Support custom alert provider

Note that arrays are not currently supported, same with asterisks

.github/workflows/build.yml

@@ -0,0 +1,27 @@
+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 1.14
+        uses: actions/setup-go@v1
+        with:
+          go-version: 1.14
+        id: go
+      - name: Check out code into the Go module directory
+        uses: actions/checkout@v1
+      - name: Build binary to make sure it works
+        run: go build -mod vendor
+      - name: Test
+        run: go test -mod vendor -cover ./...

.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

LICENSE.md

@@ -186,7 +186,7 @@
       same "printed page" as the copyright notice for easier
       identification within third-party archives.
 
-   Copyright [yyyy] [name of copyright owner]
+   Copyright 2020 TwinProduction
 
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.

README.md

@@ -1,25 +1,51 @@
-# gatus
+![Gatus](static/logo-with-name.png)
 
+![build](https://github.com/TwinProduction/gatus/workflows/build/badge.svg?branch=master)
+[![Go Report Card](https://goreportcard.com/badge/github.com/TwinProduction/gatus)](https://goreportcard.com/report/github.com/TwinProduction/gatus)
 [![Docker pulls](https://img.shields.io/docker/pulls/twinproduction/gatus.svg)](https://cloud.docker.com/repository/docker/twinproduction/gatus)
 
 A service health dashboard in Go that is meant to be used as a docker 
 image with a custom configuration file.
 
-Live example: https://status.twinnation.org/
+I personally deploy it in my Kubernetes cluster and have it monitor the status of my
+core applications: https://status.twinnation.org/
+
+
+## Table of Contents
+
+- [Usage](#usage)
+  - [Configuration](#configuration)
+  - [Conditions](#conditions)
+- [Docker](#docker)
+- [Running the tests](#running-the-tests)
+- [Using in Production](#using-in-production)
+- [FAQ](#faq)
+  - [Sending a GraphQL request](#sending-a-graphql-request)
+  - [Configuring Slack alerts](#configuring-slack-alerts)
+  - [Configuring custom alert](#configuring-custom-alerts)
 
 
 ## Usage
 
+By default, the configuration file is expected to be at `config/config.yaml`.
+
+You can specify a custom path by setting the `GATUS_CONFIG_FILE` environment variable.
+
+Here's a simple example:
+
 ```yaml
 metrics: true         # Whether to expose metrics at /metrics
 services:
   - name: twinnation  # Name of your service, can be anything
-    url: https://twinnation.org/actuator/health
-    interval: 15s     # Duration to wait between every status check (opt. default: 10s)
+    url: "https://twinnation.org/health"
+    interval: 30s     # Duration to wait between every status check (default: 10s)
     conditions:
-      - "[STATUS] == 200"
-  - name: github
-    url: https://api.github.com/healthz
+      - "[STATUS] == 200"         # Status must be 200
+      - "[BODY].status == UP"     # The json path "$.status" must be equal to UP
+      - "[RESPONSE_TIME] < 300"   # Response time must be under 300ms
+  - name: example
+    url: "https://example.org/"
+    interval: 30s
     conditions:
       - "[STATUS] == 200"
 ```
@@ -27,6 +53,52 @@ services:
 Note that you can also add environment variables in the your configuration file (i.e. `$DOMAIN`, `${DOMAIN}`)
 
 
+### Configuration
+
+| Parameter                         | Description                                                     | Default        |
+| --------------------------------- | --------------------------------------------------------------- | -------------- |
+| `metrics`                         | Whether to expose metrics at /metrics                           | `false`        |
+| `services`                        | List of services to monitor                                     | Required `[]`  |
+| `services[].name`                 | Name of the service. Can be anything.                           | Required `""`  |
+| `services[].url`                  | URL to send the request to                                      | Required `""`  |
+| `services[].conditions`           | Conditions used to determine the health of the service          | `[]`           |
+| `services[].interval`             | Duration to wait between every status check                     | `10s`          |
+| `services[].method`               | Request method                                                  | `GET`          |
+| `services[].graphql`              | Whether to wrap the body in a query param (`{"query":"$body"}`) | `false`        |
+| `services[].body`                 | Request body                                                    | `""`           |
+| `services[].headers`              | Request headers                                                 | `{}`           |
+| `services[].alerts[].type`        | Type of alert. Valid types: `slack`, `custom`                   | Required `""`  |
+| `services[].alerts[].enabled`     | Whether to enable the alert                                     | `false`        |
+| `services[].alerts[].threshold`   | Number of failures in a row needed before triggering the alert  | `3`            |
+| `services[].alerts[].description` | Description of the alert. Will be included in the alert sent    | `""`           |
+| `alerting`                        | Configuration for alerting                                      | `{}`           |
+| `alerting.slack`                  | Webhook to use for alerts of type `slack`                       | `""`           |
+| `alerting.custom`                 | Configuration for custom actions on failure or alerts           | `""`           |
+| `alerting.custom.url`             | Custom alerting request url                                     | `""`           |
+| `alerting.custom.body`            | Custom alerting request body.                                   | `""`           |
+| `alerting.custom.headers`         | Custom alerting request headers                                 | `{}`           |
+
+
+### Conditions
+
+Here are some examples of conditions you can use:
+
+| Condition                    | Description                                             | Passing values           | Failing values          |
+| -----------------------------| ------------------------------------------------------- | ------------------------ | ----------------------- |
+| `[STATUS] == 200`            | Status must be equal to 200                             | 200                      | 201, 404, 500           |
+| `[STATUS] < 300`             | Status must lower than 300                              | 200, 201, 299            | 301, 302, 400, 500      |
+| `[STATUS] <= 299`            | Status must be less than or equal to 299                | 200, 201, 299            | 301, 302, 400, 500      |
+| `[STATUS] > 400`             | Status must be greater than 400                         | 401, 402, 403, 404       | 200, 201, 300, 400      |
+| `[RESPONSE_TIME] < 500`      | Response time must be below 500ms                       | 100ms, 200ms, 300ms      | 500ms, 1500ms           |
+| `[BODY] == 1`                | The body must be equal to 1                             | 1                        | literally anything else |
+| `[BODY].data.id == 1`        | The jsonpath `$.data.id` is equal to 1                  | `{"data":{"id":1}}`      | literally anything else |
+| `[BODY].data[0].id == 1`     | The jsonpath `$.data[0].id` is equal to 1               | `{"data":[{"id":1}]}`    | literally anything else |
+| `len([BODY].data) > 0`       | Array at jsonpath `$.data` has less than 5 elements     | `{"data":[{"id":1}]}`    | `{"data":[{"id":1}]}`   |
+| `len([BODY].name) == 8`      | String at jsonpath `$.name` has a length of 8           | `{"name":"john.doe"}`    | `{"name":"bob"}`        |
+
+**NOTE**: `[BODY]` with JSON path (i.e. `[BODY].id == 1`) is currently in BETA. For the most part, the only thing that doesn't work is arrays.
+
+
 ## Docker
 
 Building the Docker image is done as following:
@@ -52,3 +124,101 @@ go test ./... -mod vendor
 ## Using in Production
 
