaml:"mattermost"`
+
+	// Messagebird is the configuration for the messagebird alerting provider
+	Messagebird *messagebird.AlertProvider `yaml:"messagebird"`
+
+	// PagerDuty is the configuration for the pagerduty alerting provider
+	PagerDuty *pagerduty.AlertProvider `yaml:"pagerduty"`
+
+	// Slack is the configuration for the slack alerting provider
+	Slack *slack.AlertProvider `yaml:"slack"`
+
+	// Teams is the configuration for the teams alerting provider
+	Teams *teams.AlertProvider `yaml:"teams"`
+
+	// Telegram is the configuration for the telegram alerting provider
+	Telegram *telegram.AlertProvider `yaml:"telegram"`
+
+	// Twilio is the configuration for the twilio alerting provider
+	Twilio *twilio.AlertProvider `yaml:"twilio"`
+}
+
+// GetAlertingProviderByAlertType returns an provider.AlertProvider by its corresponding alert.Type
+func (config Config) GetAlertingProviderByAlertType(alertType alert.Type) provider.AlertProvider {
+	switch alertType {
+	case alert.TypeCustom:
+		if config.Custom == nil {
+			// Since we're returning an interface, we need to explicitly return nil, even if the provider itself is nil
+			return nil
+		}
+		return config.Custom
+	case alert.TypeDiscord:
+		if config.Discord == nil {
+			// Since we're returning an interface, we need to explicitly return nil, even if the provider itself is nil
+			return nil
+		}
+		return config.Discord
+	case alert.TypeMattermost:
+		if config.Mattermost == nil {
+			// Since we're returning an interface, we need to explicitly return nil, even if the provider itself is nil
+			return nil
+		}
+		return config.Mattermost
+	case alert.TypeMessagebird:
+		if config.Messagebird == nil {
+			// Since we're returning an interface, we need to explicitly return nil, even if the provider itself is nil
+			return nil
+		}
+		return config.Messagebird
+	case alert.TypePagerDuty:
+		if config.PagerDuty == nil {
+			// Since we're returning an interface, we need to explicitly return nil, even if the provider itself is nil
+			return nil
+		}
+		return config.PagerDuty
+	case alert.TypeSlack:
+		if config.Slack == nil {
+			// Since we're returning an interface, we need to explicitly return nil, even if the provider itself is nil
+			return nil
+		}
+		return config.Slack
+	case alert.TypeTeams:
+		if config.Teams == nil {
+			// Since we're returning an interface, we need to explicitly return nil, even if the provider itself is nil
+			return nil
+		}
+		return config.Teams
+	case alert.TypeTelegram:
+		if config.Telegram == nil {
+			// Since we're returning an interface, we need to explicitly return nil, even if the provider itself is nil
+			return nil
+		}
+		return config.Telegram
+	case alert.TypeTwilio:
+		if config.Twilio == nil {
+			// Since we're returning an interface, we need to explicitly return nil, even if the provider itself is nil
+			return nil
+		}
+		return config.Twilio
+	}
+	return nil
+}

alerting/provider/custom/custom.go

@@ -0,0 +1,135 @@
+package custom
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+	"strings"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/client"
+	"github.com/TwinProduction/gatus/core"
+)
+
+// AlertProvider is the configuration necessary for sending an alert using a custom HTTP request
+// Technically, all alert providers should be reachable using the custom alert provider
+type AlertProvider struct {
+	URL          string                       `yaml:"url"`
+	Method       string                       `yaml:"method,omitempty"`
+	Insecure     bool                         `yaml:"insecure,omitempty"` // deprecated
+	Body         string                       `yaml:"body,omitempty"`
+	Headers      map[string]string            `yaml:"headers,omitempty"`
+	Placeholders map[string]map[string]string `yaml:"placeholders,omitempty"`
+
+	// ClientConfig is the configuration of the client used to communicate with the provider's target
+	ClientConfig *client.Config `yaml:"client"`
+
+	// DefaultAlert is the default alert configuration to use for services with an alert of the appropriate type
+	DefaultAlert *alert.Alert `yaml:"default-alert"`
+}
+
+// IsValid returns whether the provider's configuration is valid
+func (provider *AlertProvider) IsValid() bool {
+	if provider.ClientConfig == nil {
+		provider.ClientConfig = client.GetDefaultConfig()
+		// XXX: remove the next 4 lines in v3.0.0
+		if provider.Insecure {
+			log.Println("WARNING: alerting.*.insecure has been deprecated and will be removed in v3.0.0 in favor of alerting.*.client.insecure")
+			provider.ClientConfig.Insecure = true
+		}
+	}
+	return len(provider.URL) > 0 && provider.ClientConfig != nil
+}
+
+// ToCustomAlertProvider converts the provider into a custom.AlertProvider
+func (provider *AlertProvider) ToCustomAlertProvider(service *core.Service, alert *alert.Alert, result *core.Result, resolved bool) *AlertProvider {
+	return provider
+}
+
+// GetAlertStatePlaceholderValue returns the Placeholder value for ALERT_TRIGGERED_OR_RESOLVED if configured
+func (provider *AlertProvider) GetAlertStatePlaceholderValue(resolved bool) string {
+	status := "TRIGGERED"
+	if resolved {
+		status = "RESOLVED"
+	}
+	if _, ok := provider.Placeholders["ALERT_TRIGGERED_OR_RESOLVED"]; ok {
+		if val, ok := provider.Placeholders["ALERT_TRIGGERED_OR_RESOLVED"][status]; ok {
+			return val
+		}
+	}
+	return status
+}
+
+func (provider *AlertProvider) buildHTTPRequest(serviceName, alertDescription string, resolved bool) *http.Request {
+	body := provider.Body
+	providerURL := provider.URL
+	method := provider.Method
+
+	if strings.Contains(body, "[ALERT_DESCRIPTION]") {
+		body = strings.ReplaceAll(body, "[ALERT_DESCRIPTION]", alertDescription)
+	}
+	if strings.Contains(body, "[SERVICE_NAME]") {
+		body = strings.ReplaceAll(body, "[SERVICE_NAME]", serviceName)
+	}
+	if strings.Contains(body, "[ALERT_TRIGGERED_OR_RESOLVED]") {
+		if resolved {
+			body = strings.ReplaceAll(body, "[ALERT_TRIGGERED_OR_RESOLVED]", provider.GetAlertStatePlaceholderValue(true))
+		} else {
+			body = strings.ReplaceAll(body, "[ALERT_TRIGGERED_OR_RESOLVED]", provider.GetAlertStatePlaceholderValue(false))
+		}
+	}
+	if strings.Contains(providerURL, "[ALERT_DESCRIPTION]") {
+		providerURL = strings.ReplaceAll(providerURL, "[ALERT_DESCRIPTION]", alertDescription)
+	}
+	if strings.Contains(providerURL, "[SERVICE_NAME]") {
+		providerURL = strings.ReplaceAll(providerURL, "[SERVICE_NAME]", serviceName)
+	}
+	if strings.Contains(providerURL, "[ALERT_TRIGGERED_OR_RESOLVED]") {
+		if resolved {
+			providerURL = strings.ReplaceAll(providerURL, "[ALERT_TRIGGERED_OR_RESOLVED]", provider.GetAlertStatePlaceholderValue(true))
+		} else {
+			providerURL = strings.ReplaceAll(providerURL, "[ALERT_TRIGGERED_OR_RESOLVED]", provider.GetAlertStatePlaceholderValue(false))
+		}
+	}
+	if len(method) == 0 {
+		method = http.MethodGet
+	}
+	bodyBuffer := bytes.NewBuffer([]byte(body))
+	request, _ := http.NewRequest(method, providerURL, bodyBuffer)
+	for k, v := range provider.Headers {
+		request.Header.Set(k, v)
+	}
+	return request
+}
+
+// Send a request to the alert provider and return the body
+func (provider *AlertProvider) Send(serviceName, alertDescription string, resolved bool) ([]byte, error) {
+	if os.Getenv("MOCK_ALERT_PROVIDER") == "true" {
+		if os.Getenv("MOCK_ALERT_PROVIDER_ERROR") == "true" {
+			return nil, errors.New("error")
+		}
+		return []byte("{}"), nil
+	}
+	request := provider.buildHTTPRequest(serviceName, alertDescription, resolved)
+	response, err := client.GetHTTPClient(provider.ClientConfig).Do(request)
+	if err != nil {
+		return nil, err
+	}
+	if response.StatusCode > 399 {
+		body, err := ioutil.ReadAll(response.Body)
+		if err != nil {
+			return nil, fmt.Errorf("call to provider alert returned status code %d", response.StatusCode)
+		}
+		return nil, fmt.Errorf("call to provider alert returned status code %d: %s", response.StatusCode, string(body))
+	}
+	return ioutil.ReadAll(response.Body)
+}
+
+// GetDefaultAlert returns the provider's default alert configuration
+func (provider AlertProvider) GetDefaultAlert() *alert.Alert {
+	return provider.DefaultAlert
+}

alerting/provider/custom/custom_test.go

@@ -0,0 +1,111 @@
+package custom
+
+import (
+	"io/ioutil"
+	"testing"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/core"
+)
+
+func TestAlertProvider_IsValid(t *testing.T) {
+	invalidProvider := AlertProvider{URL: ""}
+	if invalidProvider.IsValid() {
+		t.Error("provider shouldn't have been valid")
+	}
+	validProvider := AlertProvider{URL: "http://example.com"}
+	if !validProvider.IsValid() {
+		t.Error("provider should've been valid")
+	}
+}
+
+func TestAlertProvider_buildHTTPRequestWhenResolved(t *testing.T) {
+	const (
+		ExpectedURL  = "http://example.com/service-name?event=RESOLVED&description=alert-description"
+		ExpectedBody = "service-name,alert-description,RESOLVED"
+	)
+	customAlertProvider := &AlertProvider{
+		URL:     "http://example.com/[SERVICE_NAME]?event=[ALERT_TRIGGERED_OR_RESOLVED]&description=[ALERT_DESCRIPTION]",
+		Body:    "[SERVICE_NAME],[ALERT_DESCRIPTION],[ALERT_TRIGGERED_OR_RESOLVED]",
+		Headers: nil,
+	}
+	request := customAlertProvider.buildHTTPRequest("service-name", "alert-description", true)
+	if request.URL.String() != ExpectedURL {
+		t.Error("expected URL to be", ExpectedURL, "was", request.URL.String())
+	}
+	body, _ := ioutil.ReadAll(request.Body)
+	if string(body) != ExpectedBody {
+		t.Error("expected body to be", ExpectedBody, "was", string(body))
+	}
+}
+
+func TestAlertProvider_buildHTTPRequestWhenTriggered(t *testing.T) {
+	const (
+		ExpectedURL  = "http://example.com/service-name?event=TRIGGERED&description=alert-description"
+		ExpectedBody = "service-name,alert-description,TRIGGERED"
+	)
+	customAlertProvider := &AlertProvider{
+		URL:     "http://example.com/[SERVICE_NAME]?event=[ALERT_TRIGGERED_OR_RESOLVED]&description=[ALERT_DESCRIPTION]",
+		Body:    "[SERVICE_NAME],[ALERT_DESCRIPTION],[ALERT_TRIGGERED_OR_RESOLVED]",
+		Headers: map[string]string{"Authorization": "Basic hunter2"},
+	}
+	request := customAlertProvider.buildHTTPRequest("service-name", "alert-description", false)
+	if request.URL.String() != ExpectedURL {
+		t.Error("expected URL to be", ExpectedURL, "was", request.URL.String())
+	}
+	body, _ := ioutil.ReadAll(request.Body)
+	if string(body) != ExpectedBody {
+		t.Error("expected body to be", ExpectedBody, "was", string(body))
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProvider(t *testing.T) {
+	provider := AlertProvider{URL: "http://example.com"}
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{}, &alert.Alert{}, &core.Result{}, true)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if customAlertProvider.URL != "http://example.com" {
+		t.Error("expected URL to be http://example.com, got", customAlertProvider.URL)
+	}
+}
+
+func TestAlertProvider_buildHTTPRequestWithCustomPlaceholder(t *testing.T) {
+	const (
+		ExpectedURL  = "http://example.com/service-name?event=test&description=alert-description"
+		ExpectedBody = "service-name,alert-description,test"
+	)
+	customAlertProvider := &AlertProvider{
+		URL:     "http://example.com/[SERVICE_NAME]?event=[ALERT_TRIGGERED_OR_RESOLVED]&description=[ALERT_DESCRIPTION]",
+		Body:    "[SERVICE_NAME],[ALERT_DESCRIPTION],[ALERT_TRIGGERED_OR_RESOLVED]",
+		Headers: nil,
+		Placeholders: map[string]map[string]string{
+			"ALERT_TRIGGERED_OR_RESOLVED": {
+				"RESOLVED": "test",
+			},
+		},
+	}
+	request := customAlertProvider.buildHTTPRequest("service-name", "alert-description", true)
+	if request.URL.String() != ExpectedURL {
+		t.Error("expected URL to be", ExpectedURL, "was", request.URL.String())
+	}
+	body, _ := ioutil.ReadAll(request.Body)
+	if string(body) != ExpectedBody {
+		t.Error("expected body to be", ExpectedBody, "was", string(body))
+	}
+}
+
+func TestAlertProvider_GetAlertStatePlaceholderValueDefaults(t *testing.T) {
+	customAlertProvider := &AlertProvider{
+		URL:          "http://example.com/[SERVICE_NAME]?event=[ALERT_TRIGGERED_OR_RESOLVED]&description=[ALERT_DESCRIPTION]",
+		Body:         "[SERVICE_NAME],[ALERT_DESCRIPTION],[ALERT_TRIGGERED_OR_RESOLVED]",
+		Headers:      nil,
+		Placeholders: nil,
+	}
+	if customAlertProvider.GetAlertStatePlaceholderValue(true) != "RESOLVED" {
+		t.Error("expected RESOLVED, got", customAlertProvider.GetAlertStatePlaceholderValue(true))
+	}
+	if customAlertProvider.GetAlertStatePlaceholderValue(false) != "TRIGGERED" {
+		t.Error("expected TRIGGERED, got", customAlertProvider.GetAlertStatePlaceholderValue(false))
+	}
+}

alerting/provider/discord/discord.go

@@ -0,0 +1,76 @@
+package discord
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/alerting/provider/custom"
+	"github.com/TwinProduction/gatus/core"
+)
+
+// AlertProvider is the configuration necessary for sending an alert using Discord
+type AlertProvider struct {
+	WebhookURL string `yaml:"webhook-url"`
+
+	// DefaultAlert is the default alert configuration to use for services with an alert of the appropriate type
+	DefaultAlert *alert.Alert `yaml:"default-alert"`
+}
+
+// IsValid returns whether the provider's configuration is valid
+func (provider *AlertProvider) IsValid() bool {
+	return len(provider.WebhookURL) > 0
+}
+
+// ToCustomAlertProvider converts the provider into a custom.AlertProvider
+func (provider *AlertProvider) ToCustomAlertProvider(service *core.Service, alert *alert.Alert, result *core.Result, resolved bool) *custom.AlertProvider {
+	var message, results string
+	var colorCode int
+	if resolved {
+		message = fmt.Sprintf("An alert for **%s** has been resolved after passing successfully %d time(s) in a row", service.Name, alert.SuccessThreshold)
+		colorCode = 3066993
+	} else {
+		message = fmt.Sprintf("An alert for **%s** has been triggered due to having failed %d time(s) in a row", service.Name, alert.FailureThreshold)
+		colorCode = 15158332
+	}
+	for _, conditionResult := range result.ConditionResults {
+		var prefix string
+		if conditionResult.Success {
+			prefix = ":white_check_mark:"
+		} else {
+			prefix = ":x:"
+		}
+		results += fmt.Sprintf("%s - `%s`\\n", prefix, conditionResult.Condition)
+	}
+	var description string
+	if alertDescription := alert.GetDescription(); len(alertDescription) > 0 {
+		description = ":\\n> " + alertDescription
+	}
+	return &custom.AlertProvider{
+		URL:    provider.WebhookURL,
+		Method: http.MethodPost,
+		Body: fmt.Sprintf(`{
+  "content": "",
+  "embeds": [
+    {
+      "title": ":helmet_with_white_cross: Gatus",
+      "description": "%s%s",
+      "color": %d,
+      "fields": [
+        {
+          "name": "Condition results",
+          "value": "%s",
+          "inline": false
+        }
+      ]
+    }
+  ]
+}`, message, description, colorCode, results),
+		Headers: map[string]string{"Content-Type": "application/json"},
+	}
+}
+
+// GetDefaultAlert returns the provider's default alert configuration
+func (provider AlertProvider) GetDefaultAlert() *alert.Alert {
+	return provider.DefaultAlert
+}

alerting/provider/discord/discord_test.go

@@ -0,0 +1,70 @@
+package discord
+
+import (
+	"encoding/json"
+	"net/http"
+	"strings"
+	"testing"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/core"
+)
+
+func TestAlertProvider_IsValid(t *testing.T) {
+	invalidProvider := AlertProvider{WebhookURL: ""}
+	if invalidProvider.IsValid() {
+		t.Error("provider shouldn't have been valid")
+	}
+	validProvider := AlertProvider{WebhookURL: "http://example.com"}
+	if !validProvider.IsValid() {
+		t.Error("provider should've been valid")
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProviderWithResolvedAlert(t *testing.T) {
+	provider := AlertProvider{WebhookURL: "http://example.com"}
+	alertDescription := "test"
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{Name: "svc"}, &alert.Alert{Description: &alertDescription}, &core.Result{ConditionResults: []*core.ConditionResult{{Condition: "SUCCESSFUL_CONDITION", Success: true}}}, true)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if !strings.Contains(customAlertProvider.Body, "resolved") {
+		t.Error("customAlertProvider.Body should've contained the substring resolved")
+	}
+	if customAlertProvider.URL != "http://example.com" {
+		t.Errorf("expected URL to be %s, got %s", "http://example.com", customAlertProvider.URL)
+	}
+	if customAlertProvider.Method != http.MethodPost {
+		t.Errorf("expected method to be %s, got %s", http.MethodPost, customAlertProvider.Method)
+	}
+	body := make(map[string]interface{})
+	err := json.Unmarshal([]byte(customAlertProvider.Body), &body)
+	if err != nil {
+		t.Error("expected body to be valid JSON, got error:", err.Error())
+	}
+	if expected := "An alert for **svc** has been resolved after passing successfully 0 time(s) in a row:\n> test"; expected != body["embeds"].([]interface{})[0].(map[string]interface{})["description"] {
+		t.Errorf("expected $.embeds[0].description to be %s, got %s", expected, body["embeds"].([]interface{})[0].(map[string]interface{})["description"])
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProviderWithTriggeredAlert(t *testing.T) {
+	provider := AlertProvider{WebhookURL: "http://example.com"}
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{}, &alert.Alert{}, &core.Result{ConditionResults: []*core.ConditionResult{{Condition: "UNSUCCESSFUL_CONDITION", Success: false}}}, false)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if !strings.Contains(customAlertProvider.Body, "triggered") {
+		t.Error("customAlertProvider.Body should've contained the substring triggered")
+	}
+	if customAlertProvider.URL != "http://example.com" {
+		t.Errorf("expected URL to be %s, got %s", "http://example.com", customAlertProvider.URL)
+	}
+	if customAlertProvider.Method != http.MethodPost {
+		t.Errorf("expected method to be %s, got %s", http.MethodPost, customAlertProvider.Method)
+	}
+	body := make(map[string]interface{})
+	err := json.Unmarshal([]byte(customAlertProvider.Body), &body)
+	if err != nil {
+		t.Error("expected body to be valid JSON, got error:", err.Error())
+	}
+}

alerting/provider/mattermost/mattermost.go

@@ -0,0 +1,101 @@
+package mattermost
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/alerting/provider/custom"
+	"github.com/TwinProduction/gatus/client"
+	"github.com/TwinProduction/gatus/core"
+)
+
+// AlertProvider is the configuration necessary for sending an alert using Mattermost
+type AlertProvider struct {
+	WebhookURL string `yaml:"webhook-url"`
+	Insecure   bool   `yaml:"insecure,omitempty"` // deprecated
+
+	// ClientConfig is the configuration of the client used to communicate with the provider's target
+	ClientConfig *client.Config `yaml:"client"`
+
+	// DefaultAlert is the default alert configuration to use for services with an alert of the appropriate type
+	DefaultAlert *alert.Alert `yaml:"default-alert"`
+}
+
+// IsValid returns whether the provider's configuration is valid
+func (provider *AlertProvider) IsValid() bool {
+	if provider.ClientConfig == nil {
+		provider.ClientConfig = client.GetDefaultConfig()
+		// XXX: remove the next 3 lines in v3.0.0
+		if provider.Insecure {
+			log.Println("WARNING: alerting.mattermost.insecure has been deprecated and will be removed in v3.0.0 in favor of alerting.mattermost.client.insecure")
+			provider.ClientConfig.Insecure = true
+		}
+	}
+	return len(provider.WebhookURL) > 0
+}
+
+// ToCustomAlertProvider converts the provider into a custom.AlertProvider
+func (provider *AlertProvider) ToCustomAlertProvider(service *core.Service, alert *alert.Alert, result *core.Result, resolved bool) *custom.AlertProvider {
+	var message string
+	var color string
+	if resolved {
+		message = fmt.Sprintf("An alert for *%s* has been resolved after passing successfully %d time(s) in a row", service.Name, alert.SuccessThreshold)
+		color = "#36A64F"
+	} else {
+		message = fmt.Sprintf("An alert for *%s* has been triggered due to having failed %d time(s) in a row", service.Name, alert.FailureThreshold)
+		color = "#DD0000"
+	}
+	var results string
+	for _, conditionResult := range result.ConditionResults {
+		var prefix string
+		if conditionResult.Success {
+			prefix = ":white_check_mark:"
+		} else {
+			prefix = ":x:"
+		}
+		results += fmt.Sprintf("%s - `%s`\\n", prefix, conditionResult.Condition)
+	}
+	var description string
+	if alertDescription := alert.GetDescription(); len(alertDescription) > 0 {
+		description = ":\\n> " + alertDescription
+	}
+	return &custom.AlertProvider{
+		URL:          provider.WebhookURL,
+		Method:       http.MethodPost,
+		ClientConfig: provider.ClientConfig,
+		Body: fmt.Sprintf(`{
+  "text": "",
+  "username": "gatus",
+  "icon_url": "https://raw.githubusercontent.com/TwinProduction/gatus/master/static/logo.png",
+  "attachments": [
+    {
+      "title": ":rescue_worker_helmet: Gatus",
+      "fallback": "Gatus - %s",
+      "text": "%s%s",
+      "short": false,
+      "color": "%s",
+      "fields": [
+        {
+          "title": "URL",
+          "value": "%s",
+          "short": false
+        },
+        {
+          "title": "Condition results",
+          "value": "%s",
+          "short": false
+        }
+      ]
+    }
+  ]
+}`, message, message, description, color, service.URL, results),
+		Headers: map[string]string{"Content-Type": "application/json"},
+	}
+}
+
+// GetDefaultAlert returns the provider's default alert configuration
+func (provider AlertProvider) GetDefaultAlert() *alert.Alert {
+	return provider.DefaultAlert
+}

alerting/provider/mattermost/mattermost_test.go

@@ -0,0 +1,70 @@
+package mattermost
+
+import (
+	"encoding/json"
+	"net/http"
+	"strings"
+	"testing"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/core"
+)
+
+func TestAlertProvider_IsValid(t *testing.T) {
+	invalidProvider := AlertProvider{WebhookURL: ""}
+	if invalidProvider.IsValid() {
+		t.Error("provider shouldn't have been valid")
+	}
+	validProvider := AlertProvider{WebhookURL: "http://example.com"}
+	if !validProvider.IsValid() {
+		t.Error("provider should've been valid")
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProviderWithResolvedAlert(t *testing.T) {
+	provider := AlertProvider{WebhookURL: "http://example.org"}
+	alertDescription := "test"
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{Name: "svc"}, &alert.Alert{Description: &alertDescription}, &core.Result{ConditionResults: []*core.ConditionResult{{Condition: "SUCCESSFUL_CONDITION", Success: true}}}, true)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if !strings.Contains(customAlertProvider.Body, "resolved") {
+		t.Error("customAlertProvider.Body should've contained the substring resolved")
+	}
+	if customAlertProvider.URL != "http://example.org" {
+		t.Errorf("expected URL to be %s, got %s", "http://example.org", customAlertProvider.URL)
+	}
+	if customAlertProvider.Method != http.MethodPost {
+		t.Errorf("expected method to be %s, got %s", http.MethodPost, customAlertProvider.Method)
+	}
+	body := make(map[string]interface{})
+	err := json.Unmarshal([]byte(customAlertProvider.Body), &body)
+	if err != nil {
+		t.Error("expected body to be valid JSON, got error:", err.Error())
+	}
+	if expected := "An alert for *svc* has been resolved after passing successfully 0 time(s) in a row:\n> test"; expected != body["attachments"].([]interface{})[0].(map[string]interface{})["text"] {
+		t.Errorf("expected $.attachments[0].description to be %s, got %s", expected, body["attachments"].([]interface{})[0].(map[string]interface{})["text"])
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProviderWithTriggeredAlert(t *testing.T) {
+	provider := AlertProvider{WebhookURL: "http://example.org"}
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{}, &alert.Alert{}, &core.Result{ConditionResults: []*core.ConditionResult{{Condition: "UNSUCCESSFUL_CONDITION", Success: false}}}, false)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if !strings.Contains(customAlertProvider.Body, "triggered") {
+		t.Error("customAlertProvider.Body should've contained the substring triggered")
+	}
+	if customAlertProvider.URL != "http://example.org" {
+		t.Errorf("expected URL to be %s, got %s", "http://example.org", customAlertProvider.URL)
+	}
+	if customAlertProvider.Method != http.MethodPost {
+		t.Errorf("expected method to be %s, got %s", http.MethodPost, customAlertProvider.Method)
+	}
+	body := make(map[string]interface{})
+	err := json.Unmarshal([]byte(customAlertProvider.Body), &body)
+	if err != nil {
+		t.Error("expected body to be valid JSON, got error:", err.Error())
+	}
+}

