Remove locking from Jaeger exporter shutdown/export (#1807)

exporters/trace/jaeger/jaeger.go

@@ -19,7 +19,6 @@ import (
 	"encoding/binary"
 	"encoding/json"
 	"fmt"
-	"sync"
 
 	"google.golang.org/api/support/bundler"
 
@@ -115,8 +114,10 @@ func NewRawExporter(endpointOption EndpointOption, opts ...Option) (*Exporter, e
 		return nil, fmt.Errorf("failed to get service name from default resource")
 	}
 
+	stopCh := make(chan struct{})
 	e := &Exporter{
 		uploader:           uploader,
+		stopCh:             stopCh,
 		defaultServiceName: defaultServiceName,
 	}
 	bundler := bundler.NewBundler((*sdktrace.SpanSnapshot)(nil), func(bundle interface{}) {
@@ -180,8 +181,7 @@ type Exporter struct {
 	bundler  *bundler.Bundler
 	uploader batchUploader
 
-	stoppedMu sync.RWMutex
-	stopped   bool
+	stopCh chan struct{}
 
 	defaultServiceName string
 }
@@ -190,13 +190,27 @@ var _ sdktrace.SpanExporter = (*Exporter)(nil)
 
 // ExportSpans exports SpanSnapshots to Jaeger.
 func (e *Exporter) ExportSpans(ctx context.Context, ss []*sdktrace.SpanSnapshot) error {
-	e.stoppedMu.RLock()
-	stopped := e.stopped
-	e.stoppedMu.RUnlock()
-	if stopped {
+	// Return fast if context is already canceled or Exporter shutdown.
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-e.stopCh:
 		return nil
+	default:
 	}
 
+	// Cancel export if Exporter is shutdown.
+	var cancel context.CancelFunc
+	ctx, cancel = context.WithCancel(ctx)
+	defer cancel()
+	go func(ctx context.Context, cancel context.CancelFunc) {
+		select {
+		case <-ctx.Done():
+		case <-e.stopCh:
+			cancel()
+		}
+	}(ctx, cancel)
+
 	for _, span := range ss {
 		// TODO(jbd): Handle oversized bundlers.
 		err := e.bundler.AddWait(ctx, span, 1)
@@ -220,9 +234,8 @@ var flush = func(e *Exporter) {
 
 // Shutdown stops the exporter flushing any pending exports.
 func (e *Exporter) Shutdown(ctx context.Context) error {
-	e.stoppedMu.Lock()
-	e.stopped = true
-	e.stoppedMu.Unlock()
+	// Stop any active and subsequent exports.
+	close(e.stopCh)
 
 	done := make(chan struct{}, 1)
 	// Shadow so if the goroutine is leaked in testing it doesn't cause a race
@@ -408,6 +421,12 @@ func getBoolTag(k string, b bool) *gen.Tag {
 //
 // This is useful if your program is ending and you do not want to lose recent spans.
 func (e *Exporter) Flush() {
+	// Return fast if Exporter shutdown.
+	select {
+	case <-e.stopCh:
+		return
+	default:
+	}
 	flush(e)
 }