 See the [example](example) folder.
+
+
+## FAQ
+
+### Sending a GraphQL request
+
+By setting `services[].graphql` to true, the body will automatically be wrapped by the standard GraphQL `query` parameter.
+
+For instance, the following configuration:
+```yaml
+services:
+  - name: filter users by gender
+    url: http://localhost:8080/playground
+    method: POST
+    graphql: true
+    body: |
+      {
+        user(gender: "female") {
+          id
+          name
+          gender
+          avatar
+        }
+      }
+    headers:
+      Content-Type: application/json
+    conditions:
+      - "[STATUS] == 200"
+      - "[BODY].data.user[0].gender == female"
+```
+
+will send a `POST` request to `http://localhost:8080/playground` with the following body:
+```json
+{"query":"      {\n        user(gender: \"female\") {\n          id\n          name\n          gender\n          avatar\n        }\n      }"}
+```
+
+
+### Configuring Slack alerts
+
+```yaml
+alerting:
+  slack: "https://hooks.slack.com/services/**********/**********/**********"
+services:
+  - name: twinnation
+    interval: 30s
+    url: "https://twinnation.org/health"
+    alerts:
+      - type: slack
+        enabled: true
+        description: "healthcheck failed 3 times in a row"
+      - type: slack
+        enabled: true
+        threshold: 5
+        description: "healthcheck failed 5 times in a row"
+    conditions:
+      - "[STATUS] == 200"
+      - "[BODY].status == UP"
+      - "[RESPONSE_TIME] < 300"
+```
+
+
+### Configuring custom alerts
+
+While they're called alerts, you can use this feature to call anything. 
+
+For instance, you could automate rollbacks by having an application that keeps tracks of new deployments, and by 
+leveraging Gatus, you could have Gatus call that application endpoint when a service starts failing. Your application
+would then check if the service that started failing was recently deployed, and if it was, then automatically 
+roll it back.
+
+The values `[ALERT_DESCRIPTION]` and `[SERVICE_NAME]` are automatically substituted for the alert description and the 
+service name accordingly in the body (`alerting.custom.body`) and the url (`alerting.custom.url`).
+
+For all intents and purpose, we'll configure the custom alert with a Slack webhook, but you can call anything you want.
+
+```yaml
+alerting:
+  custom:
+    url: "https://hooks.slack.com/services/**********/**********/**********"
+    method: "POST"
+    body: |
+      {
+        "text": "[SERVICE_NAME] - [ALERT_DESCRIPTION]"
+      }
+services:
+  - name: twinnation
+    interval: 30s
+    url: "https://twinnation.org/health"
+    alerts:
+      - type: custom
+        enabled: true
+        threshold: 10
+        description: "healthcheck failed 10 times in a row"
+    conditions:
+      - "[STATUS] == 200"
+      - "[BODY].status == UP"
+      - "[RESPONSE_TIME] < 300"
+```

client/client.go

@@ -0,0 +1,19 @@
+package client
+
+import (
+	"net/http"
+	"time"
+)
+
+var (
+	client *http.Client
+)
+
+func GetHttpClient() *http.Client {
+	if client == nil {
+		client = &http.Client{
+			Timeout: time.Second * 10,
+		}
+	}
+	return client
+}

config.yaml

@@ -1,11 +1,17 @@
 metrics: true
 services:
   - name: twinnation
-    url: https://twinnation.org/actuator/health
-    interval: 15s
+    interval: 30s
+    url: https://twinnation.org/health
     conditions:
       - "[STATUS] == 200"
-  - name: github
-    url: https://api.github.com/healthz
+      - "[BODY].status == UP"
+      - "[RESPONSE_TIME] < 1000"
+  - name: twinnation-articles-api
+    interval: 30s
+    url: "https://twinnation.org/api/v1/articles/24"
     conditions:
-      - "[STATUS] == 200"
+      - "[STATUS] == 200"
+      - "[BODY].id == 24"
+      - "[BODY].tags[0] == spring"
+      - "len([BODY].tags) > 0"

config/config.go

@@ -7,13 +7,11 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
-	"time"
 )
 
-type Config struct {
-	Metrics  bool            `yaml:"metrics"`
-	Services []*core.Service `yaml:"services"`
-}
+const (
+	DefaultConfigurationFilePath = "config/config.yaml"
+)
 
 var (
 	ErrNoServiceInConfig  = errors.New("configuration file should contain at least 1 service")
@@ -22,6 +20,12 @@ var (
 	config                *Config
 )
 
+type Config struct {
+	Metrics  bool                 `yaml:"metrics"`
+	Alerting *core.AlertingConfig `yaml:"alerting"`
+	Services []*core.Service      `yaml:"services"`
+}
+
 func Get() *Config {
 	if config == nil {
 		panic(ErrConfigNotLoaded)
@@ -44,7 +48,7 @@ func Load(configFile string) error {
 }
 
 func LoadDefaultConfiguration() error {
-	err := Load("config/config.yaml")
+	err := Load(DefaultConfigurationFilePath)
 	if err != nil {
 		if err == ErrConfigFileNotFound {
 			return Load("config/config.yml")
@@ -74,9 +78,7 @@ func parseAndValidateConfigBytes(yamlBytes []byte) (config *Config, err error) {
 	} else {
 		// Set the default values if they aren't set
 		for _, service := range config.Services {
-			if service.Interval == 0 {
-				service.Interval = 10 * time.Second
-			}
+			service.Validate()
 		}
 	}
 	return

config/config_test.go

@@ -2,6 +2,7 @@ package config
 
 import (
 	"fmt"
+	"github.com/TwinProduction/gatus/core"
 	"testing"
 	"time"
 )
@@ -23,6 +24,9 @@ services:
 	if err != nil {
 		t.Error("No error should've been returned")
 	}
+	if config == nil {
+		t.Fatal("Config shouldn't have been nil")
+	}
 	if len(config.Services) != 2 {
 		t.Error("Should have returned two services")
 	}
@@ -58,6 +62,9 @@ services:
 	if err != nil {
 		t.Error("No error should've been returned")
 	}
+	if config == nil {
+		t.Fatal("Config shouldn't have been nil")
+	}
 	if config.Metrics {
 		t.Error("Metrics should've been false by default")
 	}
@@ -81,6 +88,9 @@ services:
 	if err != nil {
 		t.Error("No error should've been returned")
 	}
+	if config == nil {
+		t.Fatal("Config shouldn't have been nil")
+	}
 	if !config.Metrics {
 		t.Error("Metrics should have been true")
 	}
@@ -107,3 +117,62 @@ badconfig:
 		t.Error("The error returned should have been of type ErrNoServiceInConfig")
 	}
 }
+
+func TestParseAndValidateConfigBytesWithAlerting(t *testing.T) {
+	config, err := parseAndValidateConfigBytes([]byte(`
+alerting:
+  slack: "http://example.com"
+services:
+  - name: twinnation
+    url: https://twinnation.org/actuator/health
+    alerts:
+      - type: slack
+        enabled: true
+        threshold: 7
+        description: "Healthcheck failed 7 times in a row"
+    conditions:
+      - "[STATUS] == 200"
+`))
+	if err != nil {
+		t.Error("No error should've been returned")
+	}
+	if config == nil {
+		t.Fatal("Config shouldn't have been nil")
+	}
+	if config.Metrics {
+		t.Error("Metrics should've been false by default")
+	}
+	if config.Alerting == nil {
+		t.Fatal("config.AlertingConfig shouldn't have been nil")
+	}
+	if config.Alerting.Slack != "http://example.com" {
+		t.Errorf("Slack webhook should've been %s, but was %s", "http://example.com", config.Alerting.Slack)
+	}
+	if len(config.Services) != 1 {
+		t.Error("There should've been 1 service")
+	}
+	if config.Services[0].Url != "https://twinnation.org/actuator/health" {
+		t.Errorf("URL should have been %s", "https://twinnation.org/actuator/health")
+	}
+	if config.Services[0].Interval != 10*time.Second {
+		t.Errorf("Interval should have been %s, because it is the default value", 10*time.Second)
+	}
+	if config.Services[0].Alerts == nil {
+		t.Fatal("The service alerts shouldn't have been nil")
+	}
+	if len(config.Services[0].Alerts) != 1 {
+		t.Fatal("There should've been 1 alert configured")
+	}
+	if !config.Services[0].Alerts[0].Enabled {
+		t.Error("The alert should've been enabled")
+	}
+	if config.Services[0].Alerts[0].Threshold != 7 {
+		t.Errorf("The threshold of the alert should've been %d, but it was %d", 7, config.Services[0].Alerts[0].Threshold)
+	}
+	if config.Services[0].Alerts[0].Type != core.SlackAlert {
+		t.Errorf("The type of the alert should've been %s, but it was %s", core.SlackAlert, config.Services[0].Alerts[0].Type)
+	}
+	if config.Services[0].Alerts[0].Description != "Healthcheck failed 7 times in a row" {
+		t.Errorf("The type of the alert should've been %s, but it was %s", "Healthcheck failed 7 times in a row", config.Services[0].Alerts[0].Description)
+	}
+}