alerting/provider/messagebird/messagebird.go

@@ -0,0 +1,59 @@
+package messagebird
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/alerting/provider/custom"
+	"github.com/TwinProduction/gatus/core"
+)
+
+const (
+	restAPIURL = "https://rest.messagebird.com/messages"
+)
+
+// AlertProvider is the configuration necessary for sending an alert using Messagebird
+type AlertProvider struct {
+	AccessKey  string `yaml:"access-key"`
+	Originator string `yaml:"originator"`
+	Recipients string `yaml:"recipients"`
+
+	// DefaultAlert is the default alert configuration to use for services with an alert of the appropriate type
+	DefaultAlert *alert.Alert `yaml:"default-alert"`
+}
+
+// IsValid returns whether the provider's configuration is valid
+func (provider *AlertProvider) IsValid() bool {
+	return len(provider.AccessKey) > 0 && len(provider.Originator) > 0 && len(provider.Recipients) > 0
+}
+
+// ToCustomAlertProvider converts the provider into a custom.AlertProvider
+// Reference doc for messagebird https://developers.messagebird.com/api/sms-messaging/#send-outbound-sms
+func (provider *AlertProvider) ToCustomAlertProvider(service *core.Service, alert *alert.Alert, _ *core.Result, resolved bool) *custom.AlertProvider {
+	var message string
+	if resolved {
+		message = fmt.Sprintf("RESOLVED: %s - %s", service.Name, alert.GetDescription())
+	} else {
+		message = fmt.Sprintf("TRIGGERED: %s - %s", service.Name, alert.GetDescription())
+	}
+
+	return &custom.AlertProvider{
+		URL:    restAPIURL,
+		Method: http.MethodPost,
+		Body: fmt.Sprintf(`{
+  "originator": "%s",
+  "recipients": "%s",
+  "body": "%s"
+}`, provider.Originator, provider.Recipients, message),
+		Headers: map[string]string{
+			"Content-Type":  "application/json",
+			"Authorization": fmt.Sprintf("AccessKey %s", provider.AccessKey),
+		},
+	}
+}
+
+// GetDefaultAlert returns the provider's default alert configuration
+func (provider AlertProvider) GetDefaultAlert() *alert.Alert {
+	return provider.DefaultAlert
+}

alerting/provider/messagebird/messagebird_test.go

@@ -0,0 +1,78 @@
+package messagebird
+
+import (
+	"encoding/json"
+	"net/http"
+	"strings"
+	"testing"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/core"
+)
+
+func TestMessagebirdAlertProvider_IsValid(t *testing.T) {
+	invalidProvider := AlertProvider{}
+	if invalidProvider.IsValid() {
+		t.Error("provider shouldn't have been valid")
+	}
+	validProvider := AlertProvider{
+		AccessKey:  "1",
+		Originator: "1",
+		Recipients: "1",
+	}
+	if !validProvider.IsValid() {
+		t.Error("provider should've been valid")
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProviderWithResolvedAlert(t *testing.T) {
+	provider := AlertProvider{
+		AccessKey:  "1",
+		Originator: "1",
+		Recipients: "1",
+	}
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{}, &alert.Alert{}, &core.Result{}, true)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if !strings.Contains(customAlertProvider.Body, "RESOLVED") {
+		t.Error("customAlertProvider.Body should've contained the substring RESOLVED")
+	}
+	if customAlertProvider.URL != "https://rest.messagebird.com/messages" {
+		t.Errorf("expected URL to be %s, got %s", "https://rest.messagebird.com/messages", customAlertProvider.URL)
+	}
+	if customAlertProvider.Method != http.MethodPost {
+		t.Errorf("expected method to be %s, got %s", http.MethodPost, customAlertProvider.Method)
+	}
+	body := make(map[string]interface{})
+	err := json.Unmarshal([]byte(customAlertProvider.Body), &body)
+	if err != nil {
+		t.Error("expected body to be valid JSON, got error:", err.Error())
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProviderWithTriggeredAlert(t *testing.T) {
+	provider := AlertProvider{
+		AccessKey:  "1",
+		Originator: "1",
+		Recipients: "1",
+	}
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{}, &alert.Alert{}, &core.Result{}, false)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if !strings.Contains(customAlertProvider.Body, "TRIGGERED") {
+		t.Error("customAlertProvider.Body should've contained the substring TRIGGERED")
+	}
+	if customAlertProvider.URL != "https://rest.messagebird.com/messages" {
+		t.Errorf("expected URL to be %s, got %s", "https://rest.messagebird.com/messages", customAlertProvider.URL)
+	}
+	if customAlertProvider.Method != http.MethodPost {
+		t.Errorf("expected method to be %s, got %s", http.MethodPost, customAlertProvider.Method)
+	}
+	body := make(map[string]interface{})
+	err := json.Unmarshal([]byte(customAlertProvider.Body), &body)
+	if err != nil {
+		t.Error("expected body to be valid JSON, got error:", err.Error())
+	}
+}

alerting/provider/pagerduty/pagerduty.go

@@ -0,0 +1,65 @@
+package pagerduty
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/alerting/provider/custom"
+	"github.com/TwinProduction/gatus/core"
+)
+
+const (
+	restAPIURL = "https://events.pagerduty.com/v2/enqueue"
+)
+
+// AlertProvider is the configuration necessary for sending an alert using PagerDuty
+type AlertProvider struct {
+	IntegrationKey string `yaml:"integration-key"`
+
+	// DefaultAlert is the default alert configuration to use for services with an alert of the appropriate type
+	DefaultAlert *alert.Alert `yaml:"default-alert"`
+}
+
+// IsValid returns whether the provider's configuration is valid
+func (provider *AlertProvider) IsValid() bool {
+	return len(provider.IntegrationKey) == 32
+}
+
+// ToCustomAlertProvider converts the provider into a custom.AlertProvider
+//
+// relevant: https://developer.pagerduty.com/docs/events-api-v2/trigger-events/
+func (provider *AlertProvider) ToCustomAlertProvider(service *core.Service, alert *alert.Alert, _ *core.Result, resolved bool) *custom.AlertProvider {
+	var message, eventAction, resolveKey string
+	if resolved {
+		message = fmt.Sprintf("RESOLVED: %s - %s", service.Name, alert.GetDescription())
+		eventAction = "resolve"
+		resolveKey = alert.ResolveKey
+	} else {
+		message = fmt.Sprintf("TRIGGERED: %s - %s", service.Name, alert.GetDescription())
+		eventAction = "trigger"
+		resolveKey = ""
+	}
+	return &custom.AlertProvider{
+		URL:    restAPIURL,
+		Method: http.MethodPost,
+		Body: fmt.Sprintf(`{
+  "routing_key": "%s",
+  "dedup_key": "%s",
+  "event_action": "%s",
+  "payload": {
+    "summary": "%s",
+    "source": "%s",
+    "severity": "critical"
+  }
+}`, provider.IntegrationKey, resolveKey, eventAction, message, service.Name),
+		Headers: map[string]string{
+			"Content-Type": "application/json",
+		},
+	}
+}
+
+// GetDefaultAlert returns the provider's default alert configuration
+func (provider AlertProvider) GetDefaultAlert() *alert.Alert {
+	return provider.DefaultAlert
+}

alerting/provider/pagerduty/pagerduty_test.go

@@ -0,0 +1,66 @@
+package pagerduty
+
+import (
+	"encoding/json"
+	"net/http"
+	"strings"
+	"testing"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/core"
+)
+
+func TestAlertProvider_IsValid(t *testing.T) {
+	invalidProvider := AlertProvider{IntegrationKey: ""}
+	if invalidProvider.IsValid() {
+		t.Error("provider shouldn't have been valid")
+	}
+	validProvider := AlertProvider{IntegrationKey: "00000000000000000000000000000000"}
+	if !validProvider.IsValid() {
+		t.Error("provider should've been valid")
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProviderWithResolvedAlert(t *testing.T) {
+	provider := AlertProvider{IntegrationKey: "00000000000000000000000000000000"}
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{}, &alert.Alert{}, &core.Result{}, true)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if !strings.Contains(customAlertProvider.Body, "RESOLVED") {
+		t.Error("customAlertProvider.Body should've contained the substring RESOLVED")
+	}
+	if customAlertProvider.URL != "https://events.pagerduty.com/v2/enqueue" {
+		t.Errorf("expected URL to be %s, got %s", "https://events.pagerduty.com/v2/enqueue", customAlertProvider.URL)
+	}
+	if customAlertProvider.Method != http.MethodPost {
+		t.Errorf("expected method to be %s, got %s", http.MethodPost, customAlertProvider.Method)
+	}
+	body := make(map[string]interface{})
+	err := json.Unmarshal([]byte(customAlertProvider.Body), &body)
+	if err != nil {
+		t.Error("expected body to be valid JSON, got error:", err.Error())
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProviderWithTriggeredAlert(t *testing.T) {
+	provider := AlertProvider{IntegrationKey: "00000000000000000000000000000000"}
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{}, &alert.Alert{}, &core.Result{}, false)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if !strings.Contains(customAlertProvider.Body, "TRIGGERED") {
+		t.Error("customAlertProvider.Body should've contained the substring TRIGGERED")
+	}
+	if customAlertProvider.URL != "https://events.pagerduty.com/v2/enqueue" {
+		t.Errorf("expected URL to be %s, got %s", "https://events.pagerduty.com/v2/enqueue", customAlertProvider.URL)
+	}
+	if customAlertProvider.Method != http.MethodPost {
+		t.Errorf("expected method to be %s, got %s", http.MethodPost, customAlertProvider.Method)
+	}
+	body := make(map[string]interface{})
+	err := json.Unmarshal([]byte(customAlertProvider.Body), &body)
+	if err != nil {
+		t.Error("expected body to be valid JSON, got error:", err.Error())
+	}
+}

alerting/provider/provider.go

@@ -0,0 +1,62 @@
+package provider
+
+import (
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/alerting/provider/custom"
+	"github.com/TwinProduction/gatus/alerting/provider/discord"
+	"github.com/TwinProduction/gatus/alerting/provider/mattermost"
+	"github.com/TwinProduction/gatus/alerting/provider/messagebird"
+	"github.com/TwinProduction/gatus/alerting/provider/pagerduty"
+	"github.com/TwinProduction/gatus/alerting/provider/slack"
+	"github.com/TwinProduction/gatus/alerting/provider/teams"
+	"github.com/TwinProduction/gatus/alerting/provider/telegram"
+	"github.com/TwinProduction/gatus/alerting/provider/twilio"
+	"github.com/TwinProduction/gatus/core"
+)
+
+// AlertProvider is the interface that each providers should implement
+type AlertProvider interface {
+	// IsValid returns whether the provider's configuration is valid
+	IsValid() bool
+
+	// ToCustomAlertProvider converts the provider into a custom.AlertProvider
+	ToCustomAlertProvider(service *core.Service, alert *alert.Alert, result *core.Result, resolved bool) *custom.AlertProvider
+
+	// GetDefaultAlert returns the provider's default alert configuration
+	GetDefaultAlert() *alert.Alert
+}
+
+// ParseWithDefaultAlert parses a service alert by using the provider's default alert as a baseline
+func ParseWithDefaultAlert(providerDefaultAlert, serviceAlert *alert.Alert) {
+	if providerDefaultAlert == nil || serviceAlert == nil {
+		return
+	}
+	if serviceAlert.Enabled == nil {
+		serviceAlert.Enabled = providerDefaultAlert.Enabled
+	}
+	if serviceAlert.SendOnResolved == nil {
+		serviceAlert.SendOnResolved = providerDefaultAlert.SendOnResolved
+	}
+	if serviceAlert.Description == nil {
+		serviceAlert.Description = providerDefaultAlert.Description
+	}
+	if serviceAlert.FailureThreshold == 0 {
+		serviceAlert.FailureThreshold = providerDefaultAlert.FailureThreshold
+	}
+	if serviceAlert.SuccessThreshold == 0 {
+		serviceAlert.SuccessThreshold = providerDefaultAlert.SuccessThreshold
+	}
+}
+
+var (
+	// Validate interface implementation on compile
+	_ AlertProvider = (*custom.AlertProvider)(nil)
+	_ AlertProvider = (*discord.AlertProvider)(nil)
+	_ AlertProvider = (*mattermost.AlertProvider)(nil)
+	_ AlertProvider = (*messagebird.AlertProvider)(nil)
+	_ AlertProvider = (*pagerduty.AlertProvider)(nil)
+	_ AlertProvider = (*slack.AlertProvider)(nil)
+	_ AlertProvider = (*teams.AlertProvider)(nil)
+	_ AlertProvider = (*telegram.AlertProvider)(nil)
+	_ AlertProvider = (*twilio.AlertProvider)(nil)
+)

alerting/provider/provider_test.go

@@ -0,0 +1,153 @@
+package provider
+
+import (
+	"testing"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+)
+
+func TestParseWithDefaultAlert(t *testing.T) {
+	type Scenario struct {
+		Name                                            string
+		DefaultAlert, ServiceAlert, ExpectedOutputAlert *alert.Alert
+	}
+	enabled := true
+	disabled := false
+	firstDescription := "description-1"
+	secondDescription := "description-2"
+	scenarios := []Scenario{
+		{
+			Name: "service-alert-type-only",
+			DefaultAlert: &alert.Alert{
+				Enabled:          &enabled,
+				SendOnResolved:   &enabled,
+				Description:      &firstDescription,
+				FailureThreshold: 5,
+				SuccessThreshold: 10,
+			},
+			ServiceAlert: &alert.Alert{
+				Type: alert.TypeDiscord,
+			},
+			ExpectedOutputAlert: &alert.Alert{
+				Type:             alert.TypeDiscord,
+				Enabled:          &enabled,
+				SendOnResolved:   &enabled,
+				Description:      &firstDescription,
+				FailureThreshold: 5,
+				SuccessThreshold: 10,
+			},
+		},
+		{
+			Name: "service-alert-overwrites-default-alert",
+			DefaultAlert: &alert.Alert{
+				Enabled:          &disabled,
+				SendOnResolved:   &disabled,
+				Description:      &firstDescription,
+				FailureThreshold: 5,
+				SuccessThreshold: 10,
+			},
+			ServiceAlert: &alert.Alert{
+				Type:             alert.TypeTelegram,
+				Enabled:          &enabled,
+				SendOnResolved:   &enabled,
+				Description:      &secondDescription,
+				FailureThreshold: 6,
+				SuccessThreshold: 11,
+			},
+			ExpectedOutputAlert: &alert.Alert{
+				Type:             alert.TypeTelegram,
+				Enabled:          &enabled,
+				SendOnResolved:   &enabled,
+				Description:      &secondDescription,
+				FailureThreshold: 6,
+				SuccessThreshold: 11,
+			},
+		},
+		{
+			Name: "service-alert-partially-overwrites-default-alert",
+			DefaultAlert: &alert.Alert{
+				Enabled:          &enabled,
+				SendOnResolved:   &enabled,
+				Description:      &firstDescription,
+				FailureThreshold: 5,
+				SuccessThreshold: 10,
+			},
+			ServiceAlert: &alert.Alert{
+				Type:             alert.TypeDiscord,
+				Enabled:          nil,
+				SendOnResolved:   nil,
+				FailureThreshold: 6,
+				SuccessThreshold: 11,
+			},
+			ExpectedOutputAlert: &alert.Alert{
+				Type:             alert.TypeDiscord,
+				Enabled:          &enabled,
+				SendOnResolved:   &enabled,
+				Description:      &firstDescription,
+				FailureThreshold: 6,
+				SuccessThreshold: 11,
+			},
+		},
+		{
+			Name: "default-alert-type-should-be-ignored",
+			DefaultAlert: &alert.Alert{
+				Type:             alert.TypeTelegram,
+				Enabled:          &enabled,
+				SendOnResolved:   &enabled,
+				Description:      &firstDescription,
+				FailureThreshold: 5,
+				SuccessThreshold: 10,
+			},
+			ServiceAlert: &alert.Alert{
+				Type: alert.TypeDiscord,
+			},
+			ExpectedOutputAlert: &alert.Alert{
+				Type:             alert.TypeDiscord,
+				Enabled:          &enabled,
+				SendOnResolved:   &enabled,
+				Description:      &firstDescription,
+				FailureThreshold: 5,
+				SuccessThreshold: 10,
+			},
+		},
+		{
+			Name: "no-default-alert",
+			DefaultAlert: &alert.Alert{
+				Type:             alert.TypeDiscord,
+				Enabled:          nil,
+				SendOnResolved:   nil,
+				Description:      &firstDescription,
+				FailureThreshold: 2,
+				SuccessThreshold: 5,
+			},
+			ServiceAlert:        nil,
+			ExpectedOutputAlert: nil,
+		},
+	}
+	for _, scenario := range scenarios {
+		t.Run(scenario.Name, func(t *testing.T) {
+			ParseWithDefaultAlert(scenario.DefaultAlert, scenario.ServiceAlert)
+			if scenario.ExpectedOutputAlert == nil {
+				if scenario.ServiceAlert != nil {
+					t.Fail()
+				}
+				return
+			}
+			if scenario.ServiceAlert.IsEnabled() != scenario.ExpectedOutputAlert.IsEnabled() {
+				t.Errorf("expected ServiceAlert.IsEnabled() to be %v, got %v", scenario.ExpectedOutputAlert.IsEnabled(), scenario.ServiceAlert.IsEnabled())
+			}
+			if scenario.ServiceAlert.IsSendingOnResolved() != scenario.ExpectedOutputAlert.IsSendingOnResolved() {
+				t.Errorf("expected ServiceAlert.IsSendingOnResolved() to be %v, got %v", scenario.ExpectedOutputAlert.IsSendingOnResolved(), scenario.ServiceAlert.IsSendingOnResolved())
+			}
+			if scenario.ServiceAlert.GetDescription() != scenario.ExpectedOutputAlert.GetDescription() {
+				t.Errorf("expected ServiceAlert.GetDescription() to be %v, got %v", scenario.ExpectedOutputAlert.GetDescription(), scenario.ServiceAlert.GetDescription())
+			}
+			if scenario.ServiceAlert.FailureThreshold != scenario.ExpectedOutputAlert.FailureThreshold {
+				t.Errorf("expected ServiceAlert.FailureThreshold to be %v, got %v", scenario.ExpectedOutputAlert.FailureThreshold, scenario.ServiceAlert.FailureThreshold)
+			}
+			if scenario.ServiceAlert.SuccessThreshold != scenario.ExpectedOutputAlert.SuccessThreshold {
+				t.Errorf("expected ServiceAlert.SuccessThreshold to be %v, got %v", scenario.ExpectedOutputAlert.SuccessThreshold, scenario.ServiceAlert.SuccessThreshold)
+			}
+		})
+	}
+}

alerting/provider/slack/slack.go

@@ -0,0 +1,76 @@
+package slack
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/alerting/provider/custom"
+	"github.com/TwinProduction/gatus/core"
+)
+
+// AlertProvider is the configuration necessary for sending an alert using Slack
+type AlertProvider struct {
+	WebhookURL string `yaml:"webhook-url"` // Slack webhook URL
+
+	// DefaultAlert is the default alert configuration to use for services with an alert of the appropriate type
+	DefaultAlert *alert.Alert `yaml:"default-alert"`
+}
+
+// IsValid returns whether the provider's configuration is valid
+func (provider *AlertProvider) IsValid() bool {
+	return len(provider.WebhookURL) > 0
+}
+
+// ToCustomAlertProvider converts the provider into a custom.AlertProvider
+func (provider *AlertProvider) ToCustomAlertProvider(service *core.Service, alert *alert.Alert, result *core.Result, resolved bool) *custom.AlertProvider {
+	var message, color, results string
+	if resolved {
+		message = fmt.Sprintf("An alert for *%s* has been resolved after passing successfully %d time(s) in a row", service.Name, alert.SuccessThreshold)
+		color = "#36A64F"
+	} else {
+		message = fmt.Sprintf("An alert for *%s* has been triggered due to having failed %d time(s) in a row", service.Name, alert.FailureThreshold)
+		color = "#DD0000"
+	}
+	for _, conditionResult := range result.ConditionResults {
+		var prefix string
+		if conditionResult.Success {
+			prefix = ":white_check_mark:"
+		} else {
+			prefix = ":x:"
+		}
+		results += fmt.Sprintf("%s - `%s`\\n", prefix, conditionResult.Condition)
+	}
+	var description string
+	if alertDescription := alert.GetDescription(); len(alertDescription) > 0 {
+		description = ":\\n> " + alertDescription
+	}
+	return &custom.AlertProvider{
+		URL:    provider.WebhookURL,
+		Method: http.MethodPost,
+		Body: fmt.Sprintf(`{
+  "text": "",
+  "attachments": [
+    {
+      "title": ":helmet_with_white_cross: Gatus",
+      "text": "%s%s",
+      "short": false,
+      "color": "%s",
+      "fields": [
+        {
+          "title": "Condition results",
+          "value": "%s",
+          "short": false
+        }
+      ]
+    }
+  ]
+}`, message, description, color, results),
+		Headers: map[string]string{"Content-Type": "application/json"},
+	}
+}
+
+// GetDefaultAlert returns the provider's default alert configuration
+func (provider AlertProvider) GetDefaultAlert() *alert.Alert {
+	return provider.DefaultAlert
+}

alerting/provider/slack/slack_test.go

@@ -0,0 +1,70 @@
+package slack
+
+import (
+	"encoding/json"
+	"net/http"
+	"strings"
+	"testing"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/core"
+)
+
+func TestAlertProvider_IsValid(t *testing.T) {
+	invalidProvider := AlertProvider{WebhookURL: ""}
+	if invalidProvider.IsValid() {
+		t.Error("provider shouldn't have been valid")
+	}
+	validProvider := AlertProvider{WebhookURL: "http://example.com"}
+	if !validProvider.IsValid() {
+		t.Error("provider should've been valid")
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProviderWithResolvedAlert(t *testing.T) {
+	provider := AlertProvider{WebhookURL: "http://example.com"}
+	alertDescription := "test"
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{Name: "svc"}, &alert.Alert{Description: &alertDescription}, &core.Result{ConditionResults: []*core.ConditionResult{{Condition: "SUCCESSFUL_CONDITION", Success: true}}}, true)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if !strings.Contains(customAlertProvider.Body, "resolved") {
+		t.Error("customAlertProvider.Body should've contained the substring resolved")
+	}
+	if customAlertProvider.URL != "http://example.com" {
+		t.Errorf("expected URL to be %s, got %s", "http://example.com", customAlertProvider.URL)
+	}
+	if customAlertProvider.Method != http.MethodPost {
+		t.Errorf("expected method to be %s, got %s", http.MethodPost, customAlertProvider.Method)
+	}
+	body := make(map[string]interface{})
+	err := json.Unmarshal([]byte(customAlertProvider.Body), &body)
+	if err != nil {
+		t.Error("expected body to be valid JSON, got error:", err.Error())
+	}
+	if expected := "An alert for *svc* has been resolved after passing successfully 0 time(s) in a row:\n> test"; expected != body["attachments"].([]interface{})[0].(map[string]interface{})["text"] {
+		t.Errorf("expected $.attachments[0].description to be %s, got %s", expected, body["attachments"].([]interface{})[0].(map[string]interface{})["text"])
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProviderWithTriggeredAlert(t *testing.T) {
+	provider := AlertProvider{WebhookURL: "http://example.com"}
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{}, &alert.Alert{}, &core.Result{ConditionResults: []*core.ConditionResult{{Condition: "UNSUCCESSFUL_CONDITION", Success: false}}}, false)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if !strings.Contains(customAlertProvider.Body, "triggered") {
+		t.Error("customAlertProvider.Body should've contained the substring triggered")
+	}
+	if customAlertProvider.URL != "http://example.com" {
+		t.Errorf("expected URL to be %s, got %s", "http://example.com", customAlertProvider.URL)
+	}
+	if customAlertProvider.Method != http.MethodPost {
+		t.Errorf("expected method to be %s, got %s", http.MethodPost, customAlertProvider.Method)
+	}
+	body := make(map[string]interface{})
+	err := json.Unmarshal([]byte(customAlertProvider.Body), &body)
+	if err != nil {
+		t.Error("expected body to be valid JSON, got error:", err.Error())
+	}
+}

alerting/provider/teams/teams.go

@@ -0,0 +1,77 @@
+package teams
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/alerting/provider/custom"
+	"github.com/TwinProduction/gatus/core"
+)
+
+// AlertProvider is the configuration necessary for sending an alert using Teams
+type AlertProvider struct {
+	WebhookURL string `yaml:"webhook-url"`
+
+	// DefaultAlert is the default alert configuration to use for services with an alert of the appropriate type
+	DefaultAlert *alert.Alert `yaml:"default-alert"`
+}
+
+// IsValid returns whether the provider's configuration is valid
+func (provider *AlertProvider) IsValid() bool {
+	return len(provider.WebhookURL) > 0
+}
+
+// ToCustomAlertProvider converts the provider into a custom.AlertProvider
+func (provider *AlertProvider) ToCustomAlertProvider(service *core.Service, alert *alert.Alert, result *core.Result, resolved bool) *custom.AlertProvider {
+	var message string
+	var color string
+	if resolved {
+		message = fmt.Sprintf("An alert for *%s* has been resolved after passing successfully %d time(s) in a row", service.Name, alert.SuccessThreshold)
+		color = "#36A64F"
+	} else {
+		message = fmt.Sprintf("An alert for *%s* has been triggered due to having failed %d time(s) in a row", service.Name, alert.FailureThreshold)
+		color = "#DD0000"
+	}
+	var results string
+	for _, conditionResult := range result.ConditionResults {
+		var prefix string
+		if conditionResult.Success {
+			prefix = "✅"
+		} else {
+			prefix = "❌"
+		}
+		results += fmt.Sprintf("%s - `%s`<br/>", prefix, conditionResult.Condition)
+	}
+	var description string
+	if alertDescription := alert.GetDescription(); len(alertDescription) > 0 {
+		description = ":\\n> " + alertDescription
+	}
+	return &custom.AlertProvider{
+		URL:    provider.WebhookURL,
+		Method: http.MethodPost,
+		Body: fmt.Sprintf(`{
+  "@type": "MessageCard",
+  "@context": "http://schema.org/extensions",
+  "themeColor": "%s",
+  "title": "&#x1F6A8; Gatus",
+  "text": "%s%s",
+  "sections": [
+    {
+      "activityTitle": "URL",
+      "text": "%s"
+    },
+    {
+      "activityTitle": "Condition results",
+      "text": "%s"
+    }
+  ]
+}`, color, message, description, service.URL, results),
+		Headers: map[string]string{"Content-Type": "application/json"},
+	}
+}
+
+// GetDefaultAlert returns the provider's default alert configuration
+func (provider AlertProvider) GetDefaultAlert() *alert.Alert {
+	return provider.DefaultAlert
+}

