fix(runner): stop config updater on shutdown

pkg/runner/runner.go

@@ -601,13 +601,23 @@ func configUpdater(viperNotifyCh chan fsnotify.Event, edm *dnstapMinimiser) {
 	})
 	t.Stop()
 
-	for e = range viperNotifyCh {
-		// If an event has been recevied this means we now want to
-		// enable the timer so the function will be called "soon", but
-		// if more events occur we will reset it again. This allows us
-		// to wait until events on the file settles down before
-		// actually calling the update function.
-		t.Reset(100 * time.Millisecond)
+	for {
+		select {
+		case event, ok := <-viperNotifyCh:
+			if !ok {
+				return
+			}
+			e = event
+			// If an event has been recevied this means we now want to
+			// enable the timer so the function will be called "soon", but
+			// if more events occur we will reset it again. This allows us
+			// to wait until events on the file settles down before
+			// actually calling the update function.
+			t.Reset(100 * time.Millisecond)
+		case <-edm.ctx.Done():
+			t.Stop()
+			return
+		}
 	}
 }
 
@@ -1158,12 +1168,15 @@ func Run(logger *slog.Logger, loggerLevel *slog.LevelVar) {
 		os.Exit(1)
 	}
 
-	viperNotifyCh := make(chan fsnotify.Event)
+	viperNotifyCh := make(chan fsnotify.Event, 1)
 
 	go configUpdater(viperNotifyCh, edm)
 
 	viper.OnConfigChange(func(e fsnotify.Event) {
-		viperNotifyCh <- e
+		select {
+		case viperNotifyCh <- e:
+		default:
+		}
 	})
 
 	pdbDir := filepath.Join(startConf.DataDir, "pebble")
@@ -1415,6 +1428,8 @@ func Run(logger *slog.Logger, loggerLevel *slog.LevelVar) {
 	edm.log.Info("Run: waiting for other workers to exit")
 	wg.Wait()
 
+	close(viperNotifyCh)
+
 	// Wait for graceful disconnection from MQTT bus
 	if !startConf.DisableMQTT {
 		edm.log.Info("Run: waiting on MQTT disconnection")

pkg/runner/runner_test.go

@@ -10,10 +10,12 @@ import (
 	"os"
 	"slices"
 	"strings"
+	"sync"
 	"testing"
 	"time"
 
 	dnstap "github.com/dnstap/golang-dnstap"
+	"github.com/fsnotify/fsnotify"
 	"github.com/miekg/dns"
 	"github.com/parquet-go/parquet-go"
 	"github.com/parquet-go/parquet-go/format"
@@ -2145,3 +2147,35 @@ func TestWriteHistogramParquetExplicitThreshold(t *testing.T) {
 		}
 	}
 }
+func TestConfigUpdaterExitsOnContextCancel(t *testing.T) {
+	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
+	edm, err := newDnstapMinimiser(logger, defaultTC)
+	if err != nil {
+		t.Fatalf("newDnstapMinimiser: %s", err)
+	}
+	t.Cleanup(edm.stop)
+
+	viperNotifyCh := make(chan fsnotify.Event, 1)
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		configUpdater(viperNotifyCh, edm)
+	}()
+
+	time.Sleep(50 * time.Millisecond)
+
+	edm.stop()
+
+	done := make(chan struct{})
+	go func() {
+		wg.Wait()
+		close(done)
+	}()
+	select {
+	case <-done:
+	case <-time.After(2 * time.Second):
+		t.Fatal("configUpdater did not exit after context cancel")
+	}
+}