core/alert.go

@@ -0,0 +1,23 @@
+package core
+
+// Alert is the service's alert configuration
+type Alert struct {
+	// Type of alert
+	Type AlertType `yaml:"type"`
+
+	// Enabled defines whether or not the alert is enabled
+	Enabled bool `yaml:"enabled"`
+
+	// Threshold is the number of failures in a row needed before triggering the alert
+	Threshold int `yaml:"threshold"`
+
+	// Description of the alert. Will be included in the alert sent.
+	Description string `yaml:"description"`
+}
+
+type AlertType string
+
+const (
+	SlackAlert  AlertType = "slack"
+	CustomAlert AlertType = "custom"
+)

core/alerting.go

@@ -0,0 +1,56 @@
+package core
+
+import (
+	"bytes"
+	"fmt"
+	"github.com/TwinProduction/gatus/client"
+	"net/http"
+	"strings"
+)
+
+type AlertingConfig struct {
+	Slack  string               `yaml:"slack"`
+	Custom *CustomAlertProvider `yaml:"custom"`
+}
+
+type CustomAlertProvider struct {
+	Url     string            `yaml:"url"`
+	Method  string            `yaml:"method,omitempty"`
+	Body    string            `yaml:"body,omitempty"`
+	Headers map[string]string `yaml:"headers,omitempty"`
+}
+
+func (provider *CustomAlertProvider) buildRequest(serviceName, alertDescription string) *http.Request {
+	body := provider.Body
+	url := provider.Url
+	if strings.Contains(provider.Body, "[ALERT_DESCRIPTION]") {
+		body = strings.ReplaceAll(provider.Body, "[ALERT_DESCRIPTION]", alertDescription)
+	}
+	if strings.Contains(provider.Body, "[SERVICE_NAME]") {
+		body = strings.ReplaceAll(provider.Body, "[SERVICE_NAME]", serviceName)
+	}
+	if strings.Contains(provider.Url, "[ALERT_DESCRIPTION]") {
+		url = strings.ReplaceAll(provider.Url, "[ALERT_DESCRIPTION]", alertDescription)
+	}
+	if strings.Contains(provider.Url, "[SERVICE_NAME]") {
+		url = strings.ReplaceAll(provider.Url, "[SERVICE_NAME]", serviceName)
+	}
+	bodyBuffer := bytes.NewBuffer([]byte(body))
+	request, _ := http.NewRequest(provider.Method, url, bodyBuffer)
+	for k, v := range provider.Headers {
+		request.Header.Set(k, v)
+	}
+	return request
+}
+
+func (provider *CustomAlertProvider) Send(serviceName, alertDescription string) error {
+	request := provider.buildRequest(serviceName, alertDescription)
+	response, err := client.GetHttpClient().Do(request)
+	if err != nil {
+		return err
+	}
+	if response.StatusCode > 399 {
+		return fmt.Errorf("call to provider alert returned status code %d", response.StatusCode)
+	}
+	return nil
+}

core/condition.go

@@ -0,0 +1,51 @@
+package core
+
+import (
+	"fmt"
+	"log"
+	"strings"
+)
+
+type Condition string
+
+func (c *Condition) evaluate(result *Result) bool {
+	condition := string(*c)
+	success := false
+	var resolvedCondition string
+	if strings.Contains(condition, "==") {
+		parts := sanitizeAndResolve(strings.Split(condition, "=="), result)
+		success = parts[0] == parts[1]
+		resolvedCondition = fmt.Sprintf("%v == %v", parts[0], parts[1])
+	} else if strings.Contains(condition, "!=") {
+		parts := sanitizeAndResolve(strings.Split(condition, "!="), result)
+		success = parts[0] != parts[1]
+		resolvedCondition = fmt.Sprintf("%v != %v", parts[0], parts[1])
+	} else if strings.Contains(condition, "<=") {
+		parts := sanitizeAndResolveNumerical(strings.Split(condition, "<="), result)
+		success = parts[0] <= parts[1]
+		resolvedCondition = fmt.Sprintf("%v <= %v", parts[0], parts[1])
+	} else if strings.Contains(condition, ">=") {
+		parts := sanitizeAndResolveNumerical(strings.Split(condition, ">="), result)
+		success = parts[0] >= parts[1]
+		resolvedCondition = fmt.Sprintf("%v >= %v", parts[0], parts[1])
+	} else if strings.Contains(condition, ">") {
+		parts := sanitizeAndResolveNumerical(strings.Split(condition, ">"), result)
+		success = parts[0] > parts[1]
+		resolvedCondition = fmt.Sprintf("%v > %v", parts[0], parts[1])
+	} else if strings.Contains(condition, "<") {
+		parts := sanitizeAndResolveNumerical(strings.Split(condition, "<"), result)
+		success = parts[0] < parts[1]
+		resolvedCondition = fmt.Sprintf("%v < %v", parts[0], parts[1])
+	} else {
+		result.Errors = append(result.Errors, fmt.Sprintf("invalid condition '%s' has been provided", condition))
+		return false
+	}
+	conditionToDisplay := condition
+	// If the condition isn't a success, return what the resolved condition was too
+	if !success {
+		log.Printf("[Condition][evaluate] Condition '%s' did not succeed because '%s' is false", condition, resolvedCondition)
+		conditionToDisplay = fmt.Sprintf("%s (%s)", condition, resolvedCondition)
+	}
+	result.ConditionResults = append(result.ConditionResults, &ConditionResult{Condition: conditionToDisplay, Success: success})
+	return success
+}

core/condition_test.go

@@ -0,0 +1,186 @@
+package core
+
+import (
+	"testing"
+	"time"
+)
+
+func TestCondition_evaluateWithIp(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 TestCondition_evaluateWithStatus(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 TestCondition_evaluateWithStatusFailure(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 TestCondition_evaluateWithStatusUsingLessThan(t *testing.T) {
+	condition := Condition("[STATUS] < 300")
+	result := &Result{HttpStatus: 201}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
+func TestCondition_evaluateWithStatusFailureUsingLessThan(t *testing.T) {
+	condition := Condition("[STATUS] < 300")
+	result := &Result{HttpStatus: 404}
+	condition.evaluate(result)
+	if result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a failure", condition)
+	}
+}
+
+func TestCondition_evaluateWithResponseTimeUsingLessThan(t *testing.T) {
+	condition := Condition("[RESPONSE_TIME] < 500")
+	result := &Result{Duration: time.Millisecond * 50}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
+func TestCondition_evaluateWithResponseTimeUsingGreaterThan(t *testing.T) {
+	condition := Condition("[RESPONSE_TIME] > 500")
+	result := &Result{Duration: time.Millisecond * 750}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
+func TestCondition_evaluateWithResponseTimeUsingGreaterThanOrEqualTo(t *testing.T) {
+	condition := Condition("[RESPONSE_TIME] >= 500")
+	result := &Result{Duration: time.Millisecond * 500}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
+func TestCondition_evaluateWithResponseTimeUsingLessThanOrEqualTo(t *testing.T) {
+	condition := Condition("[RESPONSE_TIME] <= 500")
+	result := &Result{Duration: time.Millisecond * 500}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
+func TestCondition_evaluateWithBody(t *testing.T) {
+	condition := Condition("[BODY] == test")
+	result := &Result{Body: []byte("test")}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
+func TestCondition_evaluateWithBodyJsonPath(t *testing.T) {
+	condition := Condition("[BODY].status == UP")
+	result := &Result{Body: []byte("{\"status\":\"UP\"}")}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
+func TestCondition_evaluateWithBodyJsonPathComplex(t *testing.T) {
+	condition := Condition("[BODY].data.name == john")
+	result := &Result{Body: []byte("{\"data\": {\"id\": 1, \"name\": \"john\"}}")}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
+func TestCondition_evaluateWithBodyJsonPathLongInt(t *testing.T) {
+	condition := Condition("[BODY].data.id == 1")
+	result := &Result{Body: []byte("{\"data\": {\"id\": 1}}")}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
+func TestCondition_evaluateWithBodyJsonPathComplexInt(t *testing.T) {
+	condition := Condition("[BODY].data[1].id == 2")
+	result := &Result{Body: []byte("{\"data\": [{\"id\": 1}, {\"id\": 2}, {\"id\": 3}]}")}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
+func TestCondition_evaluateWithBodyJsonPathComplexIntUsingGreaterThan(t *testing.T) {
+	condition := Condition("[BODY].data.id > 0")
+	result := &Result{Body: []byte("{\"data\": {\"id\": 1}}")}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
+func TestCondition_evaluateWithBodyJsonPathComplexIntFailureUsingGreaterThan(t *testing.T) {
+	condition := Condition("[BODY].data.id > 5")
+	result := &Result{Body: []byte("{\"data\": {\"id\": 1}}")}
+	condition.evaluate(result)
+	if result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a failure", condition)
+	}
+}
+
+func TestCondition_evaluateWithBodyJsonPathComplexIntUsingLessThan(t *testing.T) {
+	condition := Condition("[BODY].data.id < 5")
+	result := &Result{Body: []byte("{\"data\": {\"id\": 2}}")}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
+func TestCondition_evaluateWithBodyJsonPathComplexIntFailureUsingLessThan(t *testing.T) {
+	condition := Condition("[BODY].data.id < 5")
+	result := &Result{Body: []byte("{\"data\": {\"id\": 10}}")}
+	condition.evaluate(result)
+	if result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a failure", condition)
+	}
+}
+
+func TestCondition_evaluateWithBodySliceLength(t *testing.T) {
+	condition := Condition("len([BODY].data) == 3")
+	result := &Result{Body: []byte("{\"data\": [{\"id\": 1}, {\"id\": 2}, {\"id\": 3}]}")}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
+func TestCondition_evaluateWithBodyStringLength(t *testing.T) {
+	condition := Condition("len([BODY].name) == 8")
+	result := &Result{Body: []byte("{\"name\": \"john.doe\"}")}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}

