fixes: add quit chan, use enum, set map type

collectors/channels_collector.go

@@ -13,6 +13,8 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 )
 
+const closedChannelsKey = "closedChannels"
+
 // ChannelsCollector is a collector that keeps track of channel information.
 type ChannelsCollector struct {
 	channelBalanceDesc           *prometheus.Desc
@@ -54,9 +56,12 @@ type ChannelsCollector struct {
 	// This channel should be buffered so that it does not block sends.
 	errChan chan<- error
 
+	// quit is a channel that we use to signal for graceful shutdown
+	quit chan struct{}
+
 	// cache is a map storing results from a ticker to reduce grpc server
 	// load on lnd
-	cache      map[string]interface{}
+	cache      map[string][]lndclient.ClosedChannel
 	cacheMutex sync.RWMutex
 }
 
@@ -183,7 +188,9 @@ func NewChannelsCollector(lnd lndclient.LightningClient, errChan chan<- error,
 
 		lnd:         lnd,
 		primaryNode: cfg.PrimaryNode,
+		cache:       make(map[string][]lndclient.ClosedChannel),
 		errChan:     errChan,
+		quit:        make(chan struct{}),
 	}
 
 	// Perform an initial refresh for the cache
@@ -193,8 +200,13 @@ func NewChannelsCollector(lnd lndclient.LightningClient, errChan chan<- error,
 	go func() {
 		ticker := time.NewTicker(10 * time.Minute)
 		defer ticker.Stop()
-		for range ticker.C {
-			collector.refreshClosedChannelsCache()
+		for {
+			select {
+			case <-ticker.C:
+				collector.refreshClosedChannelsCache()
+			case <-collector.quit:
+				return
+			}
 		}
 	}()
 
@@ -208,7 +220,7 @@ func (c *ChannelsCollector) refreshClosedChannelsCache() {
 		return
 	}
 	c.cacheMutex.Lock()
-	c.cache["closedChannels"] = data
+	c.cache[closedChannelsKey] = data
 	c.cacheMutex.Unlock()
 }
 
@@ -485,11 +497,11 @@ func (c *ChannelsCollector) Collect(ch chan<- prometheus.Metric) {
 
 	// Get the list of closed channels.
 	c.cacheMutex.RLock()
-	closedChannelsResp, ok := c.cache["closedChannels"].([]*lndclient.ClosedChannel)
+	closedChannelsResp, ok := c.cache[closedChannelsKey]
 	if !ok {
 		// Cache is not initialized
 		Logger.Warn("ClosedChannels not in cache")
-		closedChannelsResp = []*lndclient.ClosedChannel{}
+		closedChannelsResp = []lndclient.ClosedChannel{}
 	}
 	c.cacheMutex.RUnlock()
 	closeCounts := make(map[string]int)

collectors/prometheus.go

@@ -5,7 +5,9 @@ import (
 	"log"
 	"net/http"
 	"os"
+	"os/signal"
 	"path/filepath"
+	"syscall"
 
 	"github.com/btcsuite/btcd/btcutil"
 	"github.com/lightninglabs/lndclient"
@@ -94,11 +96,21 @@ func NewPrometheusExporter(cfg *PrometheusConfig, lnd *lndclient.LndServices,
 
 	htlcMonitor := newHtlcMonitor(lnd.Router, errChan)
 
+	// Setup signalling so SIGTERM || SIGINT will stop the cache goroutine
+	// from ChannelsCollector
+	sigs := make(chan os.Signal, 1)
+	signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)
+	chanCollector := NewChannelsCollector(
+		lnd.Client, errChan, monitoringCfg,
+	)
+	go func() {
+		<-sigs
+		close(chanCollector.quit)
+	}()
+
 	collectors := []prometheus.Collector{
 		NewChainCollector(lnd.Client, errChan),
-		NewChannelsCollector(
-			lnd.Client, errChan, monitoringCfg,
-		),
+		chanCollector,
 		NewWalletCollector(lnd, errChan),
 		NewPeerCollector(lnd.Client, errChan),
 		NewInfoCollector(lnd.Client, errChan),