Add Indexer.Size() and index_size metric

internal/indexer.go

@@ -10,6 +10,7 @@ import (
 
 type Indexer interface {
 	Index(entry *Entry) error
+	Size() int64
 	Search(q string, p int) (*bleve.SearchResult, error)
 }
 
@@ -40,6 +41,15 @@ func NewIndexer(conf *Config) (Indexer, error) {
 	return &indexer{conf: conf, idx: idx}, nil
 }
 
+func (i *indexer) Size() int64 {
+	count, err := i.idx.DocCount()
+	if err != nil {
+		log.WithError(err).Warn("error getting index size")
+		return 0
+	}
+	return int64(count)
+}
+
 func (i *indexer) Index(entry *Entry) error {
 	return i.idx.Index(entry.Hash(), entry)
 }

internal/server.go

@@ -217,6 +217,15 @@ func (s *Server) setupMetrics() {
 		"Duration of crawler tasks",
 	)
 
+	// Index stats
+	metrics.NewGaugeFunc(
+		"index", "size",
+		"Size of index (number of indexed entries)",
+		func() float64 {
+			return float64(s.indexer.Size())
+		},
+	)
+
 	// server info
 	metrics.NewGaugeVec(
 		"server", "info",