alerting/provider/teams/teams_test.go

@@ -0,0 +1,70 @@
+package teams
+
+import (
+	"encoding/json"
+	"net/http"
+	"strings"
+	"testing"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/core"
+)
+
+func TestAlertProvider_IsValid(t *testing.T) {
+	invalidProvider := AlertProvider{WebhookURL: ""}
+	if invalidProvider.IsValid() {
+		t.Error("provider shouldn't have been valid")
+	}
+	validProvider := AlertProvider{WebhookURL: "http://example.com"}
+	if !validProvider.IsValid() {
+		t.Error("provider should've been valid")
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProviderWithResolvedAlert(t *testing.T) {
+	provider := AlertProvider{WebhookURL: "http://example.org"}
+	alertDescription := "test"
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{Name: "svc"}, &alert.Alert{Description: &alertDescription}, &core.Result{ConditionResults: []*core.ConditionResult{{Condition: "SUCCESSFUL_CONDITION", Success: true}}}, true)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if !strings.Contains(customAlertProvider.Body, "resolved") {
+		t.Error("customAlertProvider.Body should've contained the substring resolved")
+	}
+	if customAlertProvider.URL != "http://example.org" {
+		t.Errorf("expected URL to be %s, got %s", "http://example.org", customAlertProvider.URL)
+	}
+	if customAlertProvider.Method != http.MethodPost {
+		t.Errorf("expected method to be %s, got %s", http.MethodPost, customAlertProvider.Method)
+	}
+	body := make(map[string]interface{})
+	err := json.Unmarshal([]byte(customAlertProvider.Body), &body)
+	if err != nil {
+		t.Error("expected body to be valid JSON, got error:", err.Error())
+	}
+	if expected := "An alert for *svc* has been resolved after passing successfully 0 time(s) in a row:\n> test"; expected != body["text"] {
+		t.Errorf("expected $.text to be %s, got %s", expected, body["text"])
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProviderWithTriggeredAlert(t *testing.T) {
+	provider := AlertProvider{WebhookURL: "http://example.org"}
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{}, &alert.Alert{}, &core.Result{ConditionResults: []*core.ConditionResult{{Condition: "UNSUCCESSFUL_CONDITION", Success: false}}}, false)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if !strings.Contains(customAlertProvider.Body, "triggered") {
+		t.Error("customAlertProvider.Body should've contained the substring triggered")
+	}
+	if customAlertProvider.URL != "http://example.org" {
+		t.Errorf("expected URL to be %s, got %s", "http://example.org", customAlertProvider.URL)
+	}
+	if customAlertProvider.Method != http.MethodPost {
+		t.Errorf("expected method to be %s, got %s", http.MethodPost, customAlertProvider.Method)
+	}
+	body := make(map[string]interface{})
+	err := json.Unmarshal([]byte(customAlertProvider.Body), &body)
+	if err != nil {
+		t.Error("expected body to be valid JSON, got error:", err.Error())
+	}
+}

alerting/provider/telegram/telegram.go

@@ -0,0 +1,60 @@
+package telegram
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/alerting/provider/custom"
+	"github.com/TwinProduction/gatus/core"
+)
+
+// AlertProvider is the configuration necessary for sending an alert using Telegram
+type AlertProvider struct {
+	Token string `yaml:"token"`
+	ID    string `yaml:"id"`
+
+	// DefaultAlert is the default alert configuration to use for services with an alert of the appropriate type
+	DefaultAlert *alert.Alert `yaml:"default-alert"`
+}
+
+// IsValid returns whether the provider's configuration is valid
+func (provider *AlertProvider) IsValid() bool {
+	return len(provider.Token) > 0 && len(provider.ID) > 0
+}
+
+// ToCustomAlertProvider converts the provider into a custom.AlertProvider
+func (provider *AlertProvider) ToCustomAlertProvider(service *core.Service, alert *alert.Alert, result *core.Result, resolved bool) *custom.AlertProvider {
+	var message, results string
+	if resolved {
+		message = fmt.Sprintf("An alert for *%s* has been resolved:\\n—\\n    _healthcheck passing successfully %d time(s) in a row_\\n—  ", service.Name, alert.FailureThreshold)
+	} else {
+		message = fmt.Sprintf("An alert for *%s* has been triggered:\\n—\\n    _healthcheck failed %d time(s) in a row_\\n—  ", service.Name, alert.FailureThreshold)
+	}
+	for _, conditionResult := range result.ConditionResults {
+		var prefix string
+		if conditionResult.Success {
+			prefix = "✅"
+		} else {
+			prefix = "❌"
+		}
+		results += fmt.Sprintf("%s - `%s`\\n", prefix, conditionResult.Condition)
+	}
+	var text string
+	if len(alert.GetDescription()) > 0 {
+		text = fmt.Sprintf("⛑ *Gatus* \\n%s \\n*Description* \\n_%s_  \\n\\n*Condition results*\\n%s", message, alert.GetDescription(), results)
+	} else {
+		text = fmt.Sprintf("⛑ *Gatus* \\n%s \\n*Condition results*\\n%s", message, results)
+	}
+	return &custom.AlertProvider{
+		URL:     fmt.Sprintf("https://api.telegram.org/bot%s/sendMessage", provider.Token),
+		Method:  http.MethodPost,
+		Body:    fmt.Sprintf(`{"chat_id": "%s", "text": "%s", "parse_mode": "MARKDOWN"}`, provider.ID, text),
+		Headers: map[string]string{"Content-Type": "application/json"},
+	}
+}
+
+// GetDefaultAlert returns the provider's default alert configuration
+func (provider AlertProvider) GetDefaultAlert() *alert.Alert {
+	return provider.DefaultAlert
+}

alerting/provider/telegram/telegram_test.go

@@ -0,0 +1,91 @@
+package telegram
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strings"
+	"testing"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/core"
+)
+
+func TestAlertProvider_IsValid(t *testing.T) {
+	invalidProvider := AlertProvider{Token: "", ID: ""}
+	if invalidProvider.IsValid() {
+		t.Error("provider shouldn't have been valid")
+	}
+	validProvider := AlertProvider{Token: "123456:ABC-DEF1234ghIkl-zyx57W2v1u123ew11", ID: "12345678"}
+	if !validProvider.IsValid() {
+		t.Error("provider should've been valid")
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProviderWithResolvedAlert(t *testing.T) {
+	provider := AlertProvider{Token: "123456:ABC-DEF1234ghIkl-zyx57W2v1u123ew11", ID: "12345678"}
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{}, &alert.Alert{}, &core.Result{ConditionResults: []*core.ConditionResult{{Condition: "SUCCESSFUL_CONDITION", Success: true}}}, true)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if !strings.Contains(customAlertProvider.Body, "resolved") {
+		t.Error("customAlertProvider.Body should've contained the substring resolved")
+	}
+	if customAlertProvider.URL != fmt.Sprintf("https://api.telegram.org/bot%s/sendMessage", provider.Token) {
+		t.Errorf("expected URL to be %s, got %s", fmt.Sprintf("https://api.telegram.org/bot%s/sendMessage", provider.Token), customAlertProvider.URL)
+	}
+	if customAlertProvider.Method != http.MethodPost {
+		t.Errorf("expected method to be %s, got %s", http.MethodPost, customAlertProvider.Method)
+	}
+	body := make(map[string]interface{})
+	err := json.Unmarshal([]byte(customAlertProvider.Body), &body)
+	//_, err := json.Marshal(customAlertProvider.Body)
+	if err != nil {
+		t.Error("expected body to be valid JSON, got error:", err.Error())
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProviderWithTriggeredAlert(t *testing.T) {
+	provider := AlertProvider{Token: "123456:ABC-DEF1234ghIkl-zyx57W2v1u123ew11", ID: "0123456789"}
+	description := "Healthcheck Successful"
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{}, &alert.Alert{Description: &description}, &core.Result{ConditionResults: []*core.ConditionResult{{Condition: "UNSUCCESSFUL_CONDITION", Success: false}}}, false)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if !strings.Contains(customAlertProvider.Body, "triggered") {
+		t.Error("customAlertProvider.Body should've contained the substring triggered")
+	}
+	if customAlertProvider.URL != fmt.Sprintf("https://api.telegram.org/bot%s/sendMessage", provider.Token) {
+		t.Errorf("expected URL to be %s, got %s", fmt.Sprintf("https://api.telegram.org/bot%s/sendMessage", provider.Token), customAlertProvider.URL)
+	}
+	if customAlertProvider.Method != http.MethodPost {
+		t.Errorf("expected method to be %s, got %s", http.MethodPost, customAlertProvider.Method)
+	}
+	body := make(map[string]interface{})
+	err := json.Unmarshal([]byte(customAlertProvider.Body), &body)
+	if err != nil {
+		t.Error("expected body to be valid JSON, got error:", err.Error())
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProviderWithDescription(t *testing.T) {
+	provider := AlertProvider{Token: "123456:ABC-DEF1234ghIkl-zyx57W2v1u123ew11", ID: "0123456789"}
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{}, &alert.Alert{}, &core.Result{ConditionResults: []*core.ConditionResult{{Condition: "UNSUCCESSFUL_CONDITION", Success: false}}}, false)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if !strings.Contains(customAlertProvider.Body, "triggered") {
+		t.Error("customAlertProvider.Body should've contained the substring triggered")
+	}
+	if customAlertProvider.URL != fmt.Sprintf("https://api.telegram.org/bot%s/sendMessage", provider.Token) {
+		t.Errorf("expected URL to be %s, got %s", fmt.Sprintf("https://api.telegram.org/bot%s/sendMessage", provider.Token), customAlertProvider.URL)
+	}
+	if customAlertProvider.Method != http.MethodPost {
+		t.Errorf("expected method to be %s, got %s", http.MethodPost, customAlertProvider.Method)
+	}
+	body := make(map[string]interface{})
+	err := json.Unmarshal([]byte(customAlertProvider.Body), &body)
+	if err != nil {
+		t.Error("expected body to be valid JSON, got error:", err.Error())
+	}
+}

alerting/provider/twilio/twilio.go

@@ -0,0 +1,56 @@
+package twilio
+
+import (
+	"encoding/base64"
+	"fmt"
+	"net/http"
+	"net/url"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/alerting/provider/custom"
+	"github.com/TwinProduction/gatus/core"
+)
+
+// AlertProvider is the configuration necessary for sending an alert using Twilio
+type AlertProvider struct {
+	SID   string `yaml:"sid"`
+	Token string `yaml:"token"`
+	From  string `yaml:"from"`
+	To    string `yaml:"to"`
+
+	// DefaultAlert is the default alert configuration to use for services with an alert of the appropriate type
+	DefaultAlert *alert.Alert `yaml:"default-alert"`
+}
+
+// IsValid returns whether the provider's configuration is valid
+func (provider *AlertProvider) IsValid() bool {
+	return len(provider.Token) > 0 && len(provider.SID) > 0 && len(provider.From) > 0 && len(provider.To) > 0
+}
+
+// ToCustomAlertProvider converts the provider into a custom.AlertProvider
+func (provider *AlertProvider) ToCustomAlertProvider(service *core.Service, alert *alert.Alert, _ *core.Result, resolved bool) *custom.AlertProvider {
+	var message string
+	if resolved {
+		message = fmt.Sprintf("RESOLVED: %s - %s", service.Name, alert.GetDescription())
+	} else {
+		message = fmt.Sprintf("TRIGGERED: %s - %s", service.Name, alert.GetDescription())
+	}
+	return &custom.AlertProvider{
+		URL:    fmt.Sprintf("https://api.twilio.com/2010-04-01/Accounts/%s/Messages.json", provider.SID),
+		Method: http.MethodPost,
+		Body: url.Values{
+			"To":   {provider.To},
+			"From": {provider.From},
+			"Body": {message},
+		}.Encode(),
+		Headers: map[string]string{
+			"Content-Type":  "application/x-www-form-urlencoded",
+			"Authorization": fmt.Sprintf("Basic %s", base64.StdEncoding.EncodeToString([]byte(fmt.Sprintf("%s:%s", provider.SID, provider.Token)))),
+		},
+	}
+}
+
+// GetDefaultAlert returns the provider's default alert configuration
+func (provider AlertProvider) GetDefaultAlert() *alert.Alert {
+	return provider.DefaultAlert
+}

alerting/provider/twilio/twilio_test.go

@@ -0,0 +1,78 @@
+package twilio
+
+import (
+	"net/http"
+	"strings"
+	"testing"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/core"
+)
+
+func TestTwilioAlertProvider_IsValid(t *testing.T) {
+	invalidProvider := AlertProvider{}
+	if invalidProvider.IsValid() {
+		t.Error("provider shouldn't have been valid")
+	}
+	validProvider := AlertProvider{
+		SID:   "1",
+		Token: "1",
+		From:  "1",
+		To:    "1",
+	}
+	if !validProvider.IsValid() {
+		t.Error("provider should've been valid")
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProviderWithResolvedAlert(t *testing.T) {
+	provider := AlertProvider{
+		SID:   "1",
+		Token: "2",
+		From:  "3",
+		To:    "4",
+	}
+	description := "alert-description"
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{Name: "service-name"}, &alert.Alert{Description: &description}, &core.Result{}, true)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if !strings.Contains(customAlertProvider.Body, "RESOLVED") {
+		t.Error("customAlertProvider.Body should've contained the substring RESOLVED")
+	}
+	if customAlertProvider.URL != "https://api.twilio.com/2010-04-01/Accounts/1/Messages.json" {
+		t.Errorf("expected URL to be %s, got %s", "https://api.twilio.com/2010-04-01/Accounts/1/Messages.json", customAlertProvider.URL)
+	}
+	if customAlertProvider.Method != http.MethodPost {
+		t.Errorf("expected method to be %s, got %s", http.MethodPost, customAlertProvider.Method)
+	}
+	if customAlertProvider.Body != "Body=RESOLVED%3A+service-name+-+alert-description&From=3&To=4" {
+		t.Errorf("expected body to be %s, got %s", "Body=RESOLVED%3A+service-name+-+alert-description&From=3&To=4", customAlertProvider.Body)
+	}
+}
+
+func TestAlertProvider_ToCustomAlertProviderWithTriggeredAlert(t *testing.T) {
+	provider := AlertProvider{
+		SID:   "4",
+		Token: "3",
+		From:  "2",
+		To:    "1",
+	}
+	description := "alert-description"
+	customAlertProvider := provider.ToCustomAlertProvider(&core.Service{Name: "service-name"}, &alert.Alert{Description: &description}, &core.Result{}, false)
+	if customAlertProvider == nil {
+		t.Fatal("customAlertProvider shouldn't have been nil")
+	}
+	if !strings.Contains(customAlertProvider.Body, "TRIGGERED") {
+		t.Error("customAlertProvider.Body should've contained the substring TRIGGERED")
+	}
+	if customAlertProvider.URL != "https://api.twilio.com/2010-04-01/Accounts/4/Messages.json" {
+		t.Errorf("expected URL to be %s, got %s", "https://api.twilio.com/2010-04-01/Accounts/4/Messages.json", customAlertProvider.URL)
+	}
+	if customAlertProvider.Method != http.MethodPost {
+		t.Errorf("expected method to be %s, got %s", http.MethodPost, customAlertProvider.Method)
+	}
+	if customAlertProvider.Body != "Body=TRIGGERED%3A+service-name+-+alert-description&From=2&To=1" {
+		t.Errorf("expected body to be %s, got %s", "Body=TRIGGERED%3A+service-name+-+alert-description&From=2&To=1", customAlertProvider.Body)
+	}
+}

client/client.go

@@ -0,0 +1,85 @@
+package client
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"errors"
+	"net"
+	"net/http"
+	"net/smtp"
+	"runtime"
+	"strings"
+	"time"
+
+	"github.com/go-ping/ping"
+)
+
+// GetHTTPClient returns the shared HTTP client
+func GetHTTPClient(config *Config) *http.Client {
+	if config == nil {
+		return defaultConfig.getHTTPClient()
+	}
+	return config.getHTTPClient()
+}
+
+// CanCreateTCPConnection checks whether a connection can be established with a TCP service
+func CanCreateTCPConnection(address string, config *Config) bool {
+	conn, err := net.DialTimeout("tcp", address, config.Timeout)
+	if err != nil {
+		return false
+	}
+	_ = conn.Close()
+	return true
+}
+
+// CanPerformStartTLS checks whether a connection can be established to an address using the STARTTLS protocol
+func CanPerformStartTLS(address string, config *Config) (connected bool, certificate *x509.Certificate, err error) {
+	hostAndPort := strings.Split(address, ":")
+	if len(hostAndPort) != 2 {
+		return false, nil, errors.New("invalid address for starttls, format must be host:port")
+	}
+	smtpClient, err := smtp.Dial(address)
+	if err != nil {
+		return
+	}
+	err = smtpClient.StartTLS(&tls.Config{
+		InsecureSkipVerify: config.Insecure,
+		ServerName:         hostAndPort[0],
+	})
+	if err != nil {
+		return
+	}
+	if state, ok := smtpClient.TLSConnectionState(); ok {
+		certificate = state.PeerCertificates[0]
+	} else {
+		return false, nil, errors.New("could not get TLS connection state")
+	}
+	return true, certificate, nil
+}
+
+// Ping checks if an address can be pinged and returns the round-trip time if the address can be pinged
+//
+// Note that this function takes at least 100ms, even if the address is 127.0.0.1
+func Ping(address string, config *Config) (bool, time.Duration) {
+	pinger, err := ping.NewPinger(address)
+	if err != nil {
+		return false, 0
+	}
+	pinger.Count = 1
+	pinger.Timeout = config.Timeout
+	// Set the pinger's privileged mode to true for every operating system except darwin
+	// https://github.com/TwinProduction/gatus/issues/132
+	pinger.SetPrivileged(runtime.GOOS != "darwin")
+	err = pinger.Run()
+	if err != nil {
+		return false, 0
+	}
+	if pinger.Statistics() != nil {
+		// If the packet loss is 100, it means that the packet didn't reach the host
+		if pinger.Statistics().PacketLoss == 100 {
+			return false, pinger.Timeout
+		}
+		return true, pinger.Statistics().MaxRtt
+	}
+	return true, 0
+}

client/client_test.go

@@ -0,0 +1,98 @@
+package client
+
+import (
+	"testing"
+	"time"
+)
+
+func TestGetHTTPClient(t *testing.T) {
+	cfg := &Config{
+		Insecure:       false,
+		IgnoreRedirect: false,
+		Timeout:        0,
+	}
+	cfg.ValidateAndSetDefaults()
+	if GetHTTPClient(cfg) == nil {
+		t.Error("expected client to not be nil")
+	}
+	if GetHTTPClient(nil) == nil {
+		t.Error("expected client to not be nil")
+	}
+}
+
+func TestPing(t *testing.T) {
+	if success, rtt := Ping("127.0.0.1", &Config{Timeout: 500 * time.Millisecond}); !success {
+		t.Error("expected true")
+		if rtt == 0 {
+			t.Error("Round-trip time returned on success should've higher than 0")
+		}
+	}
+	if success, rtt := Ping("256.256.256.256", &Config{Timeout: 500 * time.Millisecond}); success {
+		t.Error("expected false, because the IP is invalid")
+		if rtt != 0 {
+			t.Error("Round-trip time returned on failure should've been 0")
+		}
+	}
+	if success, rtt := Ping("192.168.152.153", &Config{Timeout: 500 * time.Millisecond}); success {
+		t.Error("expected false, because the IP is valid but the host should be unreachable")
+		if rtt != 0 {
+			t.Error("Round-trip time returned on failure should've been 0")
+		}
+	}
+}
+
+func TestCanPerformStartTLS(t *testing.T) {
+	type args struct {
+		address  string
+		insecure bool
+	}
+	tests := []struct {
+		name          string
+		args          args
+		wantConnected bool
+		wantErr       bool
+	}{
+		{
+			name: "invalid address",
+			args: args{
+				address: "test",
+			},
+			wantConnected: false,
+			wantErr:       true,
+		},
+		{
+			name: "error dial",
+			args: args{
+				address: "test:1234",
+			},
+			wantConnected: false,
+			wantErr:       true,
+		},
+		{
+			name: "valid starttls",
+			args: args{
+				address: "smtp.gmail.com:587",
+			},
+			wantConnected: true,
+			wantErr:       false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			connected, _, err := CanPerformStartTLS(tt.args.address, &Config{Insecure: tt.args.insecure, Timeout: 5 * time.Second})
+			if (err != nil) != tt.wantErr {
+				t.Errorf("CanPerformStartTLS() err=%v, wantErr=%v", err, tt.wantErr)
+				return
+			}
+			if connected != tt.wantConnected {
+				t.Errorf("CanPerformStartTLS() connected=%v, wantConnected=%v", connected, tt.wantConnected)
+			}
+		})
+	}
+}
+
+func TestCanCreateTCPConnection(t *testing.T) {
+	if CanCreateTCPConnection("127.0.0.1", &Config{Timeout: 5 * time.Second}) {
+		t.Error("should've failed, because there's no port in the address")
+	}
+}

client/config.go

@@ -0,0 +1,73 @@
+package client
+
+import (
+	"crypto/tls"
+	"net/http"
+	"time"
+)
+
+const (
+	defaultHTTPTimeout = 10 * time.Second
+)
+
+var (
+	// DefaultConfig is the default client configuration
+	defaultConfig = Config{
+		Insecure:       false,
+		IgnoreRedirect: false,
+		Timeout:        defaultHTTPTimeout,
+	}
+)
+
+// GetDefaultConfig returns a copy of the default configuration
+func GetDefaultConfig() *Config {
+	cfg := defaultConfig
+	return &cfg
+}
+
+// Config is the configuration for clients
+type Config struct {
+	// Insecure determines whether to skip verifying the server's certificate chain and host name
+	Insecure bool `yaml:"insecure"`
+
+	// IgnoreRedirect determines whether to ignore redirects (true) or follow them (false, default)
+	IgnoreRedirect bool `yaml:"ignore-redirect"`
+
+	// Timeout for the client
+	Timeout time.Duration `yaml:"timeout"`
+
+	httpClient *http.Client
+}
+
+// ValidateAndSetDefaults validates the client configuration and sets the default values if necessary
+func (c *Config) ValidateAndSetDefaults() {
+	if c.Timeout < time.Millisecond {
+		c.Timeout = 10 * time.Second
+	}
+}
+
+// GetHTTPClient return a HTTP client matching the Config's parameters.
+func (c *Config) getHTTPClient() *http.Client {
+	if c.httpClient == nil {
+		c.httpClient = &http.Client{
+			Timeout: c.Timeout,
+			Transport: &http.Transport{
+				MaxIdleConns:        100,
+				MaxIdleConnsPerHost: 20,
+				Proxy:               http.ProxyFromEnvironment,
+				TLSClientConfig: &tls.Config{
+					InsecureSkipVerify: c.Insecure,
+				},
+			},
+			CheckRedirect: func(req *http.Request, via []*http.Request) error {
+				if c.IgnoreRedirect {
+					// Don't follow redirects
+					return http.ErrUseLastResponse
+				}
+				// Follow redirects
+				return nil
+			},
+		}
+	}
+	return c.httpClient
+}

client/config_test.go

@@ -0,0 +1,37 @@
+package client
+
+import (
+	"net/http"
+	"testing"
+	"time"
+)
+
+func TestConfig_getHTTPClient(t *testing.T) {
+	insecureConfig := &Config{Insecure: true}
+	insecureConfig.ValidateAndSetDefaults()
+	insecureClient := insecureConfig.getHTTPClient()
+	if !(insecureClient.Transport).(*http.Transport).TLSClientConfig.InsecureSkipVerify {
+		t.Error("expected Config.Insecure set to true to cause the HTTP client to skip certificate verification")
+	}
+	if insecureClient.Timeout != defaultHTTPTimeout {
+		t.Error("expected Config.Timeout to default the HTTP client to a timeout of 10s")
+	}
+	request, _ := http.NewRequest("GET", "", nil)
+	if err := insecureClient.CheckRedirect(request, nil); err != nil {
+		t.Error("expected Config.IgnoreRedirect set to false to cause the HTTP client's CheckRedirect to return nil")
+	}
+
+	secureConfig := &Config{IgnoreRedirect: true, Timeout: 5 * time.Second}
+	secureConfig.ValidateAndSetDefaults()
+	secureClient := secureConfig.getHTTPClient()
+	if (secureClient.Transport).(*http.Transport).TLSClientConfig.InsecureSkipVerify {
+		t.Error("expected Config.Insecure set to false to cause the HTTP client to not skip certificate verification")
+	}
+	if secureClient.Timeout != 5*time.Second {
+		t.Error("expected Config.Timeout to cause the HTTP client to have a timeout of 5s")
+	}
+	request, _ = http.NewRequest("GET", "", nil)
+	if err := secureClient.CheckRedirect(request, nil); err != http.ErrUseLastResponse {
+		t.Error("expected Config.IgnoreRedirect set to true to cause the HTTP client's CheckRedirect to return http.ErrUseLastResponse")
+	}
+}

config.yaml

@@ -1,11 +1,47 @@
-metrics: true
 services:
-  - name: twinnation
-    url: https://twinnation.org/actuator/health
-    interval: 15s
+  - name: front-end
+    group: core
+    url: "https://twinnation.org/health"
+    interval: 1m
     conditions:
       - "[STATUS] == 200"
-  - name: github
-    url: https://api.github.com/healthz
+      - "[BODY].status == UP"
+      - "[RESPONSE_TIME] < 150"
+
+  - name: back-end
+    group: core
+    url: "https://example.org/"
+    interval: 5m
     conditions:
-      - "[STATUS] == 200"
+      - "[STATUS] == 200"
+      - "[CERTIFICATE_EXPIRATION] > 48h"
+
+  - name: monitoring
+    group: internal
+    url: "https://example.org/"
+    interval: 5m
+    conditions:
+      - "[STATUS] == 200"
+
+  - name: nas
+    group: internal
+    url: "https://example.org/"
+    interval: 5m
+    conditions:
+      - "[STATUS] == 200"
+
+  - name: example-dns-query
+    url: "8.8.8.8" # Address of the DNS server to use
+    interval: 5m
+    dns:
+      query-name: "example.com"
+      query-type: "A"
+    conditions:
+      - "[BODY] == 93.184.216.34"
+      - "[DNS_RCODE] == NOERROR"
+
+  - name: icmp-ping
+    url: "icmp://example.org"
+    interval: 1m
+    conditions:
+      - "[CONNECTED] == true"

config/config.go

@@ -2,56 +2,133 @@ package config
 
 import (
 	"errors"
-	"github.com/TwinProduction/gatus/core"
-	"gopkg.in/yaml.v2"
 	"io/ioutil"
 	"log"
 	"os"
 	"time"
+
+	"github.com/TwinProduction/gatus/alerting"
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/alerting/provider"
+	"github.com/TwinProduction/gatus/core"
+	"github.com/TwinProduction/gatus/k8s"
+	"github.com/TwinProduction/gatus/security"
+	"github.com/TwinProduction/gatus/storage"
+	"gopkg.in/yaml.v2"
 )
 
-type Config struct {
-	Metrics  bool            `yaml:"metrics"`
-	Services []*core.Service `yaml:"services"`
-}
+const (
+	// DefaultConfigurationFilePath is the default path that will be used to search for the configuration file
+	// if a custom path isn't configured through the GATUS_CONFIG_FILE environment variable
+	DefaultConfigurationFilePath = "config/config.yaml"
+
+	// DefaultFallbackConfigurationFilePath is the default fallback path that will be used to search for the
+	// configuration file if DefaultConfigurationFilePath didn't work
+	DefaultFallbackConfigurationFilePath = "config/config.yml"
+
+	// DefaultAddress is the default address the service will bind to
+	DefaultAddress = "0.0.0.0"
+
+	// DefaultPort is the default port the service will listen on
+	DefaultPort = 8080
+)
 
 var (
-	ErrNoServiceInConfig  = errors.New("configuration file should contain at least 1 service")
+	// ErrNoServiceInConfig is an error returned when a configuration file has no services configured
+	ErrNoServiceInConfig = errors.New("configuration file should contain at least 1 service")
+
+	// ErrConfigFileNotFound is an error returned when the configuration file could not be found
 	ErrConfigFileNotFound = errors.New("configuration file not found")
-	ErrConfigNotLoaded    = errors.New("configuration is nil")
-	config                *Config
+
+	// ErrInvalidSecurityConfig is an error returned when the security configuration is invalid
+	ErrInvalidSecurityConfig = errors.New("invalid security configuration")
 )
 