core/service.go

@@ -0,0 +1,150 @@
+package core
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"github.com/TwinProduction/gatus/client"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"net/url"
+	"time"
+)
+
+var (
+	ErrNoCondition = errors.New("you must specify at least one condition per service")
+	ErrNoUrl       = errors.New("you must specify an url for each service")
+)
+
+type Service struct {
+	Name       string            `yaml:"name"`
+	Url        string            `yaml:"url"`
+	Method     string            `yaml:"method,omitempty"`
+	Body       string            `yaml:"body,omitempty"`
+	GraphQL    bool              `yaml:"graphql,omitempty"`
+	Headers    map[string]string `yaml:"headers,omitempty"`
+	Interval   time.Duration     `yaml:"interval,omitempty"`
+	Conditions []*Condition      `yaml:"conditions"`
+	Alerts     []*Alert          `yaml:"alerts"`
+
+	numberOfFailuresInARow int
+}
+
+func (service *Service) Validate() {
+	// Set default values
+	if service.Interval == 0 {
+		service.Interval = 10 * time.Second
+	}
+	if len(service.Method) == 0 {
+		service.Method = http.MethodGet
+	}
+	if len(service.Headers) == 0 {
+		service.Headers = make(map[string]string)
+	}
+	for _, alert := range service.Alerts {
+		if alert.Threshold <= 0 {
+			alert.Threshold = 3
+		}
+	}
+	if len(service.Url) == 0 {
+		panic(ErrNoUrl)
+	}
+	if len(service.Conditions) == 0 {
+		panic(ErrNoCondition)
+	}
+
+	// Make sure that the request can be created
+	_, err := http.NewRequest(service.Method, service.Url, bytes.NewBuffer([]byte(service.Body)))
+	if err != nil {
+		panic(err)
+	}
+}
+
+func (service *Service) EvaluateConditions() *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()
+	if result.Success {
+		service.numberOfFailuresInARow = 0
+		// TODO: Send notification that alert has been resolved?
+	} else {
+		service.numberOfFailuresInARow++
+	}
+	return result
+}
+
+func (service *Service) GetAlertsTriggered() []Alert {
+	var alerts []Alert
+	if service.numberOfFailuresInARow == 0 {
+		return alerts
+	}
+	for _, alert := range service.Alerts {
+		if alert.Enabled && alert.Threshold == service.numberOfFailuresInARow {
+			alerts = append(alerts, *alert)
+			continue
+		}
+	}
+	return alerts
+}
+
+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) call(result *Result) {
+	request := service.buildRequest()
+	startTime := time.Now()
+	response, err := client.GetHttpClient().Do(request)
+	if err != nil {
+		result.Duration = time.Since(startTime)
+		result.Errors = append(result.Errors, err.Error())
+		return
+	}
+	result.Duration = time.Since(startTime)
+	result.HttpStatus = response.StatusCode
+	result.Body, err = ioutil.ReadAll(response.Body)
+	if err != nil {
+		result.Errors = append(result.Errors, err.Error())
+	}
+}
+
+func (service *Service) buildRequest() *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)
+	}
+	return request
+}

core/service_test.go

@@ -0,0 +1,37 @@
+package core
+
+import (
+	"testing"
+)
+
+func TestIntegrationEvaluateConditions(t *testing.T) {
+	condition := Condition("[STATUS] == 200")
+	service := Service{
+		Name:       "TwiNNatioN",
+		Url:        "https://twinnation.org/health",
+		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:       "TwiNNatioN",
+		Url:        "https://twinnation.org/health",
+		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/types.go

@@ -1,12 +1,6 @@
 package core
 
 import (
-	"fmt"
-	"net"
-	"net/http"
-	"net/url"
-	"strconv"
-	"strings"
 	"time"
 )
 
@@ -15,15 +9,11 @@ type HealthStatus struct {
 	Message string `json:"message,omitempty"`
 }
 
-type ServerMessage struct {
-	Error   bool   `json:"error"`
-	Message string `json:"message"`
-}
-
 type Result struct {
 	HttpStatus       int                `json:"status"`
+	Body             []byte             `json:"-"`
 	Hostname         string             `json:"hostname"`
-	Ip               string             `json:"ip"`
+	Ip               string             `json:"-"`
 	Duration         time.Duration      `json:"duration"`
 	Errors           []string           `json:"errors"`
 	ConditionResults []*ConditionResult `json:"condition-results"`
@@ -31,122 +21,7 @@ type Result struct {
 	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
+	Condition string `json:"condition"`
+	Success   bool   `json:"success"`
 }

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/util.go

@@ -0,0 +1,74 @@
+package core
+
+import (
+	"fmt"
+	"github.com/TwinProduction/gatus/jsonpath"
+	"strconv"
+	"strings"
+)
+
+const (
+	StatusPlaceholder       = "[STATUS]"
+	IPPlaceHolder           = "[IP]"
+	ResponseTimePlaceHolder = "[RESPONSE_TIME]"
+	BodyPlaceHolder         = "[BODY]"
+
+	LengthFunctionPrefix = "len("
+	FunctionSuffix       = ")"
+
+	InvalidConditionElementSuffix = "(INVALID)"
+)
+
+func sanitizeAndResolve(list []string, result *Result) []string {
+	var sanitizedList []string
+	body := strings.TrimSpace(string(result.Body))
+	for _, element := range list {
+		element = strings.TrimSpace(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
+		default:
+			// if starts with BodyPlaceHolder, then evaluate json path
+			if strings.Contains(element, BodyPlaceHolder) {
+				wantLength := false
+				if strings.HasPrefix(element, LengthFunctionPrefix) && strings.HasSuffix(element, FunctionSuffix) {
+					wantLength = true
+					element = strings.TrimSuffix(strings.TrimPrefix(element, LengthFunctionPrefix), FunctionSuffix)
+				}
+				resolvedElement, resolvedElementLength, err := jsonpath.Eval(strings.Replace(element, fmt.Sprintf("%s.", BodyPlaceHolder), "", 1), result.Body)
+				if err != nil {
+					result.Errors = append(result.Errors, err.Error())
+					element = fmt.Sprintf("%s %s", element, InvalidConditionElementSuffix)
+				} else {
+					if wantLength {
+						element = fmt.Sprintf("%d", resolvedElementLength)
+					} else {
+						element = resolvedElement
+					}
+				}
+			}
+		}
+		sanitizedList = append(sanitizedList, element)
+	}
+	return sanitizedList
+}
+
+func sanitizeAndResolveNumerical(list []string, result *Result) []int {
+	var sanitizedNumbers []int
+	sanitizedList := sanitizeAndResolve(list, result)
+	for _, element := range sanitizedList {
+		if number, err := strconv.Atoi(element); err != nil {
+			// Default to 0 if the string couldn't be converted to an integer
+			sanitizedNumbers = append(sanitizedNumbers, 0)
+		} else {
+			sanitizedNumbers = append(sanitizedNumbers, number)
+		}
+	}
+	return sanitizedNumbers
+}

