feat: add close method to sink

example/main.go

@@ -56,9 +56,11 @@ func main() {
 		DebugLogs:         true,
 		ReportingInterval: 35 * time.Second,
 	})
+	defer ss.Close(context.Background())
+
 	cfg := metrics.DefaultConfig("go-metrics-stackdriver")
 	cfg.EnableHostname = false
-	metrics.NewGlobal(metrics.DefaultConfig("go-metrics-stackdriver"), ss)
+	metrics.NewGlobal(cfg, ss)
 
 	// start listener
 	log.Printf("starting server")
@@ -89,7 +91,7 @@ func main() {
 		<-c
 		log.Printf("ctrl+c detected... shutting down")
 		cancel()
-		srv.Shutdown(ctx)
+		srv.Shutdown(context.Background())
 	}()
 
 	// generate data

stackdriver.go

@@ -50,9 +50,12 @@ type Logger interface {
 // Sink performs in-process aggregation of metrics to limit calls to
 // stackdriver.
 type Sink struct {
-	client    *monitoring.MetricClient
-	interval  time.Duration
-	firstTime time.Time
+	client         *monitoring.MetricClient
+	interval       time.Duration
+	firstTime      time.Time
+	closeCtx       context.Context
+	closeCtxCancel context.CancelFunc
+	closeDoneC     chan struct{}
 
 	gauges     map[string]*gauge
 	counters   map[string]*counter
@@ -199,10 +202,13 @@ func NewSink(client *monitoring.MetricClient, config *Config) *Sink {
 			Job:       config.Job,
 			TaskID:    config.TaskID,
 		},
-		debugLogs: config.DebugLogs,
-		log:       config.Logger,
+		debugLogs:  config.DebugLogs,
+		log:        config.Logger,
+		closeDoneC: make(chan struct{}),
 	}
 
+	s.closeCtx, s.closeCtxCancel = context.WithCancel(context.Background())
+
 	if s.log == nil {
 		s.log = log.New(os.Stderr, "go-metrics-stackdriver: ", log.LstdFlags)
 	}
@@ -263,7 +269,7 @@ func NewSink(client *monitoring.MetricClient, config *Config) *Sink {
 	s.reset()
 
 	// run cancelable goroutine that reports on interval
-	go s.flushMetrics(context.Background())
+	go s.reportOnInterval()
 
 	return s
 }
@@ -274,7 +280,7 @@ func isValidMetricsPrefix(s string) bool {
 	return err == nil && match
 }
 
-func (s *Sink) flushMetrics(ctx context.Context) {
+func (s *Sink) reportOnInterval() {
 	if s.interval == 0*time.Second {
 		return
 	}
@@ -284,11 +290,12 @@ func (s *Sink) flushMetrics(ctx context.Context) {
 
 	for {
 		select {
-		case <-ctx.Done():
-			s.log.Println("stopped flushing metrics")
+		case <-s.closeCtx.Done():
+			s.log.Println("stopped reporting metrics on interval")
+			close(s.closeDoneC)
 			return
 		case <-ticker.C:
-			s.report(ctx)
+			s.report(s.closeCtx)
 		}
 	}
 }
@@ -561,6 +568,20 @@ func (s *Sink) AddSampleWithLabels(key []string, val float32, labels []metrics.L
 	}
 }
 
+// Close closes the sink and flushes any remaining data.
+func (s *Sink) Close(ctx context.Context) error {
+	s.closeCtxCancel()
+	select {
+	case <-ctx.Done():
+		s.log.Println("sink close finished prematurely")
+		return ctx.Err()
+	case <-s.closeDoneC:
+	}
+	s.report(ctx)
+
+	return nil
+}
+
 var _ metrics.MetricSink = (*Sink)(nil)
 
 // Series holds the naming for a timeseries metric.

stackdriver_test.go

@@ -127,6 +127,7 @@ func TestNewSinkSetCustomPrefix(t *testing.T) {
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {
 			ss := NewSink(nil, &Config{Prefix: tc.configPrefix})
+			defer ss.Close(context.Background())
 
 			if ss.prefix != tc.expectedPrefix {
 				t.Errorf("prefix should be initalized as '" + tc.expectedPrefix + "' but got " + ss.prefix)
@@ -1044,7 +1045,7 @@ func newTestSink(interval time.Duration, client *monitoring.MetricClient) *Sink
 	s.extractor = DefaultLabelExtractor
 	s.log = log.New(os.Stderr, "go-metrics-stackdriver: ", log.LstdFlags)
 	s.reset()
-	go s.flushMetrics(context.Background())
+	go s.reportOnInterval()
 	return s
 }
 
@@ -1123,6 +1124,7 @@ func TestCustomMonitorResource(t *testing.T) {
 			Type:   "k8s_container",
 		},
 	})
+	defer sink.Close(context.Background())
 
 	monitoredResourceDiff(t, sink, labels)
 }
@@ -1132,6 +1134,7 @@ func TestCustomMonitorResourceWithDefaultLabels(t *testing.T) {
 		ProjectID: "example_project",
 		Prefix:    sPtr(""),
 	})
+	defer sink.Close(context.Background())
 
 	labels := defaultMonitoredResource(sink.taskInfo).GetLabels()
 
@@ -1160,6 +1163,7 @@ func TestCustomMonitorResourceWithInvalidLabels(t *testing.T) {
 			Type:   "k8s_container",
 		},
 	})
+	defer sink.Close(context.Background())
 
 	if diff := cmp.Diff(sink.monitoredResource.GetLabels(), invalidLabels); diff == "" {
 		t.Error("Monitored Resource labels should not be equal")