Add ForceFlush method to TracerProvider

CHANGELOG.md

@@ -14,6 +14,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - AttributePerEventCountLimit and AttributePerLinkCountLimit for SpanLimits. (#1535)
 - Added `Keys()` method to `propagation.TextMapCarrier` and `propagation.HeaderCarrier` to adapt `http.Header` to this interface. (#1544)
 - Added `code` attributes to `go.opentelemetry.io/otel/semconv` package. (#1558)
+- A `ForceFlush` method to the `"go.opentelemetry.io/otel/sdk/trace".TracerProvider` to flush all registered `SpanProcessor`s. (#1607)
 
 ### Changed
 
@@ -39,6 +40,8 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
       "otel/sdk/trace".ReadOnlySpan
       "otel/sdk/trace".ReadWriteSpan
 ```
+- Update the `ForceFlush` method signature to the `"go.opentelemetry.io/otel/sdk/trace".SpanProcessor` to accept a context.Context and return an error. (#1607)
+- Update the `Shutdown` method to the `"go.opentelemetry.io/otel/sdk/trace".TracerProvider` return an error on shutdown failure. (#1607)
 
 ### Removed
 

sdk/trace/batch_span_processor.go

@@ -150,8 +150,8 @@ func (bsp *BatchSpanProcessor) Shutdown(ctx context.Context) error {
 }
 
 // ForceFlush exports all ended spans that have not yet been exported.
-func (bsp *BatchSpanProcessor) ForceFlush() {
-	bsp.exportSpans()
+func (bsp *BatchSpanProcessor) ForceFlush(ctx context.Context) error {
+	return bsp.exportSpans(ctx)
 }
 
 func WithMaxQueueSize(size int) BatchSpanProcessorOption {
@@ -179,18 +179,19 @@ func WithBlocking() BatchSpanProcessorOption {
 }
 
 // exportSpans is a subroutine of processing and draining the queue.
-func (bsp *BatchSpanProcessor) exportSpans() {
+func (bsp *BatchSpanProcessor) exportSpans(ctx context.Context) error {
 	bsp.timer.Reset(bsp.o.BatchTimeout)
 
 	bsp.batchMutex.Lock()
 	defer bsp.batchMutex.Unlock()
 
 	if len(bsp.batch) > 0 {
-		if err := bsp.e.ExportSpans(context.Background(), bsp.batch); err != nil {
-			otel.Handle(err)
+		if err := bsp.e.ExportSpans(ctx, bsp.batch); err != nil {
+			return err
 		}
 		bsp.batch = bsp.batch[:0]
 	}
+	return nil
 }
 
 // processQueue removes spans from the `queue` channel until processor
@@ -199,12 +200,15 @@ func (bsp *BatchSpanProcessor) exportSpans() {
 func (bsp *BatchSpanProcessor) processQueue() {
 	defer bsp.timer.Stop()
 
+	ctx := context.Background()
 	for {
 		select {
 		case <-bsp.stopCh:
 			return
 		case <-bsp.timer.C:
-			bsp.exportSpans()
+			if err := bsp.exportSpans(ctx); err != nil {
+				otel.Handle(err)
+			}
 		case sd := <-bsp.queue:
 			bsp.batchMutex.Lock()
 			bsp.batch = append(bsp.batch, sd)
@@ -214,7 +218,9 @@ func (bsp *BatchSpanProcessor) processQueue() {
 				if !bsp.timer.Stop() {
 					<-bsp.timer.C
 				}
-				bsp.exportSpans()
+				if err := bsp.exportSpans(ctx); err != nil {
+					otel.Handle(err)
+				}
 			}
 		}
 	}
@@ -223,11 +229,14 @@ func (bsp *BatchSpanProcessor) processQueue() {
 // drainQueue awaits the any caller that had added to bsp.stopWait
 // to finish the enqueue, then exports the final batch.