example/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

example/kubernetes/gatus.yaml

@@ -4,12 +4,13 @@ data:
     metrics: true
     services:
       - name: TwiNNatioN
-        url: https://twinnation.org/actuator/health
+        url: https://twinnation.org/health
         interval: 1m
         conditions:
           - "[STATUS] == 200"
       - name: GitHub
         url: https://api.github.com/healthz
+        interval: 5m
         conditions:
           - "[STATUS] == 200"
       - name: Example

go.mod

@@ -1,6 +1,6 @@
 module github.com/TwinProduction/gatus
 
-go 1.13
+go 1.15
 
 require (
 	github.com/prometheus/client_golang v1.2.1

jsonpath/jsonpath.go

@@ -0,0 +1,74 @@
+package jsonpath
+
+import (
+	"encoding/json"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// Eval is a half-baked json path implementation that needs some love
+func Eval(path string, b []byte) (string, int, error) {
+	var object interface{}
+	err := json.Unmarshal(b, &object)
+	if err != nil {
+		// Try to unmarshal it into an array instead
+		return "", 0, err
+	}
+	return walk(path, object)
+}
+
+func walk(path string, object interface{}) (string, int, error) {
+	keys := strings.Split(path, ".")
+	currentKey := keys[0]
+	switch value := extractValue(currentKey, object).(type) {
+	case map[string]interface{}:
+		return walk(strings.Replace(path, fmt.Sprintf("%s.", currentKey), "", 1), value)
+	case string:
+		return value, len(value), nil
+	case []interface{}:
+		return fmt.Sprintf("%v", value), len(value), nil
+	case interface{}:
+		return fmt.Sprintf("%v", value), 1, nil
+	default:
+		return "", 0, fmt.Errorf("couldn't walk through '%s' because type was '%T', but expected 'map[string]interface{}'", currentKey, value)
+	}
+}
+
+func extractValue(currentKey string, value interface{}) interface{} {
+	// Check if the current key ends with [#]
+	if strings.HasSuffix(currentKey, "]") && strings.Contains(currentKey, "[") {
+		tmp := strings.SplitN(currentKey, "[", 3)
+		arrayIndex, err := strconv.Atoi(strings.Replace(tmp[1], "]", "", 1))
+		if err != nil {
+			return value
+		}
+		currentKey := tmp[0]
+		// if currentKey contains only an index (i.e. [0] or 0)
+		if len(currentKey) == 0 {
+			array := value.([]interface{})
+			if len(array) > arrayIndex {
+				if len(tmp) > 2 {
+					// Nested array? Go deeper.
+					return extractValue(fmt.Sprintf("%s[%s", currentKey, tmp[2]), array[arrayIndex])
+				}
+				return array[arrayIndex]
+			}
+			return nil
+		}
+		if value == nil || value.(map[string]interface{})[currentKey] == nil {
+			return nil
+		}
+		// if currentKey contains both a key and an index (i.e. data[0])
+		array := value.(map[string]interface{})[currentKey].([]interface{})
+		if len(array) > arrayIndex {
+			if len(tmp) > 2 {
+				// Nested array? Go deeper.
+				return extractValue(fmt.Sprintf("[%s", tmp[2]), array[arrayIndex])
+			}
+			return array[arrayIndex]
+		}
+		return nil
+	}
+	return value.(map[string]interface{})[currentKey]
+}

jsonpath/jsonpath_test.go

@@ -0,0 +1,152 @@
+package jsonpath
+
+import "testing"
+
+func TestEval(t *testing.T) {
+	path := "simple"
+	data := `{"simple": "value"}`
+
+	expectedOutput := "value"
+
+	output, outputLength, err := Eval(path, []byte(data))
+	if err != nil {
+		t.Error("Didn't expect any error, but got", err)
+	}
+	if outputLength != len(expectedOutput) {
+		t.Errorf("Expected output length to be %v, but was %v", len(expectedOutput), outputLength)
+	}
+	if output != expectedOutput {
+		t.Errorf("Expected output to be %v, but was %v", expectedOutput, output)
+	}
+}
+
+func TestEvalWithLongSimpleWalk(t *testing.T) {
+	path := "long.simple.walk"
+	data := `{"long": {"simple": {"walk": "value"}}}`
+
+	expectedOutput := "value"
+
+	output, _, err := Eval(path, []byte(data))
+	if err != nil {
+		t.Error("Didn't expect any error, but got", err)
+	}
+	if output != expectedOutput {
+		t.Errorf("Expected output to be %v, but was %v", expectedOutput, output)
+	}
+}
+
+func TestEvalWithArrayOfMaps(t *testing.T) {
+	path := "ids[1].id"
+	data := `{"ids": [{"id": 1}, {"id": 2}]}`
+
+	expectedOutput := "2"
+
+	output, _, err := Eval(path, []byte(data))
+	if err != nil {
+		t.Error("Didn't expect any error, but got", err)
+	}
+
+	if output != expectedOutput {
+		t.Errorf("Expected output to be %v, but was %v", expectedOutput, output)
+	}
+}
+
+func TestEvalWithArrayOfValues(t *testing.T) {
+	path := "ids[0]"
+	data := `{"ids": [1, 2]}`
+
+	expectedOutput := "1"
+
+	output, _, err := Eval(path, []byte(data))
+	if err != nil {
+		t.Error("Didn't expect any error, but got", err)
+	}
+	if output != expectedOutput {
+		t.Errorf("Expected output to be %v, but was %v", expectedOutput, output)
+	}
+}
+
+func TestEvalWithRootArrayOfValues(t *testing.T) {
+	path := "[1]"
+	data := `[1, 2]`
+
+	expectedOutput := "2"
+
+	output, _, err := Eval(path, []byte(data))
+	if err != nil {
+		t.Error("Didn't expect any error, but got", err)
+	}
+	if output != expectedOutput {
+		t.Errorf("Expected output to be %v, but was %v", expectedOutput, output)
+	}
+}
+
+func TestEvalWithRootArrayOfMaps(t *testing.T) {
+	path := "[0].id"
+	data := `[{"id": 1}, {"id": 2}]`
+
+	expectedOutput := "1"
+
+	output, _, err := Eval(path, []byte(data))
+	if err != nil {
+		t.Error("Didn't expect any error, but got", err)
+	}
+	if output != expectedOutput {
+		t.Errorf("Expected output to be %v, but was %v", expectedOutput, output)
+	}
+}
+
+func TestEvalWithRootArrayOfMapsUsingInvalidArrayIndex(t *testing.T) {
+	path := "[5].id"
+	data := `[{"id": 1}, {"id": 2}]`
+
+	_, _, err := Eval(path, []byte(data))
+	if err == nil {
+		t.Error("Should've returned an error, but didn't")
+	}
+}
+
+func TestEvalWithLongWalkAndArray(t *testing.T) {
+	path := "data.ids[0].id"
+	data := `{"data": {"ids": [{"id": 1}, {"id": 2}, {"id": 3}]}}`
+
+	expectedOutput := "1"
+
+	output, _, err := Eval(path, []byte(data))
+	if err != nil {
+		t.Error("Didn't expect any error, but got", err)
+	}
+	if output != expectedOutput {
+		t.Errorf("Expected output to be %v, but was %v", expectedOutput, output)
+	}
+}
+
+func TestEvalWithNestedArray(t *testing.T) {
+	path := "[3][2]"
+	data := `[[1, 2], [3, 4], [], [5, 6, 7]]`
+
+	expectedOutput := "7"
+
+	output, _, err := Eval(path, []byte(data))
+	if err != nil {
+		t.Error("Didn't expect any error, but got", err)
+	}
+	if output != expectedOutput {
+		t.Errorf("Expected output to be %v, but was %v", expectedOutput, output)
+	}
+}
+
+func TestEvalWithMapOfNestedArray(t *testing.T) {
+	path := "data[1][1]"
+	data := `{"data": [["a", "b", "c"], ["d", "e", "f"]]}`
+
+	expectedOutput := "e"
+
+	output, _, err := Eval(path, []byte(data))
+	if err != nil {
+		t.Error("Didn't expect any error, but got", err)
+	}
+	if output != expectedOutput {
+		t.Errorf("Expected output to be %v, but was %v", expectedOutput, output)
+	}
+}