-func Get() *Config {
-	if config == nil {
-		panic(ErrConfigNotLoaded)
-	}
-	return config
+// Config is the main configuration structure
+type Config struct {
+	// Debug Whether to enable debug logs
+	Debug bool `yaml:"debug"`
+
+	// Metrics Whether to expose metrics at /metrics
+	Metrics bool `yaml:"metrics"`
+
+	// SkipInvalidConfigUpdate Whether to make the application ignore invalid configuration
+	// if the configuration file is updated while the application is running
+	SkipInvalidConfigUpdate bool `yaml:"skip-invalid-config-update"`
+
+	// DisableMonitoringLock Whether to disable the monitoring lock
+	// The monitoring lock is what prevents multiple services from being processed at the same time.
+	// Disabling this may lead to inaccurate response times
+	DisableMonitoringLock bool `yaml:"disable-monitoring-lock"`
+
+	// Security Configuration for securing access to Gatus
+	Security *security.Config `yaml:"security"`
+
+	// Alerting Configuration for alerting
+	Alerting *alerting.Config `yaml:"alerting"`
+
+	// Services List of services to monitor
+	Services []*core.Service `yaml:"services"`
+
+	// Kubernetes is the Kubernetes configuration
+	Kubernetes *k8s.Config `yaml:"kubernetes"`
+
+	// Storage is the configuration for how the data is stored
+	Storage *storage.Config `yaml:"storage"`
+
+	// Web is the configuration for the web listener
+	Web *WebConfig `yaml:"web"`
+
+	filePath        string    // path to the file from which config was loaded from
+	lastFileModTime time.Time // last modification time
 }
 
-func Load(configFile string) error {
-	log.Printf("[config][Load] Attempting to load config from configFile=%s", configFile)
+// HasLoadedConfigurationFileBeenModified returns whether the file that the
+// configuration has been loaded from has been modified since it was last read
+func (config Config) HasLoadedConfigurationFileBeenModified() bool {
+	if fileInfo, err := os.Stat(config.filePath); err == nil {
+		if !fileInfo.ModTime().IsZero() {
+			return config.lastFileModTime.Unix() != fileInfo.ModTime().Unix()
+		}
+	}
+	return false
+}
+
+// UpdateLastFileModTime refreshes Config.lastFileModTime
+func (config *Config) UpdateLastFileModTime() {
+	if fileInfo, err := os.Stat(config.filePath); err == nil {
+		if !fileInfo.ModTime().IsZero() {
+			config.lastFileModTime = fileInfo.ModTime()
+		}
+	}
+}
+
+// Load loads a custom configuration file
+// Note that the misconfiguration of some fields may lead to panics. This is on purpose.
+func Load(configFile string) (*Config, error) {
+	log.Printf("[config][Load] Reading configuration from configFile=%s", configFile)
 	cfg, err := readConfigurationFile(configFile)
 	if err != nil {
 		if os.IsNotExist(err) {
-			return ErrConfigFileNotFound
-		} else {
-			return err
+			return nil, ErrConfigFileNotFound
 		}
+		return nil, err
 	}
-	config = cfg
-	return nil
+	cfg.filePath = configFile
+	cfg.UpdateLastFileModTime()
+	return cfg, nil
 }
 
-func LoadDefaultConfiguration() error {
-	err := Load("config/config.yaml")
+// LoadDefaultConfiguration loads the default configuration file
+func LoadDefaultConfiguration() (*Config, error) {
+	cfg, err := Load(DefaultConfigurationFilePath)
 	if err != nil {
 		if err == ErrConfigFileNotFound {
-			return Load("config/config.yml")
+			return Load(DefaultFallbackConfigurationFilePath)
 		}
-		return err
+		return nil, err
 	}
-	return nil
+	return cfg, nil
 }
 
 func readConfigurationFile(fileName string) (config *Config, err error) {
@@ -68,16 +145,161 @@ func parseAndValidateConfigBytes(yamlBytes []byte) (config *Config, err error) {
 	yamlBytes = []byte(os.ExpandEnv(string(yamlBytes)))
 	// Parse configuration file
 	err = yaml.Unmarshal(yamlBytes, &config)
-	// Check if the configuration file at least has services.
-	if config == nil || len(config.Services) == 0 {
+	if err != nil {
+		return
+	}
+	// Check if the configuration file at least has services configured or Kubernetes auto discovery enabled
+	if config == nil || ((config.Services == nil || len(config.Services) == 0) && (config.Kubernetes == nil || !config.Kubernetes.AutoDiscover)) {
 		err = ErrNoServiceInConfig
 	} else {
-		// Set the default values if they aren't set
-		for _, service := range config.Services {
-			if service.Interval == 0 {
-				service.Interval = 10 * time.Second
-			}
+		// Note that the functions below may panic, and this is on purpose to prevent Gatus from starting with
+		// invalid configurations
+		validateAlertingConfig(config.Alerting, config.Services, config.Debug)
+		if err := validateSecurityConfig(config); err != nil {
+			return nil, err
+		}
+		if err := validateServicesConfig(config); err != nil {
+			return nil, err
+		}
+		if err := validateKubernetesConfig(config); err != nil {
+			return nil, err
+		}
+		if err := validateWebConfig(config); err != nil {
+			return nil, err
+		}
+		if err := validateStorageConfig(config); err != nil {
+			return nil, err
 		}
 	}
 	return
 }
+
+func validateStorageConfig(config *Config) error {
+	if config.Storage == nil {
+		config.Storage = &storage.Config{
+			Type: storage.TypeMemory,
+		}
+	}
+	err := storage.Initialize(config.Storage)
+	if err != nil {
+		return err
+	}
+	// Remove all ServiceStatus that represent services which no longer exist in the configuration
+	var keys []string
+	for _, service := range config.Services {
+		keys = append(keys, service.Key())
+	}
+	numberOfServiceStatusesDeleted := storage.Get().DeleteAllServiceStatusesNotInKeys(keys)
+	if numberOfServiceStatusesDeleted > 0 {
+		log.Printf("[config][validateStorageConfig] Deleted %d service statuses because their matching services no longer existed", numberOfServiceStatusesDeleted)
+	}
+	return nil
+}
+
+func validateWebConfig(config *Config) error {
+	if config.Web == nil {
+		config.Web = &WebConfig{Address: DefaultAddress, Port: DefaultPort}
+	} else {
+		return config.Web.validateAndSetDefaults()
+	}
+	return nil
+}
+
+// deprecated
+// I don't like the current implementation.
+func validateKubernetesConfig(config *Config) error {
+	if config.Kubernetes != nil && config.Kubernetes.AutoDiscover {
+		log.Println("WARNING - The Kubernetes integration is planned to be removed in v3.0.0. If you're seeing this message, it's because you're currently using it, and you may want to give your opinion at https://github.com/TwinProduction/gatus/discussions/135")
+		if config.Kubernetes.ServiceTemplate == nil {
+			return errors.New("kubernetes.service-template cannot be nil")
+		}
+		if config.Debug {
+			log.Println("[config][validateKubernetesConfig] Automatically discovering Kubernetes services...")
+		}
+		discoveredServices, err := k8s.DiscoverServices(config.Kubernetes)
+		if err != nil {
+			return err
+		}
+		config.Services = append(config.Services, discoveredServices...)
+		log.Printf("[config][validateKubernetesConfig] Discovered %d Kubernetes services", len(discoveredServices))
+	}
+	return nil
+}
+
+func validateServicesConfig(config *Config) error {
+	for _, service := range config.Services {
+		if config.Debug {
+			log.Printf("[config][validateServicesConfig] Validating service '%s'", service.Name)
+		}
+		if err := service.ValidateAndSetDefaults(); err != nil {
+			return err
+		}
+	}
+	log.Printf("[config][validateServicesConfig] Validated %d services", len(config.Services))
+	return nil
+}
+
+func validateSecurityConfig(config *Config) error {
+	if config.Security != nil {
+		if config.Security.IsValid() {
+			if config.Debug {
+				log.Printf("[config][validateSecurityConfig] Basic security configuration has been validated")
+			}
+		} else {
+			// If there was an attempt to configure security, then it must mean that some confidential or private
+			// data are exposed. As a result, we'll force a panic because it's better to be safe than sorry.
+			return ErrInvalidSecurityConfig
+		}
+	}
+	return nil
+}
+
+// validateAlertingConfig validates the alerting configuration
+// Note that the alerting configuration has to be validated before the service configuration, because the default alert
+// returned by provider.AlertProvider.GetDefaultAlert() must be parsed before core.Service.ValidateAndSetDefaults()
+// sets the default alert values when none are set.
+func validateAlertingConfig(alertingConfig *alerting.Config, services []*core.Service, debug bool) {
+	if alertingConfig == nil {
+		log.Printf("[config][validateAlertingConfig] Alerting is not configured")
+		return
+	}
+	alertTypes := []alert.Type{
+		alert.TypeCustom,
+		alert.TypeDiscord,
+		alert.TypeMattermost,
+		alert.TypeMessagebird,
+		alert.TypePagerDuty,
+		alert.TypeSlack,
+		alert.TypeTeams,
+		alert.TypeTelegram,
+		alert.TypeTwilio,
+	}
+	var validProviders, invalidProviders []alert.Type
+	for _, alertType := range alertTypes {
+		alertProvider := alertingConfig.GetAlertingProviderByAlertType(alertType)
+		if alertProvider != nil {
+			if alertProvider.IsValid() {
+				// Parse alerts with the provider's default alert
+				if alertProvider.GetDefaultAlert() != nil {
+					for _, service := range services {
+						for alertIndex, serviceAlert := range service.Alerts {
+							if alertType == serviceAlert.Type {
+								if debug {
+									log.Printf("[config][validateAlertingConfig] Parsing alert %d with provider's default alert for provider=%s in service=%s", alertIndex, alertType, service.Name)
+								}
+								provider.ParseWithDefaultAlert(alertProvider.GetDefaultAlert(), serviceAlert)
+							}
+						}
+					}
+				}
+				validProviders = append(validProviders, alertType)
+			} else {
+				log.Printf("[config][validateAlertingConfig] Ignoring provider=%s because configuration is invalid", alertType)
+				invalidProviders = append(invalidProviders, alertType)
+			}
+		} else {
+			invalidProviders = append(invalidProviders, alertType)
+		}
+	}
+	log.Printf("[config][validateAlertingConfig] configuredProviders=%s; ignoredProviders=%s", validProviders, invalidProviders)
+}

config/web.go

@@ -0,0 +1,36 @@
+package config
+
+import (
+	"fmt"
+	"math"
+)
+
+// WebConfig is the structure which supports the configuration of the endpoint
+// which provides access to the web frontend
+type WebConfig struct {
+	// Address to listen on (defaults to 0.0.0.0 specified by DefaultAddress)
+	Address string `yaml:"address"`
+
+	// Port to listen on (default to 8080 specified by DefaultPort)
+	Port int `yaml:"port"`
+}
+
+// validateAndSetDefaults checks and sets the default values for fields that are not set
+func (web *WebConfig) validateAndSetDefaults() error {
+	// Validate the Address
+	if len(web.Address) == 0 {
+		web.Address = DefaultAddress
+	}
+	// Validate the Port
+	if web.Port == 0 {
+		web.Port = DefaultPort
+	} else if web.Port < 0 || web.Port > math.MaxUint16 {
+		return fmt.Errorf("invalid port: value should be between %d and %d", 0, math.MaxUint16)
+	}
+	return nil
+}
+
+// SocketAddress returns the combination of the Address and the Port
+func (web *WebConfig) SocketAddress() string {
+	return fmt.Sprintf("%s:%d", web.Address, web.Port)
+}

config/web_test.go

@@ -0,0 +1,15 @@
+package config
+
+import (
+	"testing"
+)
+
+func TestWebConfig_SocketAddress(t *testing.T) {
+	web := &WebConfig{
+		Address: "0.0.0.0",
+		Port:    8081,
+	}
+	if web.SocketAddress() != "0.0.0.0:8081" {
+		t.Errorf("expected %s, got %s", "0.0.0.0:8081", web.SocketAddress())
+	}
+}

controller/badge.go

@@ -0,0 +1,120 @@
+package controller
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/TwinProduction/gatus/storage"
+	"github.com/TwinProduction/gatus/storage/store/common"
+	"github.com/gorilla/mux"
+)
+
+// badgeHandler handles the automatic generation of badge based on the group name and service name passed.
+//
+// Valid values for {duration}: 7d, 24h, 1h
+// Pattern for {identifier}: <KEY>.svg
+func badgeHandler(writer http.ResponseWriter, request *http.Request) {
+	variables := mux.Vars(request)
+	duration := variables["duration"]
+	var from time.Time
+	switch duration {
+	case "7d":
+		from = time.Now().Add(-time.Hour * 24 * 7)
+	case "24h":
+		from = time.Now().Add(-time.Hour * 24)
+	case "1h":
+		from = time.Now().Add(-time.Hour)
+	default:
+		writer.WriteHeader(http.StatusBadRequest)
+		_, _ = writer.Write([]byte("Durations supported: 7d, 24h, 1h"))
+		return
+	}
+	identifier := variables["identifier"]
+	key := strings.TrimSuffix(identifier, ".svg")
+	uptime, err := storage.Get().GetUptimeByKey(key, from, time.Now())
+	if err != nil {
+		if err == common.ErrServiceNotFound {
+			writer.WriteHeader(http.StatusNotFound)
+		} else if err == common.ErrInvalidTimeRange {
+			writer.WriteHeader(http.StatusBadRequest)
+		} else {
+			writer.WriteHeader(http.StatusInternalServerError)
+		}
+		_, _ = writer.Write([]byte(err.Error()))
+		return
+	}
+	formattedDate := time.Now().Format(http.TimeFormat)
+	writer.Header().Set("Cache-Control", "no-cache, no-store, must-revalidate")
+	writer.Header().Set("Date", formattedDate)
+	writer.Header().Set("Expires", formattedDate)
+	writer.Header().Set("Content-Type", "image/svg+xml")
+	_, _ = writer.Write(generateSVG(duration, uptime))
+}
+
+func generateSVG(duration string, uptime float64) []byte {
+	var labelWidth, valueWidth, valueWidthAdjustment int
+	switch duration {
+	case "7d":
+		labelWidth = 65
+	case "24h":
+		labelWidth = 70
+	case "1h":
+		labelWidth = 65
+	default:
+	}
+	color := getBadgeColorFromUptime(uptime)
+	sanitizedValue := strings.TrimRight(strings.TrimRight(fmt.Sprintf("%.2f", uptime*100), "0"), ".") + "%"
+	if strings.Contains(sanitizedValue, ".") {
+		valueWidthAdjustment = -10
+	}
+	valueWidth = (len(sanitizedValue) * 11) + valueWidthAdjustment
+	width := labelWidth + valueWidth
+	labelX := labelWidth / 2
+	valueX := labelWidth + (valueWidth / 2)
+	svg := []byte(fmt.Sprintf(`<svg xmlns="http://www.w3.org/2000/svg" width="%d" height="20">
+  <linearGradient id="b" x2="0" y2="100%%">
+    <stop offset="0" stop-color="#bbb" stop-opacity=".1"/>
+    <stop offset="1" stop-opacity=".1"/>
+  </linearGradient>
+  <mask id="a">
+    <rect width="%d" height="20" rx="3" fill="#fff"/>
+  </mask>
+  <g mask="url(#a)">
+    <path fill="#555" d="M0 0h%dv20H0z"/>
+    <path fill="%s" d="M%d 0h%dv20H%dz"/>
+    <path fill="url(#b)" d="M0 0h%dv20H0z"/>
+  </g>
+  <g fill="#fff" text-anchor="middle" font-family="DejaVu Sans,Verdana,Geneva,sans-serif" font-size="11">
+    <text x="%d" y="15" fill="#010101" fill-opacity=".3">
+      uptime %s
+    </text>
+    <text x="%d" y="14">
+      uptime %s
+    </text>
+    <text x="%d" y="15" fill="#010101" fill-opacity=".3">
+      %s
+    </text>
+    <text x="%d" y="14">
+      %s
+    </text>
+  </g>
+</svg>`, width, width, labelWidth, color, labelWidth, valueWidth, labelWidth, width, labelX, duration, labelX, duration, valueX, sanitizedValue, valueX, sanitizedValue))
+	return svg
+}
+
+func getBadgeColorFromUptime(uptime float64) string {
+	if uptime >= 0.975 {
+		return "#40cc11"
+	} else if uptime >= 0.95 {
+		return "#94cc11"
+	} else if uptime >= 0.9 {
+		return "#ccc311"
+	} else if uptime >= 0.8 {
+		return "#ccb311"
+	} else if uptime >= 0.5 {
+		return "#cc8111"
+	}
+	return "#c7130a"
+}

controller/badge_test.go

@@ -0,0 +1,32 @@
+package controller
+
+import (
+	"testing"
+)
+
+func TestGetBadgeColorFromUptime(t *testing.T) {
+	if getBadgeColorFromUptime(1) != "#40cc11" {
+		t.Error("expected #40cc11 from an uptime of 1, got", getBadgeColorFromUptime(1))
+	}
+	if getBadgeColorFromUptime(0.95) != "#94cc11" {
+		t.Error("expected #94cc11 from an uptime of 0.95, got", getBadgeColorFromUptime(0.95))
+	}
+	if getBadgeColorFromUptime(0.9) != "#ccc311" {
+		t.Error("expected #c9cc11 from an uptime of 0.9, got", getBadgeColorFromUptime(0.9))
+	}
+	if getBadgeColorFromUptime(0.85) != "#ccb311" {
+		t.Error("expected #ccb311 from an uptime of 0.85, got", getBadgeColorFromUptime(0.85))
+	}
+	if getBadgeColorFromUptime(0.75) != "#cc8111" {
+		t.Error("expected #cc8111 from an uptime of 0.75, got", getBadgeColorFromUptime(0.75))
+	}
+	if getBadgeColorFromUptime(0.6) != "#cc8111" {
+		t.Error("expected #cc8111 from an uptime of 0.6, got", getBadgeColorFromUptime(0.6))
+	}
+	if getBadgeColorFromUptime(0.25) != "#c7130a" {
+		t.Error("expected #c7130a from an uptime of 0.25, got", getBadgeColorFromUptime(0.25))
+	}
+	if getBadgeColorFromUptime(0) != "#c7130a" {
+		t.Error("expected #c7130a from an uptime of 0, got", getBadgeColorFromUptime(0))
+	}
+}

controller/controller.go

@@ -0,0 +1,174 @@
+package controller
+
+import (
+	"bytes"
+	"compress/gzip"
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/TwinProduction/gatus/config"
+	"github.com/TwinProduction/gatus/security"
+	"github.com/TwinProduction/gatus/storage"
+	"github.com/TwinProduction/gatus/storage/store/common"
+	"github.com/TwinProduction/gatus/storage/store/common/paging"
+	"github.com/TwinProduction/gocache"
+	"github.com/TwinProduction/health"
+	"github.com/gorilla/mux"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+const (
+	cacheTTL = 10 * time.Second
+)
+
+var (
+	cache = gocache.NewCache().WithMaxSize(100).WithEvictionPolicy(gocache.FirstInFirstOut)
+
+	// staticFolder is the path to the location of the static folder from the root path of the project
+	// The only reason this is exposed is to allow running tests from a different path than the root path of the project
+	staticFolder = "./web/static"
+
+	// server is the http.Server created by Handle.
+	// The only reason it exists is for testing purposes.
+	server *http.Server
+)
+
+// Handle creates the router and starts the server
+func Handle(securityConfig *security.Config, webConfig *config.WebConfig, enableMetrics bool) {
+	var router http.Handler = CreateRouter(securityConfig, enableMetrics)
+	if os.Getenv("ENVIRONMENT") == "dev" {
+		router = developmentCorsHandler(router)
+	}
+	server = &http.Server{
+		Addr:         fmt.Sprintf("%s:%d", webConfig.Address, webConfig.Port),
+		Handler:      router,
+		ReadTimeout:  15 * time.Second,
+		WriteTimeout: 15 * time.Second,
+		IdleTimeout:  15 * time.Second,
+	}
+	log.Println("[controller][Handle] Listening on " + webConfig.SocketAddress())
+	if os.Getenv("ROUTER_TEST") == "true" {
+		return
+	}
+	log.Println("[controller][Handle]", server.ListenAndServe())
+}
+
+// Shutdown stops the server
+func Shutdown() {
+	if server != nil {
+		_ = server.Shutdown(context.TODO())
+		server = nil
+	}
+}
+
+// CreateRouter creates the router for the http server
+func CreateRouter(securityConfig *security.Config, enabledMetrics bool) *mux.Router {
+	router := mux.NewRouter()
+	if enabledMetrics {
+		router.Handle("/metrics", promhttp.Handler()).Methods("GET")
+	}
+	router.Handle("/health", health.Handler().WithJSON(true)).Methods("GET")
+	router.HandleFunc("/favicon.ico", favIconHandler).Methods("GET")
+	router.HandleFunc("/api/v1/statuses", secureIfNecessary(securityConfig, serviceStatusesHandler)).Methods("GET") // No GzipHandler for this one, because we cache the content
+	router.HandleFunc("/api/v1/statuses/{key}", secureIfNecessary(securityConfig, GzipHandlerFunc(serviceStatusHandler))).Methods("GET")
+	router.HandleFunc("/api/v1/badges/uptime/{duration}/{identifier}", badgeHandler).Methods("GET")
+	// SPA
+	router.HandleFunc("/services/{service}", spaHandler).Methods("GET")
+	// Everything else falls back on static content
+	router.PathPrefix("/").Handler(GzipHandler(http.FileServer(http.Dir(staticFolder))))
+	return router
+}
+
+func secureIfNecessary(securityConfig *security.Config, handler http.HandlerFunc) http.HandlerFunc {
+	if securityConfig != nil && securityConfig.IsValid() {
+		return security.Handler(handler, securityConfig)
+	}
+	return handler
+}
+
+// serviceStatusesHandler handles requests to retrieve all service statuses
+// Due to the size of the response, this function leverages a cache.
+// Must not be wrapped by GzipHandler
+func serviceStatusesHandler(writer http.ResponseWriter, r *http.Request) {
+	page, pageSize := extractPageAndPageSizeFromRequest(r)
+	gzipped := strings.Contains(r.Header.Get("Accept-Encoding"), "gzip")
+	var exists bool
+	var value interface{}
+	if gzipped {
+		writer.Header().Set("Content-Encoding", "gzip")
+		value, exists = cache.Get(fmt.Sprintf("service-status-%d-%d-gzipped", page, pageSize))
+	} else {
+		value, exists = cache.Get(fmt.Sprintf("service-status-%d-%d", page, pageSize))
+	}
+	var data []byte
+	if !exists {
+		var err error
+		buffer := &bytes.Buffer{}
+		gzipWriter := gzip.NewWriter(buffer)
+		data, err = json.Marshal(storage.Get().GetAllServiceStatuses(paging.NewServiceStatusParams().WithResults(page, pageSize)))
+		if err != nil {
+			log.Printf("[controller][serviceStatusesHandler] Unable to marshal object to JSON: %s", err.Error())
+			writer.WriteHeader(http.StatusInternalServerError)
+			_, _ = writer.Write([]byte("Unable to marshal object to JSON"))
+			return
+		}
+		_, _ = gzipWriter.Write(data)
+		_ = gzipWriter.Close()
+		gzippedData := buffer.Bytes()
+		cache.SetWithTTL(fmt.Sprintf("service-status-%d-%d", page, pageSize), data, cacheTTL)
+		cache.SetWithTTL(fmt.Sprintf("service-status-%d-%d-gzipped", page, pageSize), gzippedData, cacheTTL)
+		if gzipped {
+			data = gzippedData
+		}
+	} else {
+		data = value.([]byte)
+	}
+	writer.Header().Add("Content-Type", "application/json")
+	writer.WriteHeader(http.StatusOK)
+	_, _ = writer.Write(data)
+}
+
+// serviceStatusHandler retrieves a single ServiceStatus by group name and service name
+func serviceStatusHandler(writer http.ResponseWriter, r *http.Request) {
+	page, pageSize := extractPageAndPageSizeFromRequest(r)
+	vars := mux.Vars(r)
+	serviceStatus := storage.Get().GetServiceStatusByKey(vars["key"], paging.NewServiceStatusParams().WithResults(page, pageSize).WithEvents(1, common.MaximumNumberOfEvents))
+	if serviceStatus == nil {
+		log.Printf("[controller][serviceStatusHandler] Service with key=%s not found", vars["key"])
+		writer.WriteHeader(http.StatusNotFound)
+		_, _ = writer.Write([]byte("not found"))
+		return
+	}
+	uptime7Days, _ := storage.Get().GetUptimeByKey(vars["key"], time.Now().Add(-time.Hour*24*7), time.Now())
+	uptime24Hours, _ := storage.Get().GetUptimeByKey(vars["key"], time.Now().Add(-time.Hour*24), time.Now())
+	uptime1Hour, _ := storage.Get().GetUptimeByKey(vars["key"], time.Now().Add(-time.Hour), time.Now())
+	data := map[string]interface{}{
+		"serviceStatus": serviceStatus,
+		// The following fields, while present on core.ServiceStatus, are annotated to remain hidden so that we can
+		// expose only the necessary data on /api/v1/statuses.
+		// Since the /api/v1/statuses/{key} endpoint does need this data, however, we explicitly expose it here
+		"events": serviceStatus.Events,
+		// TODO: remove this in v3.0.0. Not used by front-end, only used for API. Left here for v2.x.x backward compatibility
+		"uptime": map[string]float64{
+			"7d":  uptime7Days,
+			"24h": uptime24Hours,
+			"1h":  uptime1Hour,
+		},
+	}
+	output, err := json.Marshal(data)
+	if err != nil {
+		log.Printf("[controller][serviceStatusHandler] Unable to marshal object to JSON: %s", err.Error())
+		writer.WriteHeader(http.StatusInternalServerError)
+		_, _ = writer.Write([]byte("unable to marshal object to JSON"))
+		return
+	}
+	writer.Header().Add("Content-Type", "application/json")
+	writer.WriteHeader(http.StatusOK)
+	_, _ = writer.Write(output)
+}