 func (bsp *BatchSpanProcessor) drainQueue() {
+	ctx := context.Background()
 	for {
 		select {
 		case sd := <-bsp.queue:
 			if sd == nil {
-				bsp.exportSpans()
+				if err := bsp.exportSpans(ctx); err != nil {
+					otel.Handle(err)
+				}
 				return
 			}
 
@@ -237,7 +246,9 @@ func (bsp *BatchSpanProcessor) drainQueue() {
 			bsp.batchMutex.Unlock()
 
 			if shouldExport {
-				bsp.exportSpans()
+				if err := bsp.exportSpans(ctx); err != nil {
+					otel.Handle(err)
+				}
 			}
 		default:
 			close(bsp.queue)

sdk/trace/batch_span_processor_test.go

@@ -78,10 +78,11 @@ func TestNewBatchSpanProcessorWithNilExporter(t *testing.T) {
 	// These should not panic.
 	bsp.OnStart(context.Background(), span.(sdktrace.ReadWriteSpan))
 	bsp.OnEnd(span.(sdktrace.ReadOnlySpan))
-	bsp.ForceFlush()
-	err := bsp.Shutdown(context.Background())
-	if err != nil {
-		t.Error("Error shutting the BatchSpanProcessor down\n")
+	if err := bsp.ForceFlush(context.Background()); err != nil {
+		t.Errorf("failed to ForceFlush the BatchSpanProcessor: %v", err)
+	}
+	if err := bsp.Shutdown(context.Background()); err != nil {
+		t.Errorf("failed to Shutdown the BatchSpanProcessor: %v", err)
 	}
 }
 

sdk/trace/provider.go

@@ -16,6 +16,7 @@ package trace // import "go.opentelemetry.io/otel/sdk/trace"
 
 import (
 	"context"
+	"fmt"
 	"sync"
 	"sync/atomic"
 
@@ -196,19 +197,55 @@ func (p *TracerProvider) ApplyConfig(cfg Config) {
 	p.config.Store(&c)
 }
 
-// Shutdown shuts down the span processors in the order they were registered
+// ForceFlush immediately export all spans that have not yet been exported for
+// all the registered span processors.
+func (p *TracerProvider) ForceFlush(ctx context.Context) error {
+	spss, ok := p.spanProcessors.Load().(spanProcessorStates)
+	if !ok {
+		return fmt.Errorf("failed to load span processors")
+	}
+	if len(spss) == 0 {
+		return nil
+	}
+
+	for _, sps := range spss {
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		default:
+		}
+
+		if err := sps.sp.ForceFlush(ctx); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Shutdown shuts down the span processors in the order they were registered.
 func (p *TracerProvider) Shutdown(ctx context.Context) error {
 	spss, ok := p.spanProcessors.Load().(spanProcessorStates)
-	if !ok || len(spss) == 0 {
+	if !ok {
+		return fmt.Errorf("failed to load span processors")
+	}
+	if len(spss) == 0 {
 		return nil
 	}
 
 	for _, sps := range spss {
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		default:
+		}
+
+		var err error
 		sps.state.Do(func() {
-			if err := sps.sp.Shutdown(ctx); err != nil {
-				otel.Handle(err)
-			}
+			err = sps.sp.Shutdown(ctx)
 		})
+		if err != nil {
+			return err
+		}
 	}
 	return nil
 }

sdk/trace/provider_test.go

@@ -32,9 +32,11 @@ func (t *basicSpanProcesor) Shutdown(context.Context) error {
 	return t.injectShutdownError
 }
 
-func (t *basicSpanProcesor) OnStart(parent context.Context, s ReadWriteSpan) {}
-func (t *basicSpanProcesor) OnEnd(s ReadOnlySpan)                            {}
-func (t *basicSpanProcesor) ForceFlush()                                     {}
+func (t *basicSpanProcesor) OnStart(context.Context, ReadWriteSpan) {}
+func (t *basicSpanProcesor) OnEnd(ReadOnlySpan)                     {}
+func (t *basicSpanProcesor) ForceFlush(context.Context) error {