main.go

@@ -1,19 +1,29 @@
 package main
 
 import (
+	"bytes"
+	"compress/gzip"
 	"encoding/json"
 	"github.com/TwinProduction/gatus/config"
-	"github.com/TwinProduction/gatus/core"
 	"github.com/TwinProduction/gatus/watchdog"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"log"
 	"net/http"
 	"os"
+	"strings"
+	"time"
+)
+
+const CacheTTL = 10 * time.Second
+
+var (
+	cachedServiceResults          []byte
+	cachedServiceResultsGzipped   []byte
+	cachedServiceResultsTimestamp time.Time
 )
 
 func main() {
 	cfg := loadConfiguration()
-	go watchdog.Monitor(cfg)
 	http.HandleFunc("/api/v1/results", serviceResultsHandler)
 	http.HandleFunc("/health", healthHandler)
 	http.Handle("/", http.FileServer(http.Dir("./static")))
@@ -21,14 +31,15 @@ func main() {
 		http.Handle("/metrics", promhttp.Handler())
 	}
 	log.Println("[main][main] Listening on port 8080")
+	go watchdog.Monitor(cfg)
 	log.Fatal(http.ListenAndServe(":8080", nil))
 }
 
 func loadConfiguration() *config.Config {
-	args := os.Args
 	var err error
-	if len(args) == 2 {
-		err = config.Load(args[1])
+	customConfigFile := os.Getenv("GATUS_CONFIG_FILE")
+	if len(customConfigFile) > 0 {
+		err = config.Load(customConfigFile)
 	} else {
 		err = config.LoadDefaultConfiguration()
 	}
@@ -38,23 +49,38 @@ func loadConfiguration() *config.Config {
 	return config.Get()
 }
 
-func serviceResultsHandler(writer http.ResponseWriter, _ *http.Request) {
-	serviceResults := watchdog.GetServiceResults()
+func serviceResultsHandler(writer http.ResponseWriter, r *http.Request) {
+	if isExpired := cachedServiceResultsTimestamp.IsZero() || time.Now().Sub(cachedServiceResultsTimestamp) > CacheTTL; isExpired {
+		buffer := &bytes.Buffer{}
+		gzipWriter := gzip.NewWriter(buffer)
+		serviceResults := watchdog.GetServiceResults()
+		data, err := json.Marshal(serviceResults)
+		if err != nil {
+			log.Printf("[main][serviceResultsHandler] Unable to marshall object to JSON: %s", err.Error())
+			writer.WriteHeader(http.StatusInternalServerError)
+			_, _ = writer.Write([]byte("Unable to marshall object to JSON"))
+			return
+		}
+		gzipWriter.Write(data)
+		gzipWriter.Close()
+		cachedServiceResults = data
+		cachedServiceResultsGzipped = buffer.Bytes()
+		cachedServiceResultsTimestamp = time.Now()
+	}
+	var data []byte
+	if strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
+		writer.Header().Set("Content-Encoding", "gzip")
+		data = cachedServiceResultsGzipped
+	} else {
+		data = cachedServiceResults
+	}
 	writer.Header().Add("Content-type", "application/json")
 	writer.WriteHeader(http.StatusOK)
-	_, _ = writer.Write(structToJsonBytes(serviceResults))
+	_, _ = writer.Write(data)
 }
 
 func healthHandler(writer http.ResponseWriter, _ *http.Request) {
 	writer.Header().Add("Content-type", "application/json")
 	writer.WriteHeader(http.StatusOK)
-	_, _ = writer.Write(structToJsonBytes(&core.HealthStatus{Status: "UP"}))
-}
-
-func structToJsonBytes(obj interface{}) []byte {
-	bytes, err := json.Marshal(obj)
-	if err != nil {
-		log.Printf("[main][structToJsonBytes] Unable to marshall object to JSON: %s", err.Error())
-	}
-	return bytes
+	_, _ = writer.Write([]byte("{\"status\":\"UP\"}"))
 }

static/index.html

@@ -1,103 +1,288 @@
 <!DOCTYPE html>
 <html lang="en">
 <head>
-	<title>Status</title>
+	<title>Health Dashboard</title>
+	<meta name="viewport" content="width=device-width, initial-scale=1" />
 	<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
 	<style>
-		td > span.badge {
+		html, body {
+			background-color: #f7f9fb;
+		}
+		html {
+			height: 100%;
+		}
+		#results div.container:first-child {
+			border-top-left-radius: 3px;
+			border-top-right-radius: 3px;
+		}
+		#results div.container:last-child {
+			border-bottom-left-radius: 3px;
+			border-bottom-right-radius: 3px;
+			border-bottom-width: 1px;
+			border-color: #dee2e6;
+			border-style: solid;
+		}
+		.status-ok {
 			display: inline-block;
-			width: 20px;
-			cursor: default;
-			margin-right: 2px;
+			width: 1%;
+			height: 20px;
+			margin-right: 4px;
+			background-color: #28a745;
+		}
+		.status {
+			cursor: pointer;
+			transition: all 500ms ease-in-out;
+			overflow-x: hidden;
+			padding: .25em 0;
+			color: white;
+		}
+		.title {
+			font-size: 2.5rem;
+		}
+		.status:hover {
+			opacity: 0.7;
+			transition: opacity 100ms ease-in-out;
+			color: black;
+		}
+		.status-over-time {
+			overflow: auto;
+		}
+		.status-over-time>span:not(:last-child) {
+			margin-left: 2px;
+		}
+		.status-time-ago {
+			color: #6a737d;
+			opacity: 0.5;
+			margin-top: 5px;
+		}
+		.status-min-max-ms {
+			overflow-x: hidden;
+		}
+		#tooltip {
+			position: fixed;
+			top: 0;
+			left: 0;
+			background-color: white;
+			border: 1px solid lightgray;
+			border-radius: 4px;
+			padding: 6px;
+			font-size: 13px;
+		}
+		#tooltip code {
+			color: #212529;
+			line-height: 1;
+		}
+		#tooltip .tooltip-title {
+			font-weight: bold;
+			margin-bottom: 0;
+			display: block;
+		}
+		#tooltip .tooltip-title {
+			margin-top: 8px;
+		}
+		#tooltip>.tooltip-title:first-child {
+			margin-top: 0;
 		}
 	</style>
 </head>
 <body>
-	<div class="container my-3 bg-light rounded p-4 border shadow">
-		<div class="text-center mb-3">
-			<div class="display-4">Status</div>
+	<div class="container my-3 rounded p-3 border shadow">
+		<div class="mb-2">
+			<div class="row">
+				<div class="col-8 text-left my-auto">
+					<div class="title display-4">Health Status</div>
+				</div>
+				<div class="col-4 text-right">
+					<img src="logo.png" alt="GaTuS" style="position: relative; min-width: 50px; max-width: 200px; width: 20%;"/>
+				</div>
+			</div>
 		</div>
-		<div class="table-responsive">
-			<table class="table">
-				<thead>
-					<tr>
-						<th scope="col">Name</th>
-						<th scope="col">Status</th>
-						<th scope="col">Hostname</th>
-						<th scope="col">Response time</th>
-					</tr>
-				</thead>
-				<tbody id="results">
-				</tbody>
-			</table>
+		<div id="results"></div>
+	</div>
+
+	<div id="tooltip" style="display: none">
+		<div class="tooltip-title">Timestamp:</div>
+		<code id="tooltip-timestamp">...</code>
+		<div class="tooltip-title">Response time:</div>
+		<code id="tooltip-response-time">...</code>
+		<div class="tooltip-title">Conditions:</div>
+		<code id="tooltip-conditions">...</code>
+		<div id="tooltip-errors-container">
+			<div class="tooltip-title">Errors:</div>
+			<code id="tooltip-errors">...</code>
 		</div>
 	</div>
 
 	<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
-	<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" integrity="sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQq4sF86dIHNDz0W1" crossorigin="anonymous"></script>
 	<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>
 