controller/controller_test.go

@@ -0,0 +1,328 @@
+package controller
+
+import (
+	"math/rand"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/TwinProduction/gatus/config"
+	"github.com/TwinProduction/gatus/core"
+	"github.com/TwinProduction/gatus/storage"
+	"github.com/TwinProduction/gatus/watchdog"
+)
+
+var (
+	firstCondition  = core.Condition("[STATUS] == 200")
+	secondCondition = core.Condition("[RESPONSE_TIME] < 500")
+	thirdCondition  = core.Condition("[CERTIFICATE_EXPIRATION] < 72h")
+
+	timestamp = time.Now()
+
+	testService = core.Service{
+		Name:                    "name",
+		Group:                   "group",
+		URL:                     "https://example.org/what/ever",
+		Method:                  "GET",
+		Body:                    "body",
+		Interval:                30 * time.Second,
+		Conditions:              []*core.Condition{&firstCondition, &secondCondition, &thirdCondition},
+		Alerts:                  nil,
+		NumberOfFailuresInARow:  0,
+		NumberOfSuccessesInARow: 0,
+	}
+	testSuccessfulResult = core.Result{
+		Hostname:              "example.org",
+		IP:                    "127.0.0.1",
+		HTTPStatus:            200,
+		Errors:                nil,
+		Connected:             true,
+		Success:               true,
+		Timestamp:             timestamp,
+		Duration:              150 * time.Millisecond,
+		CertificateExpiration: 10 * time.Hour,
+		ConditionResults: []*core.ConditionResult{
+			{
+				Condition: "[STATUS] == 200",
+				Success:   true,
+			},
+			{
+				Condition: "[RESPONSE_TIME] < 500",
+				Success:   true,
+			},
+			{
+				Condition: "[CERTIFICATE_EXPIRATION] < 72h",
+				Success:   true,
+			},
+		},
+	}
+	testUnsuccessfulResult = core.Result{
+		Hostname:              "example.org",
+		IP:                    "127.0.0.1",
+		HTTPStatus:            200,
+		Errors:                []string{"error-1", "error-2"},
+		Connected:             true,
+		Success:               false,
+		Timestamp:             timestamp,
+		Duration:              750 * time.Millisecond,
+		CertificateExpiration: 10 * time.Hour,
+		ConditionResults: []*core.ConditionResult{
+			{
+				Condition: "[STATUS] == 200",
+				Success:   true,
+			},
+			{
+				Condition: "[RESPONSE_TIME] < 500",
+				Success:   false,
+			},
+			{
+				Condition: "[CERTIFICATE_EXPIRATION] < 72h",
+				Success:   false,
+			},
+		},
+	}
+)
+
+func TestCreateRouter(t *testing.T) {
+	defer storage.Get().Clear()
+	defer cache.Clear()
+	staticFolder = "../web/static"
+	cfg := &config.Config{
+		Metrics: true,
+		Services: []*core.Service{
+			{
+				Name:  "frontend",
+				Group: "core",
+			},
+			{
+				Name:  "backend",
+				Group: "core",
+			},
+		},
+	}
+	watchdog.UpdateServiceStatuses(cfg.Services[0], &core.Result{Success: true, Duration: time.Millisecond, Timestamp: time.Now()})
+	watchdog.UpdateServiceStatuses(cfg.Services[1], &core.Result{Success: false, Duration: time.Second, Timestamp: time.Now()})
+	router := CreateRouter(cfg.Security, cfg.Metrics)
+	type Scenario struct {
+		Name         string
+		Path         string
+		ExpectedCode int
+		Gzip         bool
+	}
+	scenarios := []Scenario{
+		{
+			Name:         "health",
+			Path:         "/health",
+			ExpectedCode: http.StatusOK,
+		},
+		{
+			Name:         "metrics",
+			Path:         "/metrics",
+			ExpectedCode: http.StatusOK,
+		},
+		{
+			Name:         "badges-1h",
+			Path:         "/api/v1/badges/uptime/1h/core_frontend.svg",
+			ExpectedCode: http.StatusOK,
+		},
+		{
+			Name:         "badges-24h",
+			Path:         "/api/v1/badges/uptime/24h/core_backend.svg",
+			ExpectedCode: http.StatusOK,
+		},
+		{
+			Name:         "badges-7d",
+			Path:         "/api/v1/badges/uptime/7d/core_frontend.svg",
+			ExpectedCode: http.StatusOK,
+		},
+		{
+			Name:         "badges-with-invalid-duration",
+			Path:         "/api/v1/badges/uptime/3d/core_backend.svg",
+			ExpectedCode: http.StatusBadRequest,
+		},
+		{
+			Name:         "badges-for-invalid-key",
+			Path:         "/api/v1/badges/uptime/7d/invalid_key.svg",
+			ExpectedCode: http.StatusNotFound,
+		},
+		{
+			Name:         "service-statuses",
+			Path:         "/api/v1/statuses",
+			ExpectedCode: http.StatusOK,
+		},
+		{
+			Name:         "service-statuses-gzip",
+			Path:         "/api/v1/statuses",
+			ExpectedCode: http.StatusOK,
+			Gzip:         true,
+		},
+		{
+			Name:         "service-statuses-pagination",
+			Path:         "/api/v1/statuses?page=1&pageSize=20",
+			ExpectedCode: http.StatusOK,
+		},
+		{
+			Name:         "service-status",
+			Path:         "/api/v1/statuses/core_frontend",
+			ExpectedCode: http.StatusOK,
+		},
+		{
+			Name:         "service-status-gzip",
+			Path:         "/api/v1/statuses/core_frontend",
+			ExpectedCode: http.StatusOK,
+			Gzip:         true,
+		},
+		{
+			Name:         "service-status-for-invalid-key",
+			Path:         "/api/v1/statuses/invalid_key",
+			ExpectedCode: http.StatusNotFound,
+		},
+		{
+			Name:         "favicon",
+			Path:         "/favicon.ico",
+			ExpectedCode: http.StatusOK,
+		},
+		{
+			Name:         "frontend-home",
+			Path:         "/",
+			ExpectedCode: http.StatusOK,
+		},
+		{
+			Name:         "frontend-assets",
+			Path:         "/js/app.js",
+			ExpectedCode: http.StatusOK,
+		},
+		{
+			Name:         "frontend-service",
+			Path:         "/services/core_frontend",
+			ExpectedCode: http.StatusOK,
+		},
+	}
+	for _, scenario := range scenarios {
+		t.Run(scenario.Name, func(t *testing.T) {
+			request, _ := http.NewRequest("GET", scenario.Path, nil)
+			if scenario.Gzip {
+				request.Header.Set("Accept-Encoding", "gzip")
+			}
+			responseRecorder := httptest.NewRecorder()
+			router.ServeHTTP(responseRecorder, request)
+			if responseRecorder.Code != scenario.ExpectedCode {
+				t.Errorf("%s %s should have returned %d, but returned %d instead", request.Method, request.URL, scenario.ExpectedCode, responseRecorder.Code)
+			}
+		})
+	}
+}
+
+func TestHandle(t *testing.T) {
+	defer storage.Get().Clear()
+	defer cache.Clear()
+	cfg := &config.Config{
+		Web: &config.WebConfig{
+			Address: "0.0.0.0",
+			Port:    rand.Intn(65534),
+		},
+		Services: []*core.Service{
+			{
+				Name:  "frontend",
+				Group: "core",
+			},
+			{
+				Name:  "backend",
+				Group: "core",
+			},
+		},
+	}
+	_ = os.Setenv("ROUTER_TEST", "true")
+	_ = os.Setenv("ENVIRONMENT", "dev")
+	defer os.Clearenv()
+	Handle(cfg.Security, cfg.Web, cfg.Metrics)
+	defer Shutdown()
+	request, _ := http.NewRequest("GET", "/health", nil)
+	responseRecorder := httptest.NewRecorder()
+	server.Handler.ServeHTTP(responseRecorder, request)
+	if responseRecorder.Code != http.StatusOK {
+		t.Error("expected GET /health to return status code 200")
+	}
+	if server == nil {
+		t.Fatal("server should've been set (but because we set ROUTER_TEST, it shouldn't have been started)")
+	}
+}
+
+func TestShutdown(t *testing.T) {
+	// Pretend that we called controller.Handle(), which initializes the server variable
+	server = &http.Server{}
+	Shutdown()
+	if server != nil {
+		t.Error("server should've been shut down")
+	}
+}
+
+func TestServiceStatusesHandler(t *testing.T) {
+	defer storage.Get().Clear()
+	defer cache.Clear()
+	staticFolder = "../web/static"
+	firstResult := &testSuccessfulResult
+	secondResult := &testUnsuccessfulResult
+	storage.Get().Insert(&testService, firstResult)
+	storage.Get().Insert(&testService, secondResult)
+	// Can't be bothered dealing with timezone issues on the worker that runs the automated tests
+	firstResult.Timestamp = time.Time{}
+	secondResult.Timestamp = time.Time{}
+	router := CreateRouter(nil, false)
+
+	type Scenario struct {
+		Name         string
+		Path         string
+		ExpectedCode int
+		ExpectedBody string
+	}
+	scenarios := []Scenario{
+		{
+			Name:         "no-pagination",
+			Path:         "/api/v1/statuses",
+			ExpectedCode: http.StatusOK,
+			ExpectedBody: `{"group_name":{"name":"name","group":"group","key":"group_name","results":[{"status":200,"hostname":"example.org","duration":150000000,"errors":null,"conditionResults":[{"condition":"[STATUS] == 200","success":true},{"condition":"[RESPONSE_TIME] \u003c 500","success":true},{"condition":"[CERTIFICATE_EXPIRATION] \u003c 72h","success":true}],"success":true,"timestamp":"0001-01-01T00:00:00Z"},{"status":200,"hostname":"example.org","duration":750000000,"errors":["error-1","error-2"],"conditionResults":[{"condition":"[STATUS] == 200","success":true},{"condition":"[RESPONSE_TIME] \u003c 500","success":false},{"condition":"[CERTIFICATE_EXPIRATION] \u003c 72h","success":false}],"success":false,"timestamp":"0001-01-01T00:00:00Z"}]}}`,
+		},
+		{
+			Name:         "pagination-first-result",
+			Path:         "/api/v1/statuses?page=1&pageSize=1",
+			ExpectedCode: http.StatusOK,
+			ExpectedBody: `{"group_name":{"name":"name","group":"group","key":"group_name","results":[{"status":200,"hostname":"example.org","duration":750000000,"errors":["error-1","error-2"],"conditionResults":[{"condition":"[STATUS] == 200","success":true},{"condition":"[RESPONSE_TIME] \u003c 500","success":false},{"condition":"[CERTIFICATE_EXPIRATION] \u003c 72h","success":false}],"success":false,"timestamp":"0001-01-01T00:00:00Z"}]}}`,
+		},
+		{
+			Name:         "pagination-second-result",
+			Path:         "/api/v1/statuses?page=2&pageSize=1",
+			ExpectedCode: http.StatusOK,
+			ExpectedBody: `{"group_name":{"name":"name","group":"group","key":"group_name","results":[{"status":200,"hostname":"example.org","duration":150000000,"errors":null,"conditionResults":[{"condition":"[STATUS] == 200","success":true},{"condition":"[RESPONSE_TIME] \u003c 500","success":true},{"condition":"[CERTIFICATE_EXPIRATION] \u003c 72h","success":true}],"success":true,"timestamp":"0001-01-01T00:00:00Z"}]}}`,
+		},
+		{
+			Name:         "pagination-no-results",
+			Path:         "/api/v1/statuses?page=5&pageSize=20",
+			ExpectedCode: http.StatusOK,
+			ExpectedBody: `{"group_name":{"name":"name","group":"group","key":"group_name","results":[]}}`,
+		},
+		{
+			Name:         "invalid-pagination-should-fall-back-to-default",
+			Path:         "/api/v1/statuses?page=INVALID&pageSize=INVALID",
+			ExpectedCode: http.StatusOK,
+			ExpectedBody: `{"group_name":{"name":"name","group":"group","key":"group_name","results":[{"status":200,"hostname":"example.org","duration":150000000,"errors":null,"conditionResults":[{"condition":"[STATUS] == 200","success":true},{"condition":"[RESPONSE_TIME] \u003c 500","success":true},{"condition":"[CERTIFICATE_EXPIRATION] \u003c 72h","success":true}],"success":true,"timestamp":"0001-01-01T00:00:00Z"},{"status":200,"hostname":"example.org","duration":750000000,"errors":["error-1","error-2"],"conditionResults":[{"condition":"[STATUS] == 200","success":true},{"condition":"[RESPONSE_TIME] \u003c 500","success":false},{"condition":"[CERTIFICATE_EXPIRATION] \u003c 72h","success":false}],"success":false,"timestamp":"0001-01-01T00:00:00Z"}]}}`,
+		},
+	}
+
+	for _, scenario := range scenarios {
+		t.Run(scenario.Name, func(t *testing.T) {
+			request, _ := http.NewRequest("GET", scenario.Path, nil)
+			responseRecorder := httptest.NewRecorder()
+			router.ServeHTTP(responseRecorder, request)
+			if responseRecorder.Code != scenario.ExpectedCode {
+				t.Errorf("%s %s should have returned %d, but returned %d instead", request.Method, request.URL, scenario.ExpectedCode, responseRecorder.Code)
+			}
+			output := responseRecorder.Body.String()
+			if output != scenario.ExpectedBody {
+				t.Errorf("expected:\n %s\n\ngot:\n %s", scenario.ExpectedBody, output)
+			}
+		})
+	}
+}

controller/cors.go

@@ -0,0 +1,10 @@
+package controller
+
+import "net/http"
+
+func developmentCorsHandler(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Access-Control-Allow-Origin", "http://localhost:8081")
+		next.ServeHTTP(w, r)
+	})
+}

controller/favicon.go

@@ -0,0 +1,8 @@
+package controller
+
+import "net/http"
+
+// favIconHandler handles requests for /favicon.ico
+func favIconHandler(writer http.ResponseWriter, request *http.Request) {
+	http.ServeFile(writer, request, staticFolder+"/favicon.ico")
+}

controller/gzip.go

@@ -0,0 +1,59 @@
+package controller
+
+import (
+	"compress/gzip"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"strings"
+	"sync"
+)
+
+var gzPool = sync.Pool{
+	New: func() interface{} {
+		return gzip.NewWriter(ioutil.Discard)
+	},
+}
+
+type gzipResponseWriter struct {
+	io.Writer
+	http.ResponseWriter
+}
+
+// WriteHeader sends an HTTP response header with the provided status code.
+// It also deletes the Content-Length header, since the GZIP compression may modify the size of the payload
+func (w *gzipResponseWriter) WriteHeader(status int) {
+	w.Header().Del("Content-Length")
+	w.ResponseWriter.WriteHeader(status)
+}
+
+// Write writes len(b) bytes from b to the underlying data stream.
+func (w *gzipResponseWriter) Write(b []byte) (int, error) {
+	return w.Writer.Write(b)
+}
+
+// GzipHandler compresses the response of a given http.Handler if the request's headers specify that the client
+// supports gzip encoding
+func GzipHandler(next http.Handler) http.Handler {
+	return GzipHandlerFunc(func(writer http.ResponseWriter, r *http.Request) {
+		next.ServeHTTP(writer, r)
+	})
+}
+
+// GzipHandlerFunc compresses the response of a given http.HandlerFunc if the request's headers specify that the client
+// supports gzip encoding
+func GzipHandlerFunc(next http.HandlerFunc) http.HandlerFunc {
+	return func(writer http.ResponseWriter, r *http.Request) {
+		// If the request doesn't specify that it supports gzip, then don't compress it
+		if !strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
+			next.ServeHTTP(writer, r)
+			return
+		}
+		writer.Header().Set("Content-Encoding", "gzip")
+		gz := gzPool.Get().(*gzip.Writer)
+		defer gzPool.Put(gz)
+		gz.Reset(writer)
+		defer gz.Close()
+		next.ServeHTTP(&gzipResponseWriter{ResponseWriter: writer, Writer: gz}, r)
+	}
+}

controller/spa.go

@@ -0,0 +1,8 @@
+package controller
+
+import "net/http"
+
+// spaHandler handles requests for /
+func spaHandler(writer http.ResponseWriter, request *http.Request) {
+	http.ServeFile(writer, request, staticFolder+"/index.html")
+}

controller/util.go

@@ -0,0 +1,48 @@
+package controller
+
+import (
+	"net/http"
+	"strconv"
+
+	"github.com/TwinProduction/gatus/storage/store/common"
+)
+
+const (
+	// DefaultPage is the default page to use if none is specified or an invalid value is provided
+	DefaultPage = 1
+
+	// DefaultPageSize is the default page siZE to use if none is specified or an invalid value is provided
+	DefaultPageSize = 20
+
+	// MaximumPageSize is the maximum page size allowed
+	MaximumPageSize = common.MaximumNumberOfResults
+)
+
+func extractPageAndPageSizeFromRequest(r *http.Request) (page int, pageSize int) {
+	var err error
+	if pageParameter := r.URL.Query().Get("page"); len(pageParameter) == 0 {
+		page = DefaultPage
+	} else {
+		page, err = strconv.Atoi(pageParameter)
+		if err != nil {
+			page = DefaultPage
+		}
+		if page < 1 {
+			page = DefaultPage
+		}
+	}
+	if pageSizeParameter := r.URL.Query().Get("pageSize"); len(pageSizeParameter) == 0 {
+		pageSize = DefaultPageSize
+	} else {
+		pageSize, err = strconv.Atoi(pageSizeParameter)
+		if err != nil {
+			pageSize = DefaultPageSize
+		}
+		if pageSize > MaximumPageSize {
+			pageSize = MaximumPageSize
+		} else if pageSize < 1 {
+			pageSize = DefaultPageSize
+		}
+	}
+	return
+}

controller/util_test.go

@@ -0,0 +1,67 @@
+package controller
+
+import (
+	"fmt"
+	"net/http"
+	"testing"
+)
+
+func TestExtractPageAndPageSizeFromRequest(t *testing.T) {
+	type Scenario struct {
+		Name             string
+		Page             string
+		PageSize         string
+		ExpectedPage     int
+		ExpectedPageSize int
+	}
+	scenarios := []Scenario{
+		{
+			Page:             "1",
+			PageSize:         "20",
+			ExpectedPage:     1,
+			ExpectedPageSize: 20,
+		},
+		{
+			Page:             "2",
+			PageSize:         "10",
+			ExpectedPage:     2,
+			ExpectedPageSize: 10,
+		},
+		{
+			Page:             "2",
+			PageSize:         "10",
+			ExpectedPage:     2,
+			ExpectedPageSize: 10,
+		},
+		{
+			Page:             "1",
+			PageSize:         "999999",
+			ExpectedPage:     1,
+			ExpectedPageSize: MaximumPageSize,
+		},
+		{
+			Page:             "-1",
+			PageSize:         "-1",
+			ExpectedPage:     DefaultPage,
+			ExpectedPageSize: DefaultPageSize,
+		},
+		{
+			Page:             "invalid",
+			PageSize:         "invalid",
+			ExpectedPage:     DefaultPage,
+			ExpectedPageSize: DefaultPageSize,
+		},
+	}
+	for _, scenario := range scenarios {
+		t.Run("page-"+scenario.Page+"-pageSize-"+scenario.PageSize, func(t *testing.T) {
+			request, _ := http.NewRequest("GET", fmt.Sprintf("/api/v1/statuses?page=%s&pageSize=%s", scenario.Page, scenario.PageSize), nil)
+			actualPage, actualPageSize := extractPageAndPageSizeFromRequest(request)
+			if actualPage != scenario.ExpectedPage {
+				t.Errorf("expected %d, got %d", scenario.ExpectedPage, actualPage)
+			}
+			if actualPageSize != scenario.ExpectedPageSize {
+				t.Errorf("expected %d, got %d", scenario.ExpectedPageSize, actualPageSize)
+			}
+		})
+	}
+}

core/condition.go

@@ -0,0 +1,314 @@
+package core
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/TwinProduction/gatus/jsonpath"
+	"github.com/TwinProduction/gatus/pattern"
+)
+
+const (
+	// StatusPlaceholder is a placeholder for a HTTP status.
+	//
+	// Values that could replace the placeholder: 200, 404, 500, ...
+	StatusPlaceholder = "[STATUS]"
+
+	// IPPlaceholder is a placeholder for an IP.
+	//
+	// Values that could replace the placeholder: 127.0.0.1, 10.0.0.1, ...
+	IPPlaceholder = "[IP]"
+
+	// DNSRCodePlaceholder is a place holder for DNS_RCODE
+	//
+	// Values that could replace the placeholder: NOERROR, FORMERR, SERVFAIL, NXDOMAIN, NOTIMP, REFUSED
+	DNSRCodePlaceholder = "[DNS_RCODE]"
+
+	// ResponseTimePlaceholder is a placeholder for the request response time, in milliseconds.
+	//
+	// Values that could replace the placeholder: 1, 500, 1000, ...
+	ResponseTimePlaceholder = "[RESPONSE_TIME]"
+
+	// BodyPlaceholder is a placeholder for the body of the response
+	//
+	// Values that could replace the placeholder: {}, {"data":{"name":"john"}}, ...
+	BodyPlaceholder = "[BODY]"
+
+	// ConnectedPlaceholder is a placeholder for whether a connection was successfully established.
+	//
+	// Values that could replace the placeholder: true, false
+	ConnectedPlaceholder = "[CONNECTED]"
+
+	// CertificateExpirationPlaceholder is a placeholder for the duration before certificate expiration, in milliseconds.
+	//
+	// Values that could replace the placeholder: 4461677039 (~52 days)
+	CertificateExpirationPlaceholder = "[CERTIFICATE_EXPIRATION]"
+
+	// LengthFunctionPrefix is the prefix for the length function
+	//
+	// Usage: len([BODY].articles) == 10, len([BODY].name) > 5
+	LengthFunctionPrefix = "len("
+
+	// HasFunctionPrefix is the prefix for the has function
+	//
+	// Usage: has([BODY].errors) == true
+	HasFunctionPrefix = "has("
+
+	// PatternFunctionPrefix is the prefix for the pattern function
+	//
+	// Usage: [IP] == pat(192.168.*.*)
+	PatternFunctionPrefix = "pat("
+
+	// AnyFunctionPrefix is the prefix for the any function
+	//
+	// Usage: [IP] == any(1.1.1.1, 1.0.0.1)
+	AnyFunctionPrefix = "any("
+
+	// FunctionSuffix is the suffix for all functions
+	FunctionSuffix = ")"
+
+	// InvalidConditionElementSuffix is the suffix that will be appended to an invalid condition
+	InvalidConditionElementSuffix = "(INVALID)"
+
+	// maximumLengthBeforeTruncatingWhenComparedWithPattern is the maximum length an element being compared to a
+	// pattern can have.
+	//
+	// This is only used for aesthetic purposes; it does not influence whether the condition evaluation results in a
+	// success or a failure
+	maximumLengthBeforeTruncatingWhenComparedWithPattern = 25
+)
+
+// Condition is a condition that needs to be met in order for a Service to be considered healthy.
+type Condition string
+
+// evaluate the Condition with the Result of the health check
+// TODO: Add a mandatory space between each operators (e.g. " == " instead of "==") (BREAKING CHANGE)
+func (c Condition) evaluate(result *Result) bool {
+	condition := string(c)
+	success := false
+	conditionToDisplay := condition
+	if strings.Contains(condition, "==") {
+		parameters, resolvedParameters := sanitizeAndResolve(strings.Split(condition, "=="), result)
+		success = isEqual(resolvedParameters[0], resolvedParameters[1])
+		if !success {
+			conditionToDisplay = prettify(parameters, resolvedParameters, "==")
+		}
+	} else if strings.Contains(condition, "!=") {
+		parameters, resolvedParameters := sanitizeAndResolve(strings.Split(condition, "!="), result)
+		success = !isEqual(resolvedParameters[0], resolvedParameters[1])
+		if !success {
+			conditionToDisplay = prettify(parameters, resolvedParameters, "!=")
+		}
+	} else if strings.Contains(condition, "<=") {
+		parameters, resolvedParameters := sanitizeAndResolveNumerical(strings.Split(condition, "<="), result)
+		success = resolvedParameters[0] <= resolvedParameters[1]
+		if !success {
+			conditionToDisplay = prettifyNumericalParameters(parameters, resolvedParameters, "<=")
+		}
+	} else if strings.Contains(condition, ">=") {
+		parameters, resolvedParameters := sanitizeAndResolveNumerical(strings.Split(condition, ">="), result)
+		success = resolvedParameters[0] >= resolvedParameters[1]
+		if !success {
+			conditionToDisplay = prettifyNumericalParameters(parameters, resolvedParameters, ">=")
+		}
+	} else if strings.Contains(condition, ">") {
+		parameters, resolvedParameters := sanitizeAndResolveNumerical(strings.Split(condition, ">"), result)
+		success = resolvedParameters[0] > resolvedParameters[1]
+		if !success {
+			conditionToDisplay = prettifyNumericalParameters(parameters, resolvedParameters, ">")
+		}
+	} else if strings.Contains(condition, "<") {
+		parameters, resolvedParameters := sanitizeAndResolveNumerical(strings.Split(condition, "<"), result)
+		success = resolvedParameters[0] < resolvedParameters[1]
+		if !success {
+			conditionToDisplay = prettifyNumericalParameters(parameters, resolvedParameters, "<")
+		}
+	} else {
+		result.AddError(fmt.Sprintf("invalid condition '%s' has been provided", condition))
+		return false
+	}
+	if !success {
+		//log.Printf("[Condition][evaluate] Condition '%s' did not succeed because '%s' is false", condition, condition)
+	}
+	result.ConditionResults = append(result.ConditionResults, &ConditionResult{Condition: conditionToDisplay, Success: success})
+	return success
+}
+
+// hasBodyPlaceholder checks whether the condition has a BodyPlaceholder
+// Used for determining whether the response body should be read or not
+func (c Condition) hasBodyPlaceholder() bool {
+	return strings.Contains(string(c), BodyPlaceholder)
+}
+
+// isEqual compares two strings.
+//
+// Supports the pattern and the any functions.
+// i.e. if one of the parameters starts with PatternFunctionPrefix and ends with FunctionSuffix, it will be treated like
+// a pattern.
+func isEqual(first, second string) bool {
+	firstHasFunctionSuffix := strings.HasSuffix(first, FunctionSuffix)
+	secondHasFunctionSuffix := strings.HasSuffix(second, FunctionSuffix)
+	if firstHasFunctionSuffix || secondHasFunctionSuffix {
+		var isFirstPattern, isSecondPattern bool
+		if strings.HasPrefix(first, PatternFunctionPrefix) && firstHasFunctionSuffix {
+			isFirstPattern = true
+			first = strings.TrimSuffix(strings.TrimPrefix(first, PatternFunctionPrefix), FunctionSuffix)
+		}
+		if strings.HasPrefix(second, PatternFunctionPrefix) && secondHasFunctionSuffix {
+			isSecondPattern = true
+			second = strings.TrimSuffix(strings.TrimPrefix(second, PatternFunctionPrefix), FunctionSuffix)
+		}
+		if isFirstPattern && !isSecondPattern {
+			return pattern.Match(first, second)
+		} else if !isFirstPattern && isSecondPattern {
+			return pattern.Match(second, first)
+		}
+		var isFirstAny, isSecondAny bool
+		if strings.HasPrefix(first, AnyFunctionPrefix) && firstHasFunctionSuffix {
+			isFirstAny = true
+			first = strings.TrimSuffix(strings.TrimPrefix(first, AnyFunctionPrefix), FunctionSuffix)
+		}
+		if strings.HasPrefix(second, AnyFunctionPrefix) && secondHasFunctionSuffix {
+			isSecondAny = true
+			second = strings.TrimSuffix(strings.TrimPrefix(second, AnyFunctionPrefix), FunctionSuffix)
+		}
+		if isFirstAny && !isSecondAny {
+			options := strings.Split(first, ",")
+			for _, option := range options {
+				if strings.TrimSpace(option) == second {
+					return true
+				}
+			}
+			return false
+		} else if !isFirstAny && isSecondAny {
+			options := strings.Split(second, ",")
+			for _, option := range options {
+				if strings.TrimSpace(option) == first {
+					return true
+				}
+			}
+			return false
+		}
+	}
+	return first == second
+}
+
+// sanitizeAndResolve sanitizes and resolves a list of elements and returns the list of parameters as well as a list
+// of resolved parameters
+func sanitizeAndResolve(elements []string, result *Result) ([]string, []string) {
+	parameters := make([]string, len(elements))
+	resolvedParameters := make([]string, len(elements))
+	body := strings.TrimSpace(string(result.body))
+	for i, element := range elements {
+		element = strings.TrimSpace(element)
+		parameters[i] = element
+		switch strings.ToUpper(element) {
+		case StatusPlaceholder:
+			element = strconv.Itoa(result.HTTPStatus)
+		case IPPlaceholder:
+			element = result.IP
+		case ResponseTimePlaceholder:
+			element = strconv.Itoa(int(result.Duration.Milliseconds()))
+		case BodyPlaceholder:
+			element = body
+		case DNSRCodePlaceholder:
+			element = result.DNSRCode
+		case ConnectedPlaceholder:
+			element = strconv.FormatBool(result.Connected)
+		case CertificateExpirationPlaceholder:
+			element = strconv.FormatInt(result.CertificateExpiration.Milliseconds(), 10)
+		default:
+			// if contains the BodyPlaceholder, then evaluate json path
+			if strings.Contains(element, BodyPlaceholder) {
+				checkingForLength := false
+				checkingForExistence := false
+				if strings.HasPrefix(element, LengthFunctionPrefix) && strings.HasSuffix(element, FunctionSuffix) {
+					checkingForLength = true
+					element = strings.TrimSuffix(strings.TrimPrefix(element, LengthFunctionPrefix), FunctionSuffix)
+				}
+				if strings.HasPrefix(element, HasFunctionPrefix) && strings.HasSuffix(element, FunctionSuffix) {
+					checkingForExistence = true
+					element = strings.TrimSuffix(strings.TrimPrefix(element, HasFunctionPrefix), FunctionSuffix)
+				}
+				resolvedElement, resolvedElementLength, err := jsonpath.Eval(strings.TrimPrefix(strings.TrimPrefix(element, BodyPlaceholder), "."), result.body)
+				if checkingForExistence {
+					if err != nil {
+						element = "false"
+					} else {
+						element = "true"
+					}
+				} else {
+					if err != nil {
+						if err.Error() != "unexpected end of JSON input" {
+							result.AddError(err.Error())
+						}
+						if checkingForLength {
+							element = LengthFunctionPrefix + element + FunctionSuffix + " " + InvalidConditionElementSuffix
+						} else {
+							element = element + " " + InvalidConditionElementSuffix
+						}
+					} else {
+						if checkingForLength {
+							element = strconv.Itoa(resolvedElementLength)
+						} else {
+							element = resolvedElement
+						}
+					}
+				}
+			}
+		}
+		resolvedParameters[i] = element
+	}
+	return parameters, resolvedParameters
+}
+
+func sanitizeAndResolveNumerical(list []string, result *Result) (parameters []string, resolvedNumericalParameters []int64) {
+	parameters, resolvedParameters := sanitizeAndResolve(list, result)
+	for _, element := range resolvedParameters {
+		if duration, err := time.ParseDuration(element); duration != 0 && err == nil {
+			resolvedNumericalParameters = append(resolvedNumericalParameters, duration.Milliseconds())
+		} else if number, err := strconv.ParseInt(element, 10, 64); err != nil {
+			// Default to 0 if the string couldn't be converted to an integer
+			resolvedNumericalParameters = append(resolvedNumericalParameters, 0)
+		} else {
+			resolvedNumericalParameters = append(resolvedNumericalParameters, number)
+		}
+	}
+	return parameters, resolvedNumericalParameters
+}
+
+func prettifyNumericalParameters(parameters []string, resolvedParameters []int64, operator string) string {
+	return prettify(parameters, []string{strconv.Itoa(int(resolvedParameters[0])), strconv.Itoa(int(resolvedParameters[1]))}, operator)
+}
+
+// XXX: make this configurable? i.e. show-resolved-conditions-on-failure
+func prettify(parameters []string, resolvedParameters []string, operator string) string {
+	// Since, in the event of an invalid path, the resolvedParameters also contain the condition itself,
+	// we'll return the resolvedParameters as-is.
+	if strings.HasSuffix(resolvedParameters[0], InvalidConditionElementSuffix) || strings.HasSuffix(resolvedParameters[1], InvalidConditionElementSuffix) {
+		return resolvedParameters[0] + " " + operator + " " + resolvedParameters[1]
+	}
+	// If using the pattern function, truncate the parameter it's being compared to if said parameter is long enough
+	if strings.HasPrefix(parameters[0], PatternFunctionPrefix) && strings.HasSuffix(parameters[0], FunctionSuffix) && len(resolvedParameters[1]) > maximumLengthBeforeTruncatingWhenComparedWithPattern {
+		resolvedParameters[1] = fmt.Sprintf("%.25s...(truncated)", resolvedParameters[1])
+	}
+	if strings.HasPrefix(parameters[1], PatternFunctionPrefix) && strings.HasSuffix(parameters[1], FunctionSuffix) && len(resolvedParameters[0]) > maximumLengthBeforeTruncatingWhenComparedWithPattern {
+		resolvedParameters[0] = fmt.Sprintf("%.25s...(truncated)", resolvedParameters[0])
+	}
+	// First element is a placeholder
+	if parameters[0] != resolvedParameters[0] && parameters[1] == resolvedParameters[1] {
+		return parameters[0] + " (" + resolvedParameters[0] + ") " + operator + " " + parameters[1]
+	}
+	// Second element is a placeholder
+	if parameters[0] == resolvedParameters[0] && parameters[1] != resolvedParameters[1] {
+		return parameters[0] + " " + operator + " " + parameters[1] + " (" + resolvedParameters[1] + ")"
+	}
+	// Both elements are placeholders...?
+	if parameters[0] != resolvedParameters[0] && parameters[1] != resolvedParameters[1] {
+		return parameters[0] + " (" + resolvedParameters[0] + ") " + operator + " " + parameters[1] + " (" + resolvedParameters[1] + ")"
+	}
+	// Neither elements are placeholders
+	return parameters[0] + " " + operator + " " + parameters[1]
+}