+	return nil
+}
 
 func TestShutdownTraceProvider(t *testing.T) {
 	stp := NewTracerProvider()
@@ -51,7 +53,6 @@ func TestShutdownTraceProvider(t *testing.T) {
 }
 
 func TestFailedProcessorShutdown(t *testing.T) {
-	handler.Reset()
 	stp := NewTracerProvider()
 	spErr := errors.New("basic span processor shutdown failure")
 	sp := &basicSpanProcesor{
@@ -60,9 +61,9 @@ func TestFailedProcessorShutdown(t *testing.T) {
 	}
 	stp.RegisterSpanProcessor(sp)
 
-	_ = stp.Shutdown(context.Background())
-
-	assert.Contains(t, handler.errs, spErr)
+	err := stp.Shutdown(context.Background())
+	assert.Error(t, err)
+	assert.Equal(t, err, spErr)
 }
 
 func TestFailedProcessorShutdownInUnregister(t *testing.T) {
@@ -78,7 +79,6 @@ func TestFailedProcessorShutdownInUnregister(t *testing.T) {
 
 	assert.Contains(t, handler.errs, spErr)
 
-	handler.errs = nil
-	_ = stp.Shutdown(context.Background())
-	assert.Empty(t, handler.errs)
+	err := stp.Shutdown(context.Background())
+	assert.NoError(t, err)
 }

sdk/trace/simple_span_processor.go

@@ -58,5 +58,6 @@ func (ssp *SimpleSpanProcessor) Shutdown(_ context.Context) error {
 }
 
 // ForceFlush does nothing as there is no data to flush.
-func (ssp *SimpleSpanProcessor) ForceFlush() {
+func (ssp *SimpleSpanProcessor) ForceFlush(context.Context) error {
+	return nil
 }

sdk/trace/span_processor.go

@@ -39,7 +39,7 @@ type SpanProcessor interface {
 	// been exported.  It should only be called when absolutely necessary, such as when
 	// using a FaaS provider that may suspend the process after an invocation, but before
 	// the Processor can export the completed spans.
-	ForceFlush()
+	ForceFlush(ctx context.Context) error
 }
 
 type spanProcessorState struct {

sdk/trace/span_processor_example_test.go

@@ -36,8 +36,8 @@ type DurationFilter struct {
 func (f DurationFilter) OnStart(parent context.Context, s ReadWriteSpan) {
 	f.Next.OnStart(parent, s)
 }
-func (f DurationFilter) Shutdown(ctx context.Context) error { return f.Next.Shutdown(ctx) }
-func (f DurationFilter) ForceFlush()                        { f.Next.ForceFlush() }
+func (f DurationFilter) Shutdown(ctx context.Context) error   { return f.Next.Shutdown(ctx) }
+func (f DurationFilter) ForceFlush(ctx context.Context) error { return f.Next.ForceFlush(ctx) }
 func (f DurationFilter) OnEnd(s ReadOnlySpan) {
 	if f.Min > 0 && s.EndTime().Sub(s.StartTime()) < f.Min {
 		// Drop short lived spans.
@@ -65,7 +65,9 @@ func (f InstrumentationBlacklist) OnStart(parent context.Context, s ReadWriteSpa
 	f.Next.OnStart(parent, s)
 }
 func (f InstrumentationBlacklist) Shutdown(ctx context.Context) error { return f.Next.Shutdown(ctx) }
-func (f InstrumentationBlacklist) ForceFlush()                        { f.Next.ForceFlush() }
+func (f InstrumentationBlacklist) ForceFlush(ctx context.Context) error {
+	return f.Next.ForceFlush(ctx)
+}
 func (f InstrumentationBlacklist) OnEnd(s ReadOnlySpan) {
 	if f.Blacklist != nil && f.Blacklist[s.InstrumentationLibrary().Name] {
 		// Drop spans from this instrumentation

sdk/trace/span_processor_test.go

@@ -63,7 +63,8 @@ func (t *testSpanProcessor) Shutdown(_ context.Context) error {
 	return nil
 }
 
-func (t *testSpanProcessor) ForceFlush() {
+func (t *testSpanProcessor) ForceFlush(context.Context) error {
+	return nil
 }
 
 func TestRegisterSpanProcessor(t *testing.T) {