 	<script>
-		const OK = "<span class='badge badge-success' title='__RESPONSE_TIME____CONDITIONS____ERRORS__'>&#10003;</span>";
-		const NOK = "<span class='badge badge-danger' title='__RESPONSE_TIME____CONDITIONS____ERRORS__'>X</span>";
+		let serviceStatuses = {};
+		let timerHandler = 0;
+		let userClickedStatus = false;
 
-		function generateServiceResultBox(serviceResult) {
-			let output = (serviceResult.success ? OK : NOK);
-			output = output.replace("__RESPONSE_TIME__", "Response time:\n" + parseInt(serviceResult.duration/1000000) + "ms");
+		function showTooltip(serviceName, index, element) {
+			userClickedStatus = false;
+			clearTimeout(timerHandler);
+			let serviceResult = serviceStatuses[serviceName][index];
+			$("#tooltip-timestamp").text(prettifyTimestamp(serviceResult.timestamp));
+			$("#tooltip-response-time").text(parseInt(serviceResult.duration/1000000) + "ms");
+			// Populate the condition section
 			let conditions = "";
-			for (let conditionResultIndex in serviceResult['condition-results']) {
-				let conditionResult = serviceResult['condition-results'][conditionResultIndex];
-				conditions += "\n- " + (conditionResult.success ? "&#10003;" : "X") + " ~ " + conditionResult.condition;
+			for (let i in serviceResult['condition-results']) {
+				let conditionResult = serviceResult['condition-results'][i];
+				conditions += (conditionResult.success ? "&#10003;" : "X") + " ~ " + htmlEntities(conditionResult.condition) + "<br />";
 			}
-			output = output.replace("__CONDITIONS__", "\n\nConditions:" + conditions);
-			if (serviceResult['errors'].length > 0) {
+			$("#tooltip-conditions").html(conditions);
+			// Populate the error section only if there are errors
+			if (serviceResult.errors && serviceResult.errors.length > 0) {
 				let errors = "";
-				for (let errorIndex in serviceResult['errors']) {
-					errors += "\n- " + serviceResult['errors'][errorIndex];
+				for (let i in serviceResult.errors) {
+					errors += "- " + htmlEntities(serviceResult.errors[i]) + "<br />";
 				}
-				output = output.replace("__ERRORS__", "\n\nErrors: " + errors);
+				$("#tooltip-errors").html(errors);
+				$("#tooltip-errors-container").show();
 			} else {
-				output = output.replace("__ERRORS__", "");
+				$("#tooltip-errors-container").hide();
 			}
-			return output;
-		}
-		
-		function refreshTable() {
-			$.getJSON("/api/v1/results", function (data) {
-				let tableBody = "";
-				for (let serviceName in data) {
-					let serviceStatusOverTime = "";
-					let hostname = data[serviceName][data[serviceName].length-1].hostname 
-					let minResponseTime = null;
-					let maxResponseTime = null;
-					for (let key in data[serviceName]) {
-						let serviceResult = data[serviceName][key];
-						console.log(serviceResult);
-						serviceStatusOverTime = generateServiceResultBox(serviceResult) + serviceStatusOverTime;
-						const responseTime = parseInt(serviceResult.duration/1000000);
-						if (minResponseTime == null || minResponseTime > responseTime) {
-							minResponseTime = responseTime;
-						}
-						if (maxResponseTime == null || maxResponseTime < responseTime) {
-							maxResponseTime = responseTime;
-						}
-					}
-					tableBody += ""
-						+ "<tr>"
-						+ "  <td>" + serviceName + "</td>"
-						+ "  <td>" + serviceStatusOverTime + "</td>"
-						+ "  <td><a href=\"//" + hostname + "\">" + hostname + "</a></td>"
-						+ "  <td>" + (minResponseTime === maxResponseTime ? minResponseTime : (minResponseTime + "-" + maxResponseTime)) + "ms</td>"
-						+ "</tr>";
+			// Position tooltip
+			$("#tooltip").css({top: "0px", left: "0px"}).show();
+			let targetTopPosition = element.getBoundingClientRect().y + 30;
+			let targetLeftPosition = element.getBoundingClientRect().x;
+			// Make adjustments if necessary
+			let tooltipBoundingClientRect = document.querySelector('#tooltip').getBoundingClientRect();
+			if (targetLeftPosition + window.scrollX + tooltipBoundingClientRect.width + 50 > document.body.getBoundingClientRect().width) {
+				targetLeftPosition = element.getBoundingClientRect().x - tooltipBoundingClientRect.width + element.getBoundingClientRect().width;
+				if (targetLeftPosition < 0) {
+					targetLeftPosition += -targetLeftPosition;
+				}
+			}
+			if (targetTopPosition + window.scrollY + tooltipBoundingClientRect.height + 50 > document.body.getBoundingClientRect().height && targetTopPosition >= 0) {
+				targetTopPosition = element.getBoundingClientRect().y - (tooltipBoundingClientRect.height + 10);
+				if (targetTopPosition < 0) {
+					targetTopPosition = element.getBoundingClientRect().y + 30;
+				}
+			}
+			$("#tooltip").css({top: targetTopPosition + "px", left: targetLeftPosition + "px"});
+		}
+
+		function fadeTooltip() {
+			if (!userClickedStatus) {
+				timerHandler = setTimeout(function () {
+					$("#tooltip").hide();
+				}, 500);
+			}
+		}
+
+		function createStatusBadge(serviceName, index, success) {
+			if (success) {
+				return "<span class='status badge badge-success' style='width: 5%' onmouseenter='showTooltip(\""+serviceName+"\", "+index+", this)' onmouseleave='fadeTooltip()' onclick='userClickedStatus = !userClickedStatus;'>&#10003;</span>";
+			}
+			return "<span class='status badge badge-danger' style='width: 5%' onmouseenter='showTooltip(\""+serviceName+"\", "+index+", this)' onmouseleave='fadeTooltip()' onclick='userClickedStatus = !userClickedStatus;'>X</span>";
+		}
+
+		function refreshResults() {
+			$.getJSON("/api/v1/results", function (data) {
+				// Update the table only if there's a change
+				if (JSON.stringify(serviceStatuses) !== JSON.stringify(data)) {
+					serviceStatuses = data;
+					buildTable();
 				}
-				$("#results").html(tableBody);
 			});
 		}
 