core/condition_bench_test.go

@@ -0,0 +1,84 @@
+package core
+
+import "testing"
+
+func BenchmarkCondition_evaluateWithBodyStringAny(b *testing.B) {
+	condition := Condition("[BODY].name == any(john.doe, jane.doe)")
+	for n := 0; n < b.N; n++ {
+		result := &Result{body: []byte("{\"name\": \"john.doe\"}")}
+		condition.evaluate(result)
+	}
+	b.ReportAllocs()
+}
+
+func BenchmarkCondition_evaluateWithBodyStringAnyFailure(b *testing.B) {
+	condition := Condition("[BODY].name == any(john.doe, jane.doe)")
+	for n := 0; n < b.N; n++ {
+		result := &Result{body: []byte("{\"name\": \"bob.doe\"}")}
+		condition.evaluate(result)
+	}
+	b.ReportAllocs()
+}
+
+func BenchmarkCondition_evaluateWithBodyString(b *testing.B) {
+	condition := Condition("[BODY].name == john.doe")
+	for n := 0; n < b.N; n++ {
+		result := &Result{body: []byte("{\"name\": \"john.doe\"}")}
+		condition.evaluate(result)
+	}
+	b.ReportAllocs()
+}
+
+func BenchmarkCondition_evaluateWithBodyStringFailure(b *testing.B) {
+	condition := Condition("[BODY].name == john.doe")
+	for n := 0; n < b.N; n++ {
+		result := &Result{body: []byte("{\"name\": \"bob.doe\"}")}
+		condition.evaluate(result)
+	}
+	b.ReportAllocs()
+}
+
+func BenchmarkCondition_evaluateWithBodyStringFailureInvalidPath(b *testing.B) {
+	condition := Condition("[BODY].user.name == bob.doe")
+	for n := 0; n < b.N; n++ {
+		result := &Result{body: []byte("{\"name\": \"bob.doe\"}")}
+		condition.evaluate(result)
+	}
+	b.ReportAllocs()
+}
+
+func BenchmarkCondition_evaluateWithBodyStringLen(b *testing.B) {
+	condition := Condition("len([BODY].name) == 8")
+	for n := 0; n < b.N; n++ {
+		result := &Result{body: []byte("{\"name\": \"john.doe\"}")}
+		condition.evaluate(result)
+	}
+	b.ReportAllocs()
+}
+
+func BenchmarkCondition_evaluateWithBodyStringLenFailure(b *testing.B) {
+	condition := Condition("len([BODY].name) == 8")
+	for n := 0; n < b.N; n++ {
+		result := &Result{body: []byte("{\"name\": \"bob.doe\"}")}
+		condition.evaluate(result)
+	}
+	b.ReportAllocs()
+}
+
+func BenchmarkCondition_evaluateWithStatus(b *testing.B) {
+	condition := Condition("[STATUS] == 200")
+	for n := 0; n < b.N; n++ {
+		result := &Result{HTTPStatus: 200}
+		condition.evaluate(result)
+	}
+	b.ReportAllocs()
+}
+
+func BenchmarkCondition_evaluateWithStatusFailure(b *testing.B) {
+	condition := Condition("[STATUS] == 200")
+	for n := 0; n < b.N; n++ {
+		result := &Result{HTTPStatus: 400}
+		condition.evaluate(result)
+	}
+	b.ReportAllocs()
+}

core/condition_result.go

@@ -0,0 +1,10 @@
+package core
+
+// ConditionResult result of a Condition
+type ConditionResult struct {
+	// Condition that was evaluated
+	Condition string `json:"condition"`
+
+	// Success whether the condition was met (successful) or not (failed)
+	Success bool `json:"success"`
+}

core/condition_test.go

@@ -0,0 +1,469 @@
+package core
+
+import (
+	"strconv"
+	"testing"
+	"time"
+)
+
+func TestCondition_evaluate(t *testing.T) {
+	type scenario struct {
+		Name            string
+		Condition       Condition
+		Result          *Result
+		ExpectedSuccess bool
+		ExpectedOutput  string
+	}
+	scenarios := []scenario{
+		{
+			Name:            "ip",
+			Condition:       Condition("[IP] == 127.0.0.1"),
+			Result:          &Result{IP: "127.0.0.1"},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[IP] == 127.0.0.1",
+		},
+		{
+			Name:            "status",
+			Condition:       Condition("[STATUS] == 200"),
+			Result:          &Result{HTTPStatus: 200},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[STATUS] == 200",
+		},
+		{
+			Name:            "status-failure",
+			Condition:       Condition("[STATUS] == 200"),
+			Result:          &Result{HTTPStatus: 500},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[STATUS] (500) == 200",
+		},
+		{
+			Name:            "status-using-less-than",
+			Condition:       Condition("[STATUS] < 300"),
+			Result:          &Result{HTTPStatus: 201},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[STATUS] < 300",
+		},
+		{
+			Name:            "status-using-less-than-failure",
+			Condition:       Condition("[STATUS] < 300"),
+			Result:          &Result{HTTPStatus: 404},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[STATUS] (404) < 300",
+		},
+		{
+			Name:            "response-time-using-less-than",
+			Condition:       Condition("[RESPONSE_TIME] < 500"),
+			Result:          &Result{Duration: 50 * time.Millisecond},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[RESPONSE_TIME] < 500",
+		},
+		{
+			Name:            "response-time-using-less-than-with-duration",
+			Condition:       Condition("[RESPONSE_TIME] < 1s"),
+			Result:          &Result{Duration: 50 * time.Millisecond},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[RESPONSE_TIME] < 1s",
+		},
+		{
+			Name:            "response-time-using-less-than-invalid",
+			Condition:       Condition("[RESPONSE_TIME] < potato"),
+			Result:          &Result{Duration: 50 * time.Millisecond},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[RESPONSE_TIME] (50) < potato (0)", // Non-numerical values automatically resolve to 0
+		},
+		{
+			Name:            "response-time-using-greater-than",
+			Condition:       Condition("[RESPONSE_TIME] > 500"),
+			Result:          &Result{Duration: 750 * time.Millisecond},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[RESPONSE_TIME] > 500",
+		},
+		{
+			Name:            "response-time-using-greater-than-with-duration",
+			Condition:       Condition("[RESPONSE_TIME] > 1s"),
+			Result:          &Result{Duration: 2 * time.Second},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[RESPONSE_TIME] > 1s",
+		},
+		{
+			Name:            "response-time-using-greater-than-or-equal-to-equal",
+			Condition:       Condition("[RESPONSE_TIME] >= 500"),
+			Result:          &Result{Duration: 500 * time.Millisecond},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[RESPONSE_TIME] >= 500",
+		},
+		{
+			Name:            "response-time-using-greater-than-or-equal-to-greater",
+			Condition:       Condition("[RESPONSE_TIME] >= 500"),
+			Result:          &Result{Duration: 499 * time.Millisecond},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[RESPONSE_TIME] (499) >= 500",
+		},
+		{
+			Name:            "response-time-using-greater-than-or-equal-to-failure",
+			Condition:       Condition("[RESPONSE_TIME] >= 500"),
+			Result:          &Result{Duration: 499 * time.Millisecond},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[RESPONSE_TIME] (499) >= 500",
+		},
+		{
+			Name:            "response-time-using-less-than-or-equal-to-equal",
+			Condition:       Condition("[RESPONSE_TIME] <= 500"),
+			Result:          &Result{Duration: 500 * time.Millisecond},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[RESPONSE_TIME] <= 500",
+		},
+		{
+			Name:            "response-time-using-less-than-or-equal-to-less",
+			Condition:       Condition("[RESPONSE_TIME] <= 500"),
+			Result:          &Result{Duration: 25 * time.Millisecond},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[RESPONSE_TIME] <= 500",
+		},
+		{
+			Name:            "response-time-using-less-than-or-equal-to-failure",
+			Condition:       Condition("[RESPONSE_TIME] <= 500"),
+			Result:          &Result{Duration: 750 * time.Millisecond},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[RESPONSE_TIME] (750) <= 500",
+		},
+		{
+			Name:            "body",
+			Condition:       Condition("[BODY] == test"),
+			Result:          &Result{body: []byte("test")},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[BODY] == test",
+		},
+		{
+			Name:            "body-jsonpath",
+			Condition:       Condition("[BODY].status == UP"),
+			Result:          &Result{body: []byte("{\"status\":\"UP\"}")},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[BODY].status == UP",
+		},
+		{
+			Name:            "body-jsonpath-complex",
+			Condition:       Condition("[BODY].data.name == john"),
+			Result:          &Result{body: []byte("{\"data\": {\"id\": 1, \"name\": \"john\"}}")},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[BODY].data.name == john",
+		},
+		{
+			Name:            "body-jsonpath-complex-invalid",
+			Condition:       Condition("[BODY].data.name == john"),
+			Result:          &Result{body: []byte("{\"data\": {\"id\": 1}}")},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[BODY].data.name (INVALID) == john",
+		},
+		{
+			Name:            "body-jsonpath-complex-len",
+			Condition:       Condition("len([BODY].data.name) == 4"),
+			Result:          &Result{body: []byte("{\"data\": {\"name\": \"john\"}}")},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "len([BODY].data.name) == 4",
+		},
+		{
+			Name:            "body-jsonpath-complex-len-invalid",
+			Condition:       Condition("len([BODY].data.name) == john"),
+			Result:          &Result{body: []byte("{\"data\": {\"id\": 1}}")},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "len([BODY].data.name) (INVALID) == john",
+		},
+		{
+			Name:            "body-jsonpath-double-placeholder",
+			Condition:       Condition("[BODY].user.firstName != [BODY].user.lastName"),
+			Result:          &Result{body: []byte("{\"user\": {\"firstName\": \"john\", \"lastName\": \"doe\"}}")},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[BODY].user.firstName != [BODY].user.lastName",
+		},
+		{
+			Name:            "body-jsonpath-double-placeholder-failure",
+			Condition:       Condition("[BODY].user.firstName == [BODY].user.lastName"),
+			Result:          &Result{body: []byte("{\"user\": {\"firstName\": \"john\", \"lastName\": \"doe\"}}")},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[BODY].user.firstName (john) == [BODY].user.lastName (doe)",
+		},
+		{
+			Name:            "body-jsonpath-when-body-is-array",
+			Condition:       Condition("[BODY][0].id == 1"),
+			Result:          &Result{body: []byte("[{\"id\": 1}, {\"id\": 2}]")},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[BODY][0].id == 1",
+		},
+		{
+			Name:            "body-jsonpath-complex-int",
+			Condition:       Condition("[BODY].data.id == 1"),
+			Result:          &Result{body: []byte("{\"data\": {\"id\": 1}}")},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[BODY].data.id == 1",
+		},
+		{
+			Name:            "body-jsonpath-complex-array-int",
+			Condition:       Condition("[BODY].data[1].id == 2"),
+			Result:          &Result{body: []byte("{\"data\": [{\"id\": 1}, {\"id\": 2}, {\"id\": 3}]}")},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[BODY].data[1].id == 2",
+		},
+		{
+			Name:            "body-jsonpath-complex-int-using-greater-than",
+			Condition:       Condition("[BODY].data.id > 0"),
+			Result:          &Result{body: []byte("{\"data\": {\"id\": 1}}")},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[BODY].data.id > 0",
+		},
+		{
+			Name:            "body-jsonpath-complex-int-using-greater-than-failure",
+			Condition:       Condition("[BODY].data.id > 5"),
+			Result:          &Result{body: []byte("{\"data\": {\"id\": 1}}")},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[BODY].data.id (1) > 5",
+		},
+		{
+			Name:            "body-jsonpath-complex-int-using-less-than",
+			Condition:       Condition("[BODY].data.id < 5"),
+			Result:          &Result{body: []byte("{\"data\": {\"id\": 2}}")},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[BODY].data.id < 5",
+		},
+		{
+			Name:            "body-jsonpath-complex-int-using-less-than-failure",
+			Condition:       Condition("[BODY].data.id < 5"),
+			Result:          &Result{body: []byte("{\"data\": {\"id\": 10}}")},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[BODY].data.id (10) < 5",
+		},
+		{
+			Name:            "body-len-array",
+			Condition:       Condition("len([BODY].data) == 3"),
+			Result:          &Result{body: []byte("{\"data\": [{\"id\": 1}, {\"id\": 2}, {\"id\": 3}]}")},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "len([BODY].data) == 3",
+		},
+		{
+			Name:            "body-len-array-invalid",
+			Condition:       Condition("len([BODY].data) == 8"),
+			Result:          &Result{body: []byte("{\"name\": \"john.doe\"}")},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "len([BODY].data) (INVALID) == 8",
+		},
+		{
+			Name:            "body-len-string",
+			Condition:       Condition("len([BODY].name) == 8"),
+			Result:          &Result{body: []byte("{\"name\": \"john.doe\"}")},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "len([BODY].name) == 8",
+		},
+		{
+			Name:            "body-pattern",
+			Condition:       Condition("[BODY] == pat(*john*)"),
+			Result:          &Result{body: []byte("{\"name\": \"john.doe\"}")},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[BODY] == pat(*john*)",
+		},
+		{
+			Name:            "body-pattern-2",
+			Condition:       Condition("[BODY].name == pat(john*)"),
+			Result:          &Result{body: []byte("{\"name\": \"john.doe\"}")},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[BODY].name == pat(john*)",
+		},
+		{
+			Name:            "body-pattern-failure",
+			Condition:       Condition("[BODY].name == pat(bob*)"),
+			Result:          &Result{body: []byte("{\"name\": \"john.doe\"}")},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[BODY].name (john.doe) == pat(bob*)",
+		},
+		{
+			Name:            "body-pattern-html",
+			Condition:       Condition("[BODY] == pat(*<div id=\"user\">john.doe</div>*)"),
+			Result:          &Result{body: []byte(`<!DOCTYPE html><html lang="en"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /></head><body><div id="user">john.doe</div></body></html>`)},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[BODY] == pat(*<div id=\"user\">john.doe</div>*)",
+		},
+		{
+			Name:            "body-pattern-html-failure",
+			Condition:       Condition("[BODY] == pat(*<div id=\"user\">john.doe</div>*)"),
+			Result:          &Result{body: []byte(`<!DOCTYPE html><html lang="en"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /></head><body><div id="user">jane.doe</div></body></html>`)},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[BODY] (<!DOCTYPE html><html lang...(truncated)) == pat(*<div id=\"user\">john.doe</div>*)",
+		},
+		{
+			Name:            "body-pattern-html-failure-alt",
+			Condition:       Condition("pat(*<div id=\"user\">john.doe</div>*) == [BODY]"),
+			Result:          &Result{body: []byte(`<!DOCTYPE html><html lang="en"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /></head><body><div id="user">jane.doe</div></body></html>`)},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "pat(*<div id=\"user\">john.doe</div>*) == [BODY] (<!DOCTYPE html><html lang...(truncated))",
+		},
+		{
+			Name:            "ip-pattern",
+			Condition:       Condition("[IP] == pat(10.*)"),
+			Result:          &Result{IP: "10.0.0.0"},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[IP] == pat(10.*)",
+		},
+		{
+			Name:            "ip-pattern-failure",
+			Condition:       Condition("[IP] == pat(10.*)"),
+			Result:          &Result{IP: "255.255.255.255"},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[IP] (255.255.255.255) == pat(10.*)",
+		},
+		{
+			Name:            "status-pattern",
+			Condition:       Condition("[STATUS] == pat(4*)"),
+			Result:          &Result{HTTPStatus: 404},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[STATUS] == pat(4*)",
+		},
+		{
+			Name:            "status-pattern-failure",
+			Condition:       Condition("[STATUS] == pat(4*)"),
+			Result:          &Result{HTTPStatus: 200},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[STATUS] (200) == pat(4*)",
+		},
+		{
+			Name:            "body-any",
+			Condition:       Condition("[BODY].name == any(john.doe, jane.doe)"),
+			Result:          &Result{body: []byte("{\"name\": \"john.doe\"}")},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[BODY].name == any(john.doe, jane.doe)",
+		},
+		{
+			Name:            "body-any-2",
+			Condition:       Condition("[BODY].name == any(john.doe, jane.doe)"),
+			Result:          &Result{body: []byte("{\"name\": \"jane.doe\"}")},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[BODY].name == any(john.doe, jane.doe)",
+		},
+		{
+			Name:            "body-any-failure",
+			Condition:       Condition("[BODY].name == any(john.doe, jane.doe)"),
+			Result:          &Result{body: []byte("{\"name\": \"bob\"}")},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[BODY].name (bob) == any(john.doe, jane.doe)",
+		},
+		{
+			Name:            "status-any",
+			Condition:       Condition("[STATUS] == any(200, 429)"),
+			Result:          &Result{HTTPStatus: 200},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[STATUS] == any(200, 429)",
+		},
+		{
+			Name:            "status-any-2",
+			Condition:       Condition("[STATUS] == any(200, 429)"),
+			Result:          &Result{HTTPStatus: 429},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[STATUS] == any(200, 429)",
+		},
+		{
+			Name:            "status-any-reverse",
+			Condition:       Condition("any(200, 429) == [STATUS]"),
+			Result:          &Result{HTTPStatus: 429},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "any(200, 429) == [STATUS]",
+		},
+		{
+			Name:            "status-any-failure",
+			Condition:       Condition("[STATUS] == any(200, 429)"),
+			Result:          &Result{HTTPStatus: 404},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[STATUS] (404) == any(200, 429)",
+		},
+		{
+			Name:            "connected",
+			Condition:       Condition("[CONNECTED] == true"),
+			Result:          &Result{Connected: true},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[CONNECTED] == true",
+		},
+		{
+			Name:            "connected-failure",
+			Condition:       Condition("[CONNECTED] == true"),
+			Result:          &Result{Connected: false},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[CONNECTED] (false) == true",
+		},
+		{
+			Name:            "certificate-expiration-not-set",
+			Condition:       Condition("[CERTIFICATE_EXPIRATION] == 0"),
+			Result:          &Result{},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[CERTIFICATE_EXPIRATION] == 0",
+		},
+		{
+			Name:            "certificate-expiration-greater-than-numerical",
+			Condition:       Condition("[CERTIFICATE_EXPIRATION] > " + strconv.FormatInt((time.Hour*24*28).Milliseconds(), 10)),
+			Result:          &Result{CertificateExpiration: time.Hour * 24 * 60},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[CERTIFICATE_EXPIRATION] > 2419200000",
+		},
+		{
+			Name:            "certificate-expiration-greater-than-numerical-failure",
+			Condition:       Condition("[CERTIFICATE_EXPIRATION] > " + strconv.FormatInt((time.Hour*24*28).Milliseconds(), 10)),
+			Result:          &Result{CertificateExpiration: time.Hour * 24 * 14},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[CERTIFICATE_EXPIRATION] (1209600000) > 2419200000",
+		},
+		{
+			Name:            "certificate-expiration-greater-than-duration",
+			Condition:       Condition("[CERTIFICATE_EXPIRATION] > 12h"),
+			Result:          &Result{CertificateExpiration: 24 * time.Hour},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "[CERTIFICATE_EXPIRATION] > 12h",
+		},
+		{
+			Name:            "certificate-expiration-greater-than-duration",
+			Condition:       Condition("[CERTIFICATE_EXPIRATION] > 48h"),
+			Result:          &Result{CertificateExpiration: 24 * time.Hour},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "[CERTIFICATE_EXPIRATION] (86400000) > 48h (172800000)",
+		},
+		{
+			Name:            "has",
+			Condition:       Condition("has([BODY].errors) == false"),
+			Result:          &Result{body: []byte("{}")},
+			ExpectedSuccess: true,
+			ExpectedOutput:  "has([BODY].errors) == false",
+		},
+		{
+			Name:            "has-failure",
+			Condition:       Condition("has([BODY].errors) == false"),
+			Result:          &Result{body: []byte("{\"errors\": [\"1\"]}")},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "has([BODY].errors) (true) == false",
+		},
+		{
+			Name:            "no-placeholders",
+			Condition:       Condition("1 == 2"),
+			Result:          &Result{},
+			ExpectedSuccess: false,
+			ExpectedOutput:  "1 == 2",
+		},
+	}
+	for _, scenario := range scenarios {
+		t.Run(scenario.Name, func(t *testing.T) {
+			scenario.Condition.evaluate(scenario.Result)
+			if scenario.Result.ConditionResults[0].Success != scenario.ExpectedSuccess {
+				t.Errorf("Condition '%s' should have been success=%v", scenario.Condition, scenario.ExpectedSuccess)
+			}
+			if scenario.Result.ConditionResults[0].Condition != scenario.ExpectedOutput {
+				t.Errorf("Condition '%s' should have resolved to '%s', got '%s'", scenario.Condition, scenario.ExpectedOutput, scenario.Result.ConditionResults[0].Condition)
+			}
+		})
+	}
+}
+
+func TestCondition_evaluateWithInvalidOperator(t *testing.T) {
+	condition := Condition("[STATUS] ? 201")
+	result := &Result{HTTPStatus: 201}
+	condition.evaluate(result)
+	if result.Success {
+		t.Error("condition was invalid, result should've been a failure")
+	}
+	if len(result.Errors) != 1 {
+		t.Error("condition was invalid, result should've had an error")
+	}
+}

