fix race condition in reading record and updating record. (#1104)

stats/view/worker.go

@@ -236,6 +236,8 @@ func (w *worker) reportView(v *viewInternal, now time.Time) {
 }
 
 func (w *worker) reportUsage(now time.Time) {
+ w.mu.Lock()
+ defer w.mu.Unlock()
  for _, v := range w.views {
  w.reportView(v, now)
  }

stats/view/worker_commands.go

@@ -121,6 +121,8 @@ type retrieveDataResp struct {
 }
 
 func (cmd *retrieveDataReq) handleCommand(w *worker) {
+ w.mu.Lock()
+ defer w.mu.Unlock()
  vi, ok := w.views[cmd.v]
  if !ok {
  cmd.c <- &retrieveDataResp{
@@ -153,6 +155,8 @@ type recordReq struct {
 }
 
 func (cmd *recordReq) handleCommand(w *worker) {
+ w.mu.Lock()
+ defer w.mu.Unlock()
  for _, m := range cmd.ms {
  if (m == stats.Measurement{}) { // not registered
  continue

stats/view/worker_test.go

@@ -22,6 +22,8 @@ import (
  "testing"
  "time"
 
+ "go.opencensus.io/metric/metricdata"
+ "go.opencensus.io/metric/metricexport"
  "go.opencensus.io/stats"
  "go.opencensus.io/tag"
 )
@@ -397,6 +399,91 @@ func TestUnregisterReportsUsage(t *testing.T) {
  }
 }
 
+func TestWorkerRace(t *testing.T) {
+ restart()
+ ctx := context.Background()
+
+ m1 := stats.Int64("measure", "desc", "unit")
+ view1 := &View{Name: "count", Measure: m1, Aggregation: Count()}
+ m2 := stats.Int64("measure2", "desc", "unit")
+ view2 := &View{Name: "count2", Measure: m2, Aggregation: Count()}
+
+ // 1. This will export every microsecond.
+ SetReportingPeriod(time.Microsecond)
+
+ if err := Register(view1, view2); err != nil {
+ t.Fatalf("cannot register: %v", err)
+ }
+
+ e := &countExporter{}
+ RegisterExporter(e)
+
+ // Synchronize and make sure every goroutine has terminated before we exit
+ var waiter sync.WaitGroup
+ waiter.Add(3)
+ defer waiter.Wait()
+
+ doneCh := make(chan bool)
+ // 2. Record write routine at 700ns
+ go func() {
+ defer waiter.Done()
+ tick := time.NewTicker(700 * time.Nanosecond)
+ defer tick.Stop()
+
+ defer func() {
+ close(doneCh)
+ }()
+
+ for i := 0; i < 1e3; i++ {
+ stats.Record(ctx, m1.M(1))
+ stats.Record(ctx, m2.M(1))
+ stats.Record(ctx, m2.M(1))
+ <-tick.C
+ }
+ }()
+
+ // 2. Simulating RetrieveData 900ns
+ go func() {
+ defer waiter.Done()
+ tick := time.NewTicker(900 * time.Nanosecond)
+ defer tick.Stop()
+
+ for {
+ select {
+ case <-doneCh:
+ return
+ case <-tick.C:
+ RetrieveData(view1.Name)
+ }
+ }
+ }()
+
+ // 4. Export via Reader routine at 800ns
+ go func() {
+ defer waiter.Done()
+ tick := time.NewTicker(800 * time.Nanosecond)
+ defer tick.Stop()
+
+ reader := metricexport.Reader{}
+ for {
+ select {
+ case <-doneCh:
+ return
+ case <-tick.C:
+ // Perform some collection here
+ reader.ReadAndExport(&testExporter{})
+ }
+ }
+ }()
+}
+
+type testExporter struct {
+}
+
+func (te *testExporter) ExportMetrics(ctx context.Context, metrics []*metricdata.Metric) error {
+ return nil
+}
+
 type countExporter struct {
  sync.Mutex
  count int64