sdk/trace: batchSpanProcessor.ForceFlush calls SpanExporter.ExportSpans synchronously

CHANGELOG.md

@@ -8,6 +8,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+### Changed
+
+- `ForceFlush` of the `NewBatchSpanProcessor` in `go.opentelemetry.io/otel/sdk/trace` calls `SpanExporter.ExportSpans` synchronously. (#6416)
+
 ### Removed
 
 - Drop support for [Go 1.22]. (#6381, #6418)

sdk/trace/batch_span_processor.go

@@ -186,33 +186,23 @@ func (bsp *batchSpanProcessor) ForceFlush(ctx context.Context) error {
 		return nil
 	}
 
-	var err error
-	if bsp.e != nil {
-		flushCh := make(chan struct{})
-		if bsp.enqueueBlockOnQueueFull(ctx, forceFlushSpan{flushed: flushCh}) {
-			select {
-			case <-bsp.stopCh:
-				// The batchSpanProcessor is Shutdown.
-				return nil
-			case <-flushCh:
-				// Processed any items in queue prior to ForceFlush being called
-			case <-ctx.Done():
-				return ctx.Err()
-			}
-		}
+	if bsp.e == nil {
+		return nil
+	}
 
-		wait := make(chan error, 1)
-		go func() {
-			wait <- bsp.exportSpans(ctx)
-		}()
-		// Wait until the export is finished or the context is cancelled/timed out
+	flushCh := make(chan struct{})
+	if bsp.enqueueBlockOnQueueFull(ctx, forceFlushSpan{flushed: flushCh}) {
 		select {
-		case err = <-wait:
+		case <-bsp.stopCh:
+			// The batchSpanProcessor is Shutdown.
+			return nil
+		case <-flushCh:
+			// Processed any items in queue prior to ForceFlush being called
 		case <-ctx.Done():
-			err = ctx.Err()
+			return ctx.Err()
 		}
 	}
-	return err
+	return bsp.exportSpans(ctx)
 }
 
 // WithMaxQueueSize returns a BatchSpanProcessorOption that configures the

sdk/trace/batch_span_processor_test.go

@@ -524,24 +524,13 @@ func assertMaxSpanDiff(t *testing.T, want, got, maxDif int) {
 	}
 }
 
-type indefiniteExporter struct {
-	stop chan (struct{})
-}
-
-func newIndefiniteExporter(t *testing.T) indefiniteExporter {
-	e := indefiniteExporter{stop: make(chan struct{})}
-	t.Cleanup(func() {
-		go close(e.stop)
-	})
-	return e
-}
+type indefiniteExporter struct{}
 
 func (e indefiniteExporter) Shutdown(context.Context) error {
 	return nil
 }
 
 func (e indefiniteExporter) ExportSpans(ctx context.Context, _ []ReadOnlySpan) error {
-	<-e.stop
 	return ctx.Err()
 }
 
@@ -550,7 +539,7 @@ func TestBatchSpanProcessorForceFlushCancellation(t *testing.T) {
 	// Cancel the context
 	cancel()
 
-	bsp := NewBatchSpanProcessor(newIndefiniteExporter(t))
+	bsp := NewBatchSpanProcessor(indefiniteExporter{})
 	t.Cleanup(func() {
 		assert.NoError(t, bsp.Shutdown(context.Background()))
 	})
@@ -560,24 +549,6 @@ func TestBatchSpanProcessorForceFlushCancellation(t *testing.T) {
 	}
 }
 
-func TestBatchSpanProcessorForceFlushTimeout(t *testing.T) {
-	tp := basicTracerProvider(t)
-	exp := newIndefiniteExporter(t)
-	bsp := NewBatchSpanProcessor(exp)
-	tp.RegisterSpanProcessor(bsp)
-	tr := tp.Tracer(t.Name())
-	_, span := tr.Start(context.Background(), "foo")
-	span.End()
-
-	// Add timeout to context to test deadline
-	ctx, cancel := context.WithTimeout(context.Background(), time.Millisecond)
-	defer cancel()
-
-	if got, want := bsp.ForceFlush(ctx), context.DeadlineExceeded; !errors.Is(got, want) {
-		t.Errorf("expected %q error, got %v", want, got)
-	}
-}
-
 func TestBatchSpanProcessorForceFlushQueuedSpans(t *testing.T) {
 	ctx := context.Background()