core/dns.go

@@ -0,0 +1,86 @@
+package core
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/miekg/dns"
+)
+
+var (
+	// ErrDNSWithNoQueryName is the error with which gatus will panic if a dns is configured without query name
+	ErrDNSWithNoQueryName = errors.New("you must specify a query name for DNS")
+
+	// ErrDNSWithInvalidQueryType is the error with which gatus will panic if a dns is configured with invalid query type
+	ErrDNSWithInvalidQueryType = errors.New("invalid query type")
+)
+
+const (
+	dnsPort = 53
+)
+
+// DNS is the configuration for a Service of type DNS
+type DNS struct {
+	// QueryType is the type for the DNS records like A, AAAA, CNAME...
+	QueryType string `yaml:"query-type"`
+
+	// QueryName is the query for DNS
+	QueryName string `yaml:"query-name"`
+}
+
+func (d *DNS) validateAndSetDefault() error {
+	if len(d.QueryName) == 0 {
+		return ErrDNSWithNoQueryName
+	}
+	if !strings.HasSuffix(d.QueryName, ".") {
+		d.QueryName += "."
+	}
+	if _, ok := dns.StringToType[d.QueryType]; !ok {
+		return ErrDNSWithInvalidQueryType
+	}
+	return nil
+}
+
+func (d *DNS) query(url string, result *Result) {
+	if !strings.Contains(url, ":") {
+		url = fmt.Sprintf("%s:%d", url, dnsPort)
+	}
+	queryType := dns.StringToType[d.QueryType]
+	c := new(dns.Client)
+	m := new(dns.Msg)
+	m.SetQuestion(d.QueryName, queryType)
+	r, _, err := c.Exchange(m, url)
+	if err != nil {
+		result.AddError(err.Error())
+		return
+	}
+	result.Connected = true
+	result.DNSRCode = dns.RcodeToString[r.Rcode]
+	for _, rr := range r.Answer {
+		switch rr.Header().Rrtype {
+		case dns.TypeA:
+			if a, ok := rr.(*dns.A); ok {
+				result.body = []byte(a.A.String())
+			}
+		case dns.TypeAAAA:
+			if aaaa, ok := rr.(*dns.AAAA); ok {
+				result.body = []byte(aaaa.AAAA.String())
+			}
+		case dns.TypeCNAME:
+			if cname, ok := rr.(*dns.CNAME); ok {
+				result.body = []byte(cname.Target)
+			}
+		case dns.TypeMX:
+			if mx, ok := rr.(*dns.MX); ok {
+				result.body = []byte(mx.Mx)
+			}
+		case dns.TypeNS:
+			if ns, ok := rr.(*dns.NS); ok {
+				result.body = []byte(ns.Ns)
+			}
+		default:
+			result.body = []byte("query type is not supported yet")
+		}
+	}
+}

core/dns_test.go

@@ -0,0 +1,128 @@
+package core
+
+import (
+	"testing"
+
+	"github.com/TwinProduction/gatus/pattern"
+)
+
+func TestIntegrationQuery(t *testing.T) {
+	tests := []struct {
+		name            string
+		inputDNS        DNS
+		inputURL        string
+		expectedDNSCode string
+		expectedBody    string
+		isErrExpected   bool
+	}{
+		{
+			name: "test DNS with type A",
+			inputDNS: DNS{
+				QueryType: "A",
+				QueryName: "example.com.",
+			},
+			inputURL:        "8.8.8.8",
+			expectedDNSCode: "NOERROR",
+			expectedBody:    "93.184.216.34",
+		},
+		{
+			name: "test DNS with type AAAA",
+			inputDNS: DNS{
+				QueryType: "AAAA",
+				QueryName: "example.com.",
+			},
+			inputURL:        "8.8.8.8",
+			expectedDNSCode: "NOERROR",
+			expectedBody:    "2606:2800:220:1:248:1893:25c8:1946",
+		},
+		{
+			name: "test DNS with type CNAME",
+			inputDNS: DNS{
+				QueryType: "CNAME",
+				QueryName: "doc.google.com.",
+			},
+			inputURL:        "8.8.8.8",
+			expectedDNSCode: "NOERROR",
+			expectedBody:    "writely.l.google.com.",
+		},
+		{
+			name: "test DNS with type MX",
+			inputDNS: DNS{
+				QueryType: "MX",
+				QueryName: "example.com.",
+			},
+			inputURL:        "8.8.8.8",
+			expectedDNSCode: "NOERROR",
+			expectedBody:    ".",
+		},
+		{
+			name: "test DNS with type NS",
+			inputDNS: DNS{
+				QueryType: "NS",
+				QueryName: "example.com.",
+			},
+			inputURL:        "8.8.8.8",
+			expectedDNSCode: "NOERROR",
+			expectedBody:    "*.iana-servers.net.",
+		},
+		{
+			name: "test DNS with fake type and retrieve error",
+			inputDNS: DNS{
+				QueryType: "B",
+				QueryName: "google",
+			},
+			inputURL:      "8.8.8.8",
+			isErrExpected: true,
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			dns := test.inputDNS
+			result := &Result{}
+			dns.query(test.inputURL, result)
+			if test.isErrExpected && len(result.Errors) == 0 {
+				t.Errorf("there should be errors")
+			}
+			if result.DNSRCode != test.expectedDNSCode {
+				t.Errorf("DNSRCodePlaceholder '%s' should have been %s", result.DNSRCode, test.expectedDNSCode)
+			}
+
+			if test.inputDNS.QueryType == "NS" {
+				// Because there are often multiple nameservers backing a single domain, we'll only look at the suffix
+				if !pattern.Match(test.expectedBody, string(result.body)) {
+					t.Errorf("got %s, expected result %s,", string(result.body), test.expectedBody)
+				}
+			} else {
+				if string(result.body) != test.expectedBody {
+					t.Errorf("got %s, expected result %s,", string(result.body), test.expectedBody)
+				}
+			}
+		})
+	}
+}
+
+func TestService_ValidateAndSetDefaultsWithNoDNSQueryName(t *testing.T) {
+	defer func() { recover() }()
+	dns := &DNS{
+		QueryType: "A",
+		QueryName: "",
+	}
+	err := dns.validateAndSetDefault()
+	if err == nil {
+		t.Fatal("Should've returned an error because service`s dns didn't have a query name, which is a mandatory field for dns")
+	}
+}
+
+func TestService_ValidateAndSetDefaultsWithInvalidDNSQueryType(t *testing.T) {
+	defer func() { recover() }()
+	dns := &DNS{
+		QueryType: "B",
+		QueryName: "example.com",
+	}
+	err := dns.validateAndSetDefault()
+	if err == nil {
+		t.Fatal("Should've returned an error because service`s dns query type is invalid, it needs to be a valid query name like A, AAAA, CNAME...")
+	}
+}

core/event.go

@@ -0,0 +1,37 @@
+package core
+
+import "time"
+
+// Event is something that happens at a specific time
+type Event struct {
+	// Type is the kind of event
+	Type EventType `json:"type"`
+
+	// Timestamp is the moment at which the event happened
+	Timestamp time.Time `json:"timestamp"`
+}
+
+// EventType is, uh, the types of events?
+type EventType string
+
+var (
+	// EventStart is a type of event that represents when a service starts being monitored
+	EventStart EventType = "START"
+
+	// EventHealthy is a type of event that represents a service passing all of its conditions
+	EventHealthy EventType = "HEALTHY"
+
+	// EventUnhealthy is a type of event that represents a service failing one or more of its conditions
+	EventUnhealthy EventType = "UNHEALTHY"
+)
+
+// NewEventFromResult creates an Event from a Result
+func NewEventFromResult(result *Result) *Event {
+	event := &Event{Timestamp: result.Timestamp}
+	if result.Success {
+		event.Type = EventHealthy
+	} else {
+		event.Type = EventUnhealthy
+	}
+	return event
+}

core/health_status.go

@@ -0,0 +1,11 @@
+package core
+
+// HealthStatus is the status of Gatus
+type HealthStatus struct {
+	// Status is the state of Gatus (UP/DOWN)
+	Status string `json:"status"`
+
+	// Message is an accompanying description of why the status is as reported.
+	// If the Status is UP, no message will be provided
+	Message string `json:"message,omitempty"`
+}

core/result.go

@@ -0,0 +1,60 @@
+package core
+
+import (
+	"time"
+)
+
+// Result of the evaluation of a Service
+type Result struct {
+	// HTTPStatus is the HTTP response status code
+	HTTPStatus int `json:"status"`
+
+	// DNSRCode is the response code of a DNS query in a human readable format
+	DNSRCode string `json:"-"`
+
+	// Hostname extracted from Service.URL
+	Hostname string `json:"hostname"`
+
+	// IP resolved from the Service URL
+	IP string `json:"-"`
+
+	// Connected whether a connection to the host was established successfully
+	Connected bool `json:"-"`
+
+	// Duration time that the request took
+	Duration time.Duration `json:"duration"`
+
+	// Errors encountered during the evaluation of the service's health
+	Errors []string `json:"errors"`
+
+	// ConditionResults results of the service's conditions
+	ConditionResults []*ConditionResult `json:"conditionResults"`
+
+	// Success whether the result signifies a success or not
+	Success bool `json:"success"`
+
+	// Timestamp when the request was sent
+	Timestamp time.Time `json:"timestamp"`
+
+	// CertificateExpiration is the duration before the certificate expires
+	CertificateExpiration time.Duration `json:"-"`
+
+	// body is the response body
+	//
+	// Note that this variable is only used during the evaluation of a service's health.
+	// This means that the call Service.EvaluateHealth both populates the body (if necessary)
+	// and sets it to nil after the evaluation has been completed.
+	body []byte
+}
+
+// AddError adds an error to the result's list of errors.
+// It also ensures that there are no duplicates.
+func (r *Result) AddError(error string) {
+	for _, resultError := range r.Errors {
+		if resultError == error {
+			// If the error already exists, don't add it
+			return
+		}
+	}
+	r.Errors = append(r.Errors, error)
+}

core/result_test.go

@@ -0,0 +1,21 @@
+package core
+
+import (
+	"testing"
+)
+
+func TestResult_AddError(t *testing.T) {
+	result := &Result{}
+	result.AddError("potato")
+	if len(result.Errors) != 1 {
+		t.Error("should've had 1 error")
+	}
+	result.AddError("potato")
+	if len(result.Errors) != 1 {
+		t.Error("should've still had 1 error, because a duplicate error was added")
+	}
+	result.AddError("tomato")
+	if len(result.Errors) != 2 {
+		t.Error("should've had 2 error")
+	}
+}

core/service.go

@@ -0,0 +1,283 @@
+package core
+
+import (
+	"bytes"
+	"crypto/x509"
+	"encoding/json"
+	"errors"
+	"io/ioutil"
+	"log"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/client"
+	"github.com/TwinProduction/gatus/util"
+)
+
+const (
+	// HostHeader is the name of the header used to specify the host
+	HostHeader = "Host"
+
+	// ContentTypeHeader is the name of the header used to specify the content type
+	ContentTypeHeader = "Content-Type"
+
+	// UserAgentHeader is the name of the header used to specify the request's user agent
+	UserAgentHeader = "User-Agent"
+
+	// GatusUserAgent is the default user agent that Gatus uses to send requests.
+	GatusUserAgent = "Gatus/1.0"
+)
+
+var (
+	// ErrServiceWithNoCondition is the error with which Gatus will panic if a service is configured with no conditions
+	ErrServiceWithNoCondition = errors.New("you must specify at least one condition per service")
+
+	// ErrServiceWithNoURL is the error with which Gatus will panic if a service is configured with no url
+	ErrServiceWithNoURL = errors.New("you must specify an url for each service")
+
+	// ErrServiceWithNoName is the error with which Gatus will panic if a service is configured with no name
+	ErrServiceWithNoName = errors.New("you must specify a name for each service")
+)
+
+// Service is the configuration of a monitored endpoint
+type Service struct {
+	// Name of the service. Can be anything.
+	Name string `yaml:"name"`
+
+	// Group the service is a part of. Used for grouping multiple services together on the front end.
+	Group string `yaml:"group,omitempty"`
+
+	// URL to send the request to
+	URL string `yaml:"url"`
+
+	// DNS is the configuration of DNS monitoring
+	DNS *DNS `yaml:"dns,omitempty"`
+
+	// Method of the request made to the url of the service
+	Method string `yaml:"method,omitempty"`
+
+	// Body of the request
+	Body string `yaml:"body,omitempty"`
+
+	// GraphQL is whether to wrap the body in a query param ({"query":"$body"})
+	GraphQL bool `yaml:"graphql,omitempty"`
+
+	// Headers of the request
+	Headers map[string]string `yaml:"headers,omitempty"`
+
+	// Interval is the duration to wait between every status check
+	Interval time.Duration `yaml:"interval,omitempty"`
+
+	// Conditions used to determine the health of the service
+	Conditions []*Condition `yaml:"conditions"`
+
+	// Alerts is the alerting configuration for the service in case of failure
+	Alerts []*alert.Alert `yaml:"alerts"`
+
+	// Insecure is whether to skip verifying the server's certificate chain and host name
+	//
+	// deprecated
+	Insecure bool `yaml:"insecure,omitempty"`
+
+	// ClientConfig is the configuration of the client used to communicate with the service's target
+	ClientConfig *client.Config `yaml:"client"`
+
+	// NumberOfFailuresInARow is the number of unsuccessful evaluations in a row
+	NumberOfFailuresInARow int
+
+	// NumberOfSuccessesInARow is the number of successful evaluations in a row
+	NumberOfSuccessesInARow int
+}
+
+// ValidateAndSetDefaults validates the service's configuration and sets the default value of fields that have one
+func (service *Service) ValidateAndSetDefaults() error {
+	// Set default values
+	if service.ClientConfig == nil {
+		service.ClientConfig = client.GetDefaultConfig()
+		// XXX: remove the next 3 lines in v3.0.0
+		if service.Insecure {
+			log.Println("WARNING: services[].insecure has been deprecated and will be removed in v3.0.0 in favor of services[].client.insecure")
+			service.ClientConfig.Insecure = true
+		}
+	} else {
+		service.ClientConfig.ValidateAndSetDefaults()
+	}
+	if service.Interval == 0 {
+		service.Interval = 1 * time.Minute
+	}
+	if len(service.Method) == 0 {
+		service.Method = http.MethodGet
+	}
+	if len(service.Headers) == 0 {
+		service.Headers = make(map[string]string)
+	}
+	// Automatically add user agent header if there isn't one specified in the service configuration
+	if _, userAgentHeaderExists := service.Headers[UserAgentHeader]; !userAgentHeaderExists {
+		service.Headers[UserAgentHeader] = GatusUserAgent
+	}
+	// Automatically add "Content-Type: application/json" header if there's no Content-Type set
+	// and service.GraphQL is set to true
+	if _, contentTypeHeaderExists := service.Headers[ContentTypeHeader]; !contentTypeHeaderExists && service.GraphQL {
+		service.Headers[ContentTypeHeader] = "application/json"
+	}
+	for _, serviceAlert := range service.Alerts {
+		if serviceAlert.FailureThreshold <= 0 {
+			serviceAlert.FailureThreshold = 3
+		}
+		if serviceAlert.SuccessThreshold <= 0 {
+			serviceAlert.SuccessThreshold = 2
+		}
+	}
+	if len(service.Name) == 0 {
+		return ErrServiceWithNoName
+	}
+	if len(service.URL) == 0 {
+		return ErrServiceWithNoURL
+	}
+	if len(service.Conditions) == 0 {
+		return ErrServiceWithNoCondition
+	}
+	if service.DNS != nil {
+		return service.DNS.validateAndSetDefault()
+	}
+	// Make sure that the request can be created
+	_, err := http.NewRequest(service.Method, service.URL, bytes.NewBuffer([]byte(service.Body)))
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// Key returns the unique key for the Service
+func (service Service) Key() string {
+	return util.ConvertGroupAndServiceToKey(service.Group, service.Name)
+}
+
+// EvaluateHealth sends a request to the service's URL and evaluates the conditions of the service.
+func (service *Service) EvaluateHealth() *Result {
+	result := &Result{Success: true, Errors: []string{}}
+	service.getIP(result)
+	if len(result.Errors) == 0 {
+		service.call(result)
+	} else {
+		result.Success = false
+	}
+	for _, condition := range service.Conditions {
+		success := condition.evaluate(result)
+		if !success {
+			result.Success = false
+		}
+	}
+	result.Timestamp = time.Now()
+	// No need to keep the body after the service has been evaluated
+	result.body = nil
+	return result
+}
+
+func (service *Service) getIP(result *Result) {
+	if service.DNS != nil {
+		result.Hostname = strings.TrimSuffix(service.URL, ":53")
+	} else {
+		urlObject, err := url.Parse(service.URL)
+		if err != nil {
+			result.AddError(err.Error())
+			return
+		}
+		result.Hostname = urlObject.Hostname()
+	}
+	ips, err := net.LookupIP(result.Hostname)
+	if err != nil {
+		result.AddError(err.Error())
+		return
+	}
+	result.IP = ips[0].String()
+}
+
+func (service *Service) call(result *Result) {
+	var request *http.Request
+	var response *http.Response
+	var err error
+	var certificate *x509.Certificate
+	isServiceDNS := service.DNS != nil
+	isServiceTCP := strings.HasPrefix(service.URL, "tcp://")
+	isServiceICMP := strings.HasPrefix(service.URL, "icmp://")
+	isServiceStartTLS := strings.HasPrefix(service.URL, "starttls://")
+	isServiceHTTP := !isServiceDNS && !isServiceTCP && !isServiceICMP && !isServiceStartTLS
+	if isServiceHTTP {
+		request = service.buildHTTPRequest()
+	}
+	startTime := time.Now()
+	if isServiceDNS {
+		service.DNS.query(service.URL, result)
+		result.Duration = time.Since(startTime)
+	} else if isServiceStartTLS {
+		result.Connected, certificate, err = client.CanPerformStartTLS(strings.TrimPrefix(service.URL, "starttls://"), service.ClientConfig)
+		if err != nil {
+			result.AddError(err.Error())
+			return
+		}
+		result.Duration = time.Since(startTime)
+		result.CertificateExpiration = time.Until(certificate.NotAfter)
+	} else if isServiceTCP {
+		result.Connected = client.CanCreateTCPConnection(strings.TrimPrefix(service.URL, "tcp://"), service.ClientConfig)
+		result.Duration = time.Since(startTime)
+	} else if isServiceICMP {
+		result.Connected, result.Duration = client.Ping(strings.TrimPrefix(service.URL, "icmp://"), service.ClientConfig)
+	} else {
+		response, err = client.GetHTTPClient(service.ClientConfig).Do(request)
+		result.Duration = time.Since(startTime)
+		if err != nil {
+			result.AddError(err.Error())
+			return
+		}
+		defer response.Body.Close()
+		if response.TLS != nil && len(response.TLS.PeerCertificates) > 0 {
+			certificate = response.TLS.PeerCertificates[0]
+			result.CertificateExpiration = time.Until(certificate.NotAfter)
+		}
+		result.HTTPStatus = response.StatusCode
+		result.Connected = response.StatusCode > 0
+		// Only read the body if there's a condition that uses the BodyPlaceholder
+		if service.needsToReadBody() {
+			result.body, err = ioutil.ReadAll(response.Body)
+			if err != nil {
+				result.AddError(err.Error())
+			}
+		}
+	}
+}
+
+func (service *Service) buildHTTPRequest() *http.Request {
+	var bodyBuffer *bytes.Buffer
+	if service.GraphQL {
+		graphQlBody := map[string]string{
+			"query": service.Body,
+		}
+		body, _ := json.Marshal(graphQlBody)
+		bodyBuffer = bytes.NewBuffer(body)
+	} else {
+		bodyBuffer = bytes.NewBuffer([]byte(service.Body))
+	}
+	request, _ := http.NewRequest(service.Method, service.URL, bodyBuffer)
+	for k, v := range service.Headers {
+		request.Header.Set(k, v)
+		if k == HostHeader {
+			request.Host = v
+		}
+	}
+	return request
+}
+
+// needsToReadBody checks if there's any conditions that requires the response body to be read
+func (service *Service) needsToReadBody() bool {
+	for _, condition := range service.Conditions {
+		if condition.hasBodyPlaceholder() {
+			return true
+		}
+	}
+	return false
+}

core/service_status.go

@@ -0,0 +1,46 @@
+package core
+
+// ServiceStatus contains the evaluation Results of a Service
+type ServiceStatus struct {
+	// Name of the service
+	Name string `json:"name,omitempty"`
+
+	// Group the service is a part of. Used for grouping multiple services together on the front end.
+	Group string `json:"group,omitempty"`
+
+	// Key is the key representing the ServiceStatus
+	Key string `json:"key"`
+
+	// Results is the list of service evaluation results
+	Results []*Result `json:"results"`
+
+	// Events is a list of events
+	//
+	// We don't expose this through JSON, because the main dashboard doesn't need to have this data.
+	// However, the detailed service page does leverage this by including it to a map that will be
+	// marshalled alongside the ServiceStatus.
+	Events []*Event `json:"-"`
+
+	// Uptime information on the service's uptime
+	//
+	// We don't expose this through JSON, because the main dashboard doesn't need to have this data.
+	// However, the detailed service page does leverage this by including it to a map that will be
+	// marshalled alongside the ServiceStatus.
+	//
+	// TODO: Get rid of this in favor of using the new store.GetUptimeByKey.
+	// TODO: For memory, store the uptime in a different map? (is that possible, given that we need to persist it through gocache?)
+	// Deprecated
+	Uptime *Uptime `json:"-"`
+}
+
+// NewServiceStatus creates a new ServiceStatus
+func NewServiceStatus(serviceKey, serviceGroup, serviceName string) *ServiceStatus {
+	return &ServiceStatus{
+		Name:    serviceName,
+		Group:   serviceGroup,
+		Key:     serviceKey,
+		Results: make([]*Result, 0),
+		Events:  make([]*Event, 0),
+		Uptime:  NewUptime(),
+	}
+}

core/service_status_test.go

@@ -0,0 +1,19 @@
+package core
+
+import (
+	"testing"
+)
+
+func TestNewServiceStatus(t *testing.T) {
+	service := &Service{Name: "name", Group: "group"}
+	serviceStatus := NewServiceStatus(service.Key(), service.Group, service.Name)
+	if serviceStatus.Name != service.Name {
+		t.Errorf("expected %s, got %s", service.Name, serviceStatus.Name)
+	}
+	if serviceStatus.Group != service.Group {
+		t.Errorf("expected %s, got %s", service.Group, serviceStatus.Group)
+	}
+	if serviceStatus.Key != "group_name" {
+		t.Errorf("expected %s, got %s", "group_name", serviceStatus.Key)
+	}
+}