-		refreshTable();
+		function buildTable() {
+			let output = "";
+			for (let serviceName in serviceStatuses) {
+				let serviceStatusOverTime = "";
+				let hostname = serviceStatuses[serviceName][serviceStatuses[serviceName].length-1].hostname
+				let minResponseTime = null;
+				let maxResponseTime = null;
+				let newestTimestamp = null;
+				let oldestTimestamp = null;
+				for (let key in serviceStatuses[serviceName]) {
+					let serviceResult = serviceStatuses[serviceName][key];
+					serviceStatusOverTime = createStatusBadge(serviceName, key, serviceResult.success) + serviceStatusOverTime;
+					const responseTime = parseInt(serviceResult.duration/1000000);
+					if (minResponseTime == null || minResponseTime > responseTime) {
+						minResponseTime = responseTime;
+					}
+					if (maxResponseTime == null || maxResponseTime < responseTime) {
+						maxResponseTime = responseTime;
+					}
+					const timestamp = new Date(serviceResult.timestamp);
+					if (newestTimestamp == null || newestTimestamp < timestamp) {
+						newestTimestamp = timestamp;
+					}
+					if (oldestTimestamp == null || oldestTimestamp > timestamp) {
+						oldestTimestamp = timestamp;
+					}
+				}
+				output += ""
+					+ "<div class='container py-3 border-left border-right border-top border-black'>"
+					+ "  <div class='row mb-2'>"
+					+ "    <div class='col-md-10'>"
+					+ "      <span class='font-weight-bold'>" + serviceName + "</span> <span class='text-secondary font-weight-lighter'>- " + hostname + "</span>"
+					+ "    </div>"
+					+ "    <div class='col-md-2 text-right'>"
+					+ "      <span class='font-weight-lighter status-min-max-ms'>" + (minResponseTime === maxResponseTime ? minResponseTime : (minResponseTime + "-" + maxResponseTime)) + "ms</span>"
+					+ "    </div>"
+					+ "  </div>"
+					+ "  <div class='row'>"
+					+ "    <div class='col-12 d-flex flex-row-reverse status-over-time'>"
+					+ "      " + serviceStatusOverTime
+					+ "    </div>"
+					+ "  </div>"
+					+ "  <div class='row status-time-ago'>"
+					+ "    <div class='col-6'>"
+					+ "      " + generatePrettyTimeAgo(oldestTimestamp)
+					+ "    </div>"
+					+ "    <div class='col-6 text-right'>"
+					+ "      " + generatePrettyTimeAgo(newestTimestamp)
+					+ "    </div>"
+					+ "  </div>"
+					+ "</div>";
+			}
+			$("#results").html(output);
+		}
+
+		function prettifyTimestamp(timestamp) {
+			let date = new Date(timestamp);
+			let YYYY = date.getFullYear();
+			let MM = ((date.getMonth()+1)<10?"0":"")+""+(date.getMonth()+1);
+			let DD = ((date.getDate())<10?"0":"")+""+(date.getDate());
+			let hh = ((date.getHours())<10?"0":"")+""+(date.getHours());
+			let mm = ((date.getMinutes())<10?"0":"")+""+(date.getMinutes());
+			let ss = ((date.getSeconds())<10?"0":"")+""+(date.getSeconds());
+			return YYYY + "-" + MM + "-" + DD + " " + hh + ":" + mm + ":" + ss;
+		}
+
+		function generatePrettyTimeAgo(t) {
+			let differenceInMs = new Date().getTime() - new Date(t).getTime();
+			if (differenceInMs > 3600000) {
+				let hours = (differenceInMs/3600000).toFixed(0);
+				return hours + " hour" + (hours !== "1" ? "s" : "") + " ago";
+			}
+			if (differenceInMs > 60000) {
+				let minutes = (differenceInMs/60000).toFixed(0);
+				return minutes + " minute" + (minutes !== "1" ? "s" : "") + " ago";
+			}
+			return (differenceInMs/1000).toFixed(0) + " seconds ago";
+		}
+
+		function htmlEntities(s) {
+			return String(s)
+				.replace(/&/g, '&amp;')
+				.replace(/</g, '&lt;')
+				.replace(/>/g, '&gt;')
+				.replace(/"/g, '&quot;')
+				.replace(/'/g, '&apos;');
+		}
+
+		refreshResults();
 		setInterval(function() {
-			refreshTable();
-		}, 10000);
+			refreshResults();
+		}, 30000);
 	</script>
 </body>
 </html>

vendor/modules.txt

@@ -7,6 +7,7 @@ github.com/golang/protobuf/proto
 # github.com/matttproud/golang_protobuf_extensions v1.0.1
 github.com/matttproud/golang_protobuf_extensions/pbutil
 # github.com/prometheus/client_golang v1.2.1
+## explicit
 github.com/prometheus/client_golang/prometheus
 github.com/prometheus/client_golang/prometheus/internal
 github.com/prometheus/client_golang/prometheus/promauto
@@ -24,4 +25,5 @@ github.com/prometheus/procfs/internal/util
 # golang.org/x/sys v0.0.0-20191010194322-b09406accb47
 golang.org/x/sys/windows
 # gopkg.in/yaml.v2 v2.2.2
+## explicit
 gopkg.in/yaml.v2

watchdog/watchdog.go

@@ -1,6 +1,7 @@
 package watchdog
 
 import (
+	"fmt"
 	"github.com/TwinProduction/gatus/config"
 	"github.com/TwinProduction/gatus/core"
 	"github.com/TwinProduction/gatus/metric"
@@ -14,34 +15,85 @@ var (
 	rwLock         sync.RWMutex
 )
 
+// GetServiceResults returns a list of the last 20 results for each services
 func GetServiceResults() *map[string][]*core.Result {
 	return &serviceResults
 }
 
+// Monitor loops over each services and starts a goroutine to monitor each services separately
 func Monitor(cfg *config.Config) {
 	for _, service := range cfg.Services {
-		go func(service *core.Service) {
-			for {
-				log.Printf("[watchdog][Monitor] Monitoring serviceName=%s", service.Name)
-				result := service.EvaluateConditions()
-				metric.PublishMetricsForService(service, result)
-				rwLock.Lock()
-				serviceResults[service.Name] = append(serviceResults[service.Name], result)
-				if len(serviceResults[service.Name]) > 10 {
-					serviceResults[service.Name] = serviceResults[service.Name][1:]
-				}
-				rwLock.Unlock()
-				log.Printf(
-					"[watchdog][Monitor] Finished monitoring serviceName=%s; errors=%d; requestDuration=%s",
-					service.Name,
-					len(result.Errors),
-					result.Duration.Round(time.Millisecond),
-				)
-				log.Printf("[watchdog][Monitor] Waiting interval=%s before monitoring serviceName=%s", service.Interval, service.Name)
-				time.Sleep(service.Interval)
-			}
-		}(service)
-		// To prevent multiple requests from running exactly at the same time
-		time.Sleep(100 * time.Millisecond)
+		go monitor(service)
+		// To prevent multiple requests from running at the same time
+		time.Sleep(1111 * time.Millisecond)
+	}
+}
+
+// monitor monitors a single service in a loop
+func monitor(service *core.Service) {
+	for {
+		// By placing the lock here, we prevent multiple services from being monitored at the exact same time, which
+		// could cause performance issues and return inaccurate results
+		rwLock.Lock()
+		log.Printf("[watchdog][monitor] Monitoring serviceName=%s", service.Name)
+		result := service.EvaluateConditions()
+		metric.PublishMetricsForService(service, result)
+		serviceResults[service.Name] = append(serviceResults[service.Name], result)
+		if len(serviceResults[service.Name]) > 20 {
+			serviceResults[service.Name] = serviceResults[service.Name][1:]
+		}
+		rwLock.Unlock()
+		var extra string
+		if !result.Success {
+			extra = fmt.Sprintf("responseBody=%s", result.Body)
+		}
+		log.Printf(
+			"[watchdog][monitor] Finished monitoring serviceName=%s; errors=%d; requestDuration=%s; %s",
+			service.Name,
+			len(result.Errors),
+			result.Duration.Round(time.Millisecond),
+			extra,
+		)
+
+		cfg := config.Get()
+		if cfg.Alerting != nil {
+			for _, alertTriggered := range service.GetAlertsTriggered() {
+				var alertProvider *core.CustomAlertProvider
+				if alertTriggered.Type == core.SlackAlert {
+					if len(cfg.Alerting.Slack) > 0 {
+						log.Printf("[watchdog][monitor] Sending Slack alert because alert with description=%s has been triggered", alertTriggered.Description)
+						alertProvider = &core.CustomAlertProvider{
+							Url:     cfg.Alerting.Slack,
+							Method:  "POST",
+							Body:    fmt.Sprintf(`{"text":"*[Gatus]*\n*service:* %s\n*description:* %s"}`, service.Name, alertTriggered.Description),
+							Headers: map[string]string{"Content-Type": "application/json"},
+						}
+					} else {
+						log.Printf("[watchdog][monitor] Not sending Slack alert despite being triggered, because there is no Slack webhook configured")
+					}
+				} else if alertTriggered.Type == core.CustomAlert {
+					if cfg.Alerting.Custom != nil && len(cfg.Alerting.Custom.Url) > 0 {
+						log.Printf("[watchdog][monitor] Sending custom alert because alert with description=%s has been triggered", alertTriggered.Description)
+						alertProvider = &core.CustomAlertProvider{
+							Url:     cfg.Alerting.Custom.Url,
+							Method:  cfg.Alerting.Custom.Method,
+							Body:    cfg.Alerting.Custom.Body,
+							Headers: cfg.Alerting.Custom.Headers,
+						}
+					} else {
+						log.Printf("[watchdog][monitor] Not sending custom alert despite being triggered, because there is no custom url configured")
+					}
+				}
+				if alertProvider != nil {
+					err := alertProvider.Send(service.Name, alertTriggered.Description)
+					if err != nil {
+						log.Printf("[watchdog][monitor] Ran into error sending an alert: %s", err.Error())
+					}
+				}
+			}
+		}
+
+		log.Printf("[watchdog][monitor] Waiting for interval=%s before monitoring serviceName=%s", service.Interval, service.Name)
+		time.Sleep(service.Interval)
 	}
 }