core/service_test.go

@@ -0,0 +1,364 @@
+package core
+
+import (
+	"io/ioutil"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/TwinProduction/gatus/alerting/alert"
+	"github.com/TwinProduction/gatus/client"
+)
+
+func TestService_ValidateAndSetDefaults(t *testing.T) {
+	condition := Condition("[STATUS] == 200")
+	service := Service{
+		Name:       "twinnation-health",
+		URL:        "https://twinnation.org/health",
+		Conditions: []*Condition{&condition},
+		Alerts:     []*alert.Alert{{Type: alert.TypePagerDuty}},
+	}
+	service.ValidateAndSetDefaults()
+	if service.ClientConfig == nil {
+		t.Error("client configuration should've been set to the default configuration")
+	} else {
+		if service.ClientConfig.Insecure != client.GetDefaultConfig().Insecure {
+			t.Errorf("Default client configuration should've set Insecure to %v, got %v", client.GetDefaultConfig().Insecure, service.ClientConfig.Insecure)
+		}
+		if service.ClientConfig.IgnoreRedirect != client.GetDefaultConfig().IgnoreRedirect {
+			t.Errorf("Default client configuration should've set IgnoreRedirect to %v, got %v", client.GetDefaultConfig().IgnoreRedirect, service.ClientConfig.IgnoreRedirect)
+		}
+		if service.ClientConfig.Timeout != client.GetDefaultConfig().Timeout {
+			t.Errorf("Default client configuration should've set Timeout to %v, got %v", client.GetDefaultConfig().Timeout, service.ClientConfig.Timeout)
+		}
+	}
+	if service.Method != "GET" {
+		t.Error("Service method should've defaulted to GET")
+	}
+	if service.Interval != time.Minute {
+		t.Error("Service interval should've defaulted to 1 minute")
+	}
+	if service.Headers == nil {
+		t.Error("Service headers should've defaulted to an empty map")
+	}
+	if len(service.Alerts) != 1 {
+		t.Error("Service should've had 1 alert")
+	}
+	if service.Alerts[0].IsEnabled() {
+		t.Error("Service alert should've defaulted to disabled")
+	}
+	if service.Alerts[0].SuccessThreshold != 2 {
+		t.Error("Service alert should've defaulted to a success threshold of 2")
+	}
+	if service.Alerts[0].FailureThreshold != 3 {
+		t.Error("Service alert should've defaulted to a failure threshold of 3")
+	}
+}
+
+func TestService_ValidateAndSetDefaultsWithClientConfig(t *testing.T) {
+	condition := Condition("[STATUS] == 200")
+	service := Service{
+		Name:       "twinnation-health",
+		URL:        "https://twinnation.org/health",
+		Conditions: []*Condition{&condition},
+		ClientConfig: &client.Config{
+			Insecure:       true,
+			IgnoreRedirect: true,
+			Timeout:        0,
+		},
+	}
+	service.ValidateAndSetDefaults()
+	if service.ClientConfig == nil {
+		t.Error("client configuration should've been set to the default configuration")
+	} else {
+		if !service.ClientConfig.Insecure {
+			t.Error("service.ClientConfig.Insecure should've been set to true")
+		}
+		if !service.ClientConfig.IgnoreRedirect {
+			t.Error("service.ClientConfig.IgnoreRedirect should've been set to true")
+		}
+		if service.ClientConfig.Timeout != client.GetDefaultConfig().Timeout {
+			t.Error("service.ClientConfig.Timeout should've been set to 10s, because the timeout value entered is not set or invalid")
+		}
+	}
+}
+
+func TestService_ValidateAndSetDefaultsWithNoName(t *testing.T) {
+	defer func() { recover() }()
+	condition := Condition("[STATUS] == 200")
+	service := &Service{
+		Name:       "",
+		URL:        "http://example.com",
+		Conditions: []*Condition{&condition},
+	}
+	err := service.ValidateAndSetDefaults()
+	if err == nil {
+		t.Fatal("Should've returned an error because service didn't have a name, which is a mandatory field")
+	}
+}
+
+func TestService_ValidateAndSetDefaultsWithNoUrl(t *testing.T) {
+	defer func() { recover() }()
+	condition := Condition("[STATUS] == 200")
+	service := &Service{
+		Name:       "example",
+		URL:        "",
+		Conditions: []*Condition{&condition},
+	}
+	err := service.ValidateAndSetDefaults()
+	if err == nil {
+		t.Fatal("Should've returned an error because service didn't have an url, which is a mandatory field")
+	}
+}
+
+func TestService_ValidateAndSetDefaultsWithNoConditions(t *testing.T) {
+	defer func() { recover() }()
+	service := &Service{
+		Name:       "example",
+		URL:        "http://example.com",
+		Conditions: nil,
+	}
+	err := service.ValidateAndSetDefaults()
+	if err == nil {
+		t.Fatal("Should've returned an error because service didn't have at least 1 condition")
+	}
+}
+
+func TestService_ValidateAndSetDefaultsWithDNS(t *testing.T) {
+	conditionSuccess := Condition("[DNS_RCODE] == NOERROR")
+	service := &Service{
+		Name: "dns-test",
+		URL:  "http://example.com",
+		DNS: &DNS{
+			QueryType: "A",
+			QueryName: "example.com",
+		},
+		Conditions: []*Condition{&conditionSuccess},
+	}
+	err := service.ValidateAndSetDefaults()
+	if err != nil {
+
+	}
+	if service.DNS.QueryName != "example.com." {
+		t.Error("Service.dns.query-name should be formatted with . suffix")
+	}
+}
+
+func TestService_buildHTTPRequest(t *testing.T) {
+	condition := Condition("[STATUS] == 200")
+	service := Service{
+		Name:       "twinnation-health",
+		URL:        "https://twinnation.org/health",
+		Conditions: []*Condition{&condition},
+	}
+	service.ValidateAndSetDefaults()
+	request := service.buildHTTPRequest()
+	if request.Method != "GET" {
+		t.Error("request.Method should've been GET, but was", request.Method)
+	}
+	if request.Host != "twinnation.org" {
+		t.Error("request.Host should've been twinnation.org, but was", request.Host)
+	}
+	if userAgent := request.Header.Get("User-Agent"); userAgent != GatusUserAgent {
+		t.Errorf("request.Header.Get(User-Agent) should've been %s, but was %s", GatusUserAgent, userAgent)
+	}
+}
+
+func TestService_buildHTTPRequestWithCustomUserAgent(t *testing.T) {
+	condition := Condition("[STATUS] == 200")
+	service := Service{
+		Name:       "twinnation-health",
+		URL:        "https://twinnation.org/health",
+		Conditions: []*Condition{&condition},
+		Headers: map[string]string{
+			"User-Agent": "Test/2.0",
+		},
+	}
+	service.ValidateAndSetDefaults()
+	request := service.buildHTTPRequest()
+	if request.Method != "GET" {
+		t.Error("request.Method should've been GET, but was", request.Method)
+	}
+	if request.Host != "twinnation.org" {
+		t.Error("request.Host should've been twinnation.org, but was", request.Host)
+	}
+	if userAgent := request.Header.Get("User-Agent"); userAgent != "Test/2.0" {
+		t.Errorf("request.Header.Get(User-Agent) should've been %s, but was %s", "Test/2.0", userAgent)
+	}
+}
+
+func TestService_buildHTTPRequestWithHostHeader(t *testing.T) {
+	condition := Condition("[STATUS] == 200")
+	service := Service{
+		Name:       "twinnation-health",
+		URL:        "https://twinnation.org/health",
+		Method:     "POST",
+		Conditions: []*Condition{&condition},
+		Headers: map[string]string{
+			"Host": "example.com",
+		},
+	}
+	service.ValidateAndSetDefaults()
+	request := service.buildHTTPRequest()
+	if request.Method != "POST" {
+		t.Error("request.Method should've been POST, but was", request.Method)
+	}
+	if request.Host != "example.com" {
+		t.Error("request.Host should've been example.com, but was", request.Host)
+	}
+}
+
+func TestService_buildHTTPRequestWithGraphQLEnabled(t *testing.T) {
+	condition := Condition("[STATUS] == 200")
+	service := Service{
+		Name:       "twinnation-graphql",
+		URL:        "https://twinnation.org/graphql",
+		Method:     "POST",
+		Conditions: []*Condition{&condition},
+		GraphQL:    true,
+		Body: `{
+  users(gender: "female") {
+    id
+    name
+    gender
+    avatar
+  }
+}`,
+	}
+	service.ValidateAndSetDefaults()
+	request := service.buildHTTPRequest()
+	if request.Method != "POST" {
+		t.Error("request.Method should've been POST, but was", request.Method)
+	}
+	if contentType := request.Header.Get(ContentTypeHeader); contentType != "application/json" {
+		t.Error("request.Header.Content-Type should've been application/json, but was", contentType)
+	}
+	body, _ := ioutil.ReadAll(request.Body)
+	if !strings.HasPrefix(string(body), "{\"query\":") {
+		t.Error("request.body should've started with '{\"query\":', but it didn't:", string(body))
+	}
+}
+
+func TestIntegrationEvaluateHealth(t *testing.T) {
+	condition := Condition("[STATUS] == 200")
+	bodyCondition := Condition("[BODY].status == UP")
+	service := Service{
+		Name:       "twinnation-health",
+		URL:        "https://twinnation.org/health",
+		Conditions: []*Condition{&condition, &bodyCondition},
+	}
+	service.ValidateAndSetDefaults()
+	result := service.EvaluateHealth()
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+	if !result.Connected {
+		t.Error("Because the connection has been established, result.Connected should've been true")
+	}
+	if !result.Success {
+		t.Error("Because all conditions passed, this should have been a success")
+	}
+}
+
+func TestIntegrationEvaluateHealthWithFailure(t *testing.T) {
+	condition := Condition("[STATUS] == 500")
+	service := Service{
+		Name:       "twinnation-health",
+		URL:        "https://twinnation.org/health",
+		Conditions: []*Condition{&condition},
+	}
+	service.ValidateAndSetDefaults()
+	result := service.EvaluateHealth()
+	if result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a failure", condition)
+	}
+	if !result.Connected {
+		t.Error("Because the connection has been established, result.Connected should've been true")
+	}
+	if result.Success {
+		t.Error("Because one of the conditions failed, success should have been false")
+	}
+}
+
+func TestIntegrationEvaluateHealthForDNS(t *testing.T) {
+	conditionSuccess := Condition("[DNS_RCODE] == NOERROR")
+	conditionBody := Condition("[BODY] == 93.184.216.34")
+	service := Service{
+		Name: "example",
+		URL:  "8.8.8.8",
+		DNS: &DNS{
+			QueryType: "A",
+			QueryName: "example.com.",
+		},
+		Conditions: []*Condition{&conditionSuccess, &conditionBody},
+	}
+	service.ValidateAndSetDefaults()
+	result := service.EvaluateHealth()
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Conditions '%s' and %s should have been a success", conditionSuccess, conditionBody)
+	}
+	if !result.Connected {
+		t.Error("Because the connection has been established, result.Connected should've been true")
+	}
+	if !result.Success {
+		t.Error("Because all conditions passed, this should have been a success")
+	}
+}
+
+func TestIntegrationEvaluateHealthForICMP(t *testing.T) {
+	conditionSuccess := Condition("[CONNECTED] == true")
+	service := Service{
+		Name:       "icmp-test",
+		URL:        "icmp://127.0.0.1",
+		Conditions: []*Condition{&conditionSuccess},
+	}
+	service.ValidateAndSetDefaults()
+	result := service.EvaluateHealth()
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Conditions '%s' should have been a success", conditionSuccess)
+	}
+	if !result.Connected {
+		t.Error("Because the connection has been established, result.Connected should've been true")
+	}
+	if !result.Success {
+		t.Error("Because all conditions passed, this should have been a success")
+	}
+}
+
+func TestService_getIP(t *testing.T) {
+	conditionSuccess := Condition("[CONNECTED] == true")
+	service := Service{
+		Name:       "invalid-url-test",
+		URL:        "",
+		Conditions: []*Condition{&conditionSuccess},
+	}
+	result := &Result{}
+	service.getIP(result)
+	if len(result.Errors) == 0 {
+		t.Error("service.getIP(result) should've thrown an error because the URL is invalid, thus cannot be parsed")
+	}
+}
+
+func TestService_NeedsToReadBody(t *testing.T) {
+	statusCondition := Condition("[STATUS] == 200")
+	bodyCondition := Condition("[BODY].status == UP")
+	bodyConditionWithLength := Condition("len([BODY].tags) > 0")
+	if (&Service{Conditions: []*Condition{&statusCondition}}).needsToReadBody() {
+		t.Error("expected false, got true")
+	}
+	if !(&Service{Conditions: []*Condition{&bodyCondition}}).needsToReadBody() {
+		t.Error("expected true, got false")
+	}
+	if !(&Service{Conditions: []*Condition{&bodyConditionWithLength}}).needsToReadBody() {
+		t.Error("expected true, got false")
+	}
+	if !(&Service{Conditions: []*Condition{&statusCondition, &bodyCondition}}).needsToReadBody() {
+		t.Error("expected true, got false")
+	}
+	if !(&Service{Conditions: []*Condition{&bodyCondition, &statusCondition}}).needsToReadBody() {
+		t.Error("expected true, got false")
+	}
+	if !(&Service{Conditions: []*Condition{&bodyConditionWithLength, &statusCondition}}).needsToReadBody() {
+		t.Error("expected true, got false")
+	}
+}

core/types.go

@@ -1,152 +0,0 @@
-package core
-
-import (
-	"fmt"
-	"net"
-	"net/http"
-	"net/url"
-	"strconv"
-	"strings"
-	"time"
-)
-
-type HealthStatus struct {
-	Status  string `json:"status"`
-	Message string `json:"message,omitempty"`
-}
-
-type ServerMessage struct {
-	Error   bool   `json:"error"`
-	Message string `json:"message"`
-}
-
-type Result struct {
-	HttpStatus       int                `json:"status"`
-	Hostname         string             `json:"hostname"`
-	Ip               string             `json:"ip"`
-	Duration         time.Duration      `json:"duration"`
-	Errors           []string           `json:"errors"`
-	ConditionResults []*ConditionResult `json:"condition-results"`
-	Success          bool               `json:"success"`
-	Timestamp        time.Time          `json:"timestamp"`
-}
-
-type Service struct {
-	Name       string        `yaml:"name"`
-	Url        string        `yaml:"url"`
-	Interval   time.Duration `yaml:"interval,omitempty"`
-	Conditions []*Condition  `yaml:"conditions"`
-}
-
-func (service *Service) getIp(result *Result) {
-	urlObject, err := url.Parse(service.Url)
-	if err != nil {
-		result.Errors = append(result.Errors, err.Error())
-		return
-	}
-	result.Hostname = urlObject.Hostname()
-	ips, err := net.LookupIP(urlObject.Hostname())
-	if err != nil {
-		result.Errors = append(result.Errors, err.Error())
-		return
-	}
-	result.Ip = ips[0].String()
-}
-
-func (service *Service) getStatus(result *Result) {
-	client := &http.Client{
-		Timeout: time.Second * 10,
-	}
-	startTime := time.Now()
-	response, err := client.Get(service.Url)
-	if err != nil {
-		result.Errors = append(result.Errors, err.Error())
-		return
-	}
-	result.Duration = time.Now().Sub(startTime)
-	result.HttpStatus = response.StatusCode
-}
-
-func (service *Service) EvaluateConditions() *Result {
-	result := &Result{Success: true, Errors: []string{}}
-	service.getIp(result)
-	if len(result.Errors) == 0 {
-		service.getStatus(result)
-	} else {
-		result.Success = false
-	}
-	for _, condition := range service.Conditions {
-		success := condition.Evaluate(result)
-		if !success {
-			result.Success = false
-		}
-	}
-	result.Timestamp = time.Now()
-	return result
-}
-
-type ConditionResult struct {
-	Condition   *Condition `json:"condition"`
-	Success     bool       `json:"success"`
-	Explanation string     `json:"explanation"`
-}
-
-type Condition string
-
-func (c *Condition) Evaluate(result *Result) bool {
-	condition := string(*c)
-	if strings.Contains(condition, "==") {
-		parts := sanitizeAndResolve(strings.Split(condition, "=="), result)
-		if parts[0] == parts[1] {
-			result.ConditionResults = append(result.ConditionResults, &ConditionResult{
-				Condition:   c,
-				Success:     true,
-				Explanation: fmt.Sprintf("%s is equal to %s", parts[0], parts[1]),
-			})
-			return true
-		} else {
-			result.ConditionResults = append(result.ConditionResults, &ConditionResult{
-				Condition:   c,
-				Success:     false,
-				Explanation: fmt.Sprintf("%s is not equal to %s", parts[0], parts[1]),
-			})
-			return false
-		}
-	} else if strings.Contains(condition, "!=") {
-		parts := sanitizeAndResolve(strings.Split(condition, "!="), result)
-		if parts[0] != parts[1] {
-			result.ConditionResults = append(result.ConditionResults, &ConditionResult{
-				Condition:   c,
-				Success:     true,
-				Explanation: fmt.Sprintf("%s is not equal to %s", parts[0], parts[1]),
-			})
-			return true
-		} else {
-			result.ConditionResults = append(result.ConditionResults, &ConditionResult{
-				Condition:   c,
-				Success:     false,
-				Explanation: fmt.Sprintf("%s is equal to %s", parts[0], parts[1]),
-			})
-			return false
-		}
-	} else {
-		result.Errors = append(result.Errors, fmt.Sprintf("invalid condition '%s' has been provided", condition))
-		return false
-	}
-}
-
-func sanitizeAndResolve(list []string, result *Result) []string {
-	var sanitizedList []string
-	for _, element := range list {
-		element = strings.TrimSpace(element)
-		switch strings.ToUpper(element) {
-		case "[STATUS]":
-			element = strconv.Itoa(result.HttpStatus)
-		case "[IP]":
-			element = result.Ip
-		default:
-		}
-		sanitizedList = append(sanitizedList, element)
-	}
-	return sanitizedList
-}

core/types_test.go

@@ -1,64 +0,0 @@
-package core
-
-import (
-	"testing"
-)
-
-func TestEvaluateWithIp(t *testing.T) {
-	condition := Condition("[IP] == 127.0.0.1")
-	result := &Result{Ip: "127.0.0.1"}
-	condition.Evaluate(result)
-	if !result.ConditionResults[0].Success {
-		t.Errorf("Condition '%s' should have been a success", condition)
-	}
-}
-
-func TestEvaluateWithStatus(t *testing.T) {
-	condition := Condition("[STATUS] == 201")
-	result := &Result{HttpStatus: 201}
-	condition.Evaluate(result)
-	if !result.ConditionResults[0].Success {
-		t.Errorf("Condition '%s' should have been a success", condition)
-	}
-}
-
-func TestEvaluateWithFailure(t *testing.T) {
-	condition := Condition("[STATUS] == 200")
-	result := &Result{HttpStatus: 500}
-	condition.Evaluate(result)
-	if result.ConditionResults[0].Success {
-		t.Errorf("Condition '%s' should have been a failure", condition)
-	}
-}
-
-func TestIntegrationEvaluateConditions(t *testing.T) {
-	condition := Condition("[STATUS] == 200")
-	service := Service{
-		Name:       "GitHub",
-		Url:        "https://api.github.com/healthz",
-		Conditions: []*Condition{&condition},
-	}
-	result := service.EvaluateConditions()
-	if !result.ConditionResults[0].Success {
-		t.Errorf("Condition '%s' should have been a success", condition)
-	}
-	if !result.Success {
-		t.Error("Because all conditions passed, this should have been a success")
-	}
-}
-
-func TestIntegrationEvaluateConditionsWithFailure(t *testing.T) {
-	condition := Condition("[STATUS] == 500")
-	service := Service{
-		Name:       "GitHub",
-		Url:        "https://api.github.com/healthz",
-		Conditions: []*Condition{&condition},
-	}
-	result := service.EvaluateConditions()
-	if result.ConditionResults[0].Success {
-		t.Errorf("Condition '%s' should have been a failure", condition)
-	}
-	if result.Success {
-		t.Error("Because one of the conditions failed, success should have been false")
-	}
-}

core/uptime.go

@@ -0,0 +1,34 @@
+package core
+
+// Uptime is the struct that contains the relevant data for calculating the uptime as well as the uptime itself
+// and some other statistics
+type Uptime struct {
+	// SuccessfulExecutionsPerHour is a map containing the number of successes (value)
+	// for every hourly unix timestamps (key)
+	// Deprecated
+	SuccessfulExecutionsPerHour map[int64]uint64 `json:"-"`
+
+	// TotalExecutionsPerHour is a map containing the total number of checks (value)
+	// for every hourly unix timestamps (key)
+	// Deprecated
+	TotalExecutionsPerHour map[int64]uint64 `json:"-"`
+
+	// HourlyStatistics is a map containing metrics collected (value) for every hourly unix timestamps (key)
+	//
+	// Used only if the storage type is memory
+	HourlyStatistics map[int64]*HourlyUptimeStatistics `json:"-"`
+}
+
+// HourlyUptimeStatistics is a struct containing all metrics collected over the course of an hour
+type HourlyUptimeStatistics struct {
+	TotalExecutions             uint64 // Total number of checks
+	SuccessfulExecutions        uint64 // Number of successful executions
+	TotalExecutionsResponseTime uint64 // Total response time for all executions
+}
+
+// NewUptime creates a new Uptime
+func NewUptime() *Uptime {
+	return &Uptime{
+		HourlyStatistics: make(map[int64]*HourlyUptimeStatistics),
+	}
+}

docs/pagerduty-integration-guide.md

@@ -0,0 +1,74 @@
+# PagerDuty + Gatus Integration Benefits
+- Notify on-call responders based on alerts sent from Gatus.
+- Incidents will automatically resolve in PagerDuty when the service that caused the incident in Gatus returns to a healthy state.
+
+
+# How it Works
+- Services that do not meet the user-specified conditions and that are configured with alerts of type `pagerduty` will trigger a new incident on the corresponding PagerDuty service when the alert's defined `failure-threshold` has been reached.
+- Once the unhealthy services have returned to a healthy state for the number of executions defined in `success-threshold`, the previously triggered incident will be automatically resolved.
+
+
+# Requirements
+- PagerDuty integrations require an Admin base role for account authorization. If you do not have this role, please reach out to an Admin or Account Owner within your organization to configure the integration.
+
+
+# Support
+If you need help with this integration, please create an issue at https://github.com/TwinProduction/gatus/issues
+
+
+# Integration Walkthrough
+## In PagerDuty
+### Integrating With a PagerDuty Service
+1. From the **Configuration** menu, select **Services**.
+2. There are two ways to add an integration to a service:
+   * **If you are adding your integration to an existing service**: Click the **name** of the service you want to add the integration to. Then, select the **Integrations** tab and click the **New Integration** button.
+   * **If you are creating a new service for your integration**: Please read our documentation in section [Configuring Services and Integrations](https://support.pagerduty.com/docs/services-and-integrations#section-configuring-services-and-integrations) and follow the steps outlined in the [Create a New Service](https://support.pagerduty.com/docs/services-and-integrations#section-create-a-new-service) section, selecting **Gatus** as the **Integration Type** in step 4. Continue with the In Gatus section (below) once you have finished these steps.
+3. Enter an **Integration Name** in the format `gatus-service-name` (e.g. `Gatus-Shopping-Cart`) and select **Gatus** from the Integration Type menu.
+4. Click the **Add Integration** button to save your new integration. You will be redirected to the Integrations tab for your service.
+5. An **Integration Key** will be generated on this screen. Keep this key saved in a safe place, as it will be used when you configure the integration with **Gatus** in the next section.
+![PagerDuty Integration Key](https://raw.githubusercontent.com/TwinProduction/gatus/master/.github/assets/pagerduty-integration-key.png)
+
+
+## In Gatus
+In your configuration file, you must first specify the integration key at `alerting.pagerduty.integration-key`, like so:
+```yaml
+alerting:
+  pagerduty: 
+    integration-key: "********************************"
+```
+You can now add alerts of type `pagerduty` in the services you've defined, like so:
+```yaml
+services:
+  - name: twinnation
+    interval: 30s
+    url: "https://twinnation.org/health"
+    alerts:
+      - type: pagerduty
+        enabled: true
+        failure-threshold: 3
+        success-threshold: 5
+        description: "healthcheck failed 3 times in a row"
+        send-on-resolved: true
+    conditions:
+      - "[STATUS] == 200"
+      - "[BODY].status == UP"
+      - "[RESPONSE_TIME] < 300"
+```
+
+The sample above will do the following:
+- Send a request to the `https://twinnation.org/health` (`services[].url`) specified every **30s** (`services[].interval`)
+- Evaluate the conditions to determine whether the service is "healthy" or not
+- **If all conditions are not met 3 (`services[].alerts[].failure-threshold`) times in a row**: Gatus will create a new incident
+- **If, after an incident has been triggered, all conditions are met 5 (`services[].alerts[].success-threshold`) times in a row _AND_ `services[].alerts[].send-on-resolved` is set to `true`**: Gatus will resolve the triggered incident
+
+It is highly recommended to set `services[].alerts[].send-on-resolved` to true for alerts of type `pagerduty`.
+
+
+# How to Uninstall
+1. Navigate to the PagerDuty service you'd like to uninstall the Gatus integration from
+2. Click on the **Integration** tab
+3. Click on the **Gatus** integration
+4. Click on **Delete Integration**
+
+While the above will prevent incidents from being created, you are also highly encouraged to disable the alerts
+in your Gatus configuration files or simply remove the integration key from the configuration file.

examples/docker-compose-grafana-prometheus/config.yaml

@@ -1,12 +1,13 @@
 metrics: true
 services:
   - name: TwiNNatioN
-    url: https://twinnation.org/actuator/health
-    interval: 10s
+    url: https://twinnation.org/health
+    interval: 30s
     conditions:
       - "[STATUS] == 200"
   - name: GitHub
     url: https://api.github.com/healthz
+    interval: 5m
     conditions:
       - "[STATUS] == 200"
   - name: Example

examples/docker-compose-mattermost/config.yaml

@@ -0,0 +1,16 @@
+alerting:
+  mattermost:
+    webhook-url: "http://mattermost:8065/hooks/tokengoeshere"
+    insecure: true
+
+services:
+  - name: example
+    url: http://example.org
+    interval: 1m
+    alerts:
+      - type: mattermost
+        enabled: true
+        description: "healthcheck failed 3 times in a row"
+        send-on-resolved: true
+    conditions:
+      - "[STATUS] == 200"

examples/docker-compose-mattermost/docker-compose.yml

@@ -0,0 +1,24 @@
+version: "3.8"
+
+services:
+  gatus:
+    container_name: gatus
+    image: twinproduction/gatus:latest
+    ports:
+      - 8080:8080
+    volumes:
+      - ./config.yaml:/config/config.yaml
+    networks:
+      - default
+
+  mattermost:
+    container_name: mattermost
+    image: mattermost/mattermost-preview:5.26.0
+    ports:
+      - 8065:8065
+    networks:
+      - default
+
+networks:
+  default:
+    driver: bridge

examples/docker-compose-sqlite-storage/config.yaml

@@ -0,0 +1,42 @@
+storage:
+  type: sqlite
+  file: /data/data.db
+
+services:
+  - name: back-end
+    group: core
+    url: "https://example.org/"
+    interval: 5m
+    conditions:
+      - "[STATUS] == 200"
+      - "[CERTIFICATE_EXPIRATION] > 48h"
+
+  - name: monitoring
+    group: internal
+    url: "https://example.org/"
+    interval: 5m
+    conditions:
+      - "[STATUS] == 200"
+
+  - name: nas
+    group: internal
+    url: "https://example.org/"
+    interval: 5m
+    conditions:
+      - "[STATUS] == 200"
+
+  - name: example-dns-query
+    url: "8.8.8.8" # Address of the DNS server to use
+    interval: 5m
+    dns:
+      query-name: "example.com"
+      query-type: "A"
+    conditions:
+      - "[BODY] == 93.184.216.34"
+      - "[DNS_RCODE] == NOERROR"
+
+  - name: icmp-ping
+    url: "icmp://example.org"
+    interval: 1m
+    conditions:
+      - "[CONNECTED] == true"

examples/docker-compose-sqlite-storage/docker-compose.yml

@@ -0,0 +1,9 @@
+version: "3.8"
+services:
+  gatus:
+    image: twinproduction/gatus:latest
+    ports:
+      - 8080:8080
+    volumes:
+      - ./config.yaml:/config/config.yaml
+      - ./data:/data/

examples/docker-compose/docker-compose.yml

@@ -0,0 +1,8 @@
+version: "3.8"
+services:
+  gatus:
+    image: twinproduction/gatus:latest
+    ports:
+      - 8080:8080
+    volumes:
+      - ./config.yaml:/config/config.yaml

examples/kubernetes-with-auto-discovery/gatus.yaml

@@ -0,0 +1,109 @@
+apiVersion: v1
+data:
+  config.yaml: |
+    kubernetes:
+      cluster-mode: "in"
+      auto-discover: true
+      excluded-service-suffixes:
+        - canary
+      service-template:
+        interval: 30s
+        conditions:
+          - "[STATUS] == 200"
+      namespaces:
+        - name: default
+          hostname-suffix: ".default.svc.cluster.local"
+          target-path: "/health"
+          excluded-services:
+            - gatus
+kind: ConfigMap
+metadata:
+  name: gatus
+  namespace: kube-system
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRole
+metadata:
+  name: gatus
+rules:
+  - apiGroups:
+      - ""
+    resources:
+      - services
+    verbs:
+      - list
+      - get
+---
+apiVersion: v1
+automountServiceAccountToken: true
+kind: ServiceAccount
+metadata:
+  name: gatus
+  namespace: kube-system
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRoleBinding
+metadata:
+  name: gatus
+roleRef:
+  apiGroup: rbac.authorization.k8s.io
+  kind: ClusterRole
+  name: gatus
+subjects:
+  - kind: ServiceAccount
+    name: gatus
+    namespace: kube-system
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: gatus
+  namespace: kube-system
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      k8s-app: gatus
+  template:
+    metadata:
+      labels:
+        k8s-app: gatus
+      name: gatus
+      namespace: kube-system
+    spec:
+      containers:
+        - image: twinproduction/gatus
+          imagePullPolicy: IfNotPresent
+          name: gatus
+          ports:
+            - containerPort: 8080
+              name: http
+              protocol: TCP
+          resources:
+            limits:
+              cpu: 250m
+              memory: 100M
+            requests:
+              cpu: 50m
+              memory: 30M
+          volumeMounts:
+            - mountPath: /config
+              name: gatus-config
+      volumes:
+        - configMap:
+            name: gatus
+          name: gatus-config
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: gatus
+  namespace: kube-system
+spec:
+  ports:
+    - name: http
+      port: 8080
+      protocol: TCP
+      targetPort: 8080
+  selector:
+    k8s-app: gatus