Split large jaeger span batch to admire the udp packet size limit (#1853)

* Split large jaeger span batch to admire the udp packet size

* Refactory EmitBatch and produce complaining error msg when serialization fails

* Add tests for large jaeger spans
Update CHANGELOG.md

* Update CHANGELOG.md

* Fix compatibility-test on windows.

* Add test case for exporting spans with multiple errors.

CHANGELOG.md

@@ -93,6 +93,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
   - `OTEL_EXPORTER_OTLP_TRACES_CERTIFICATE`
   - `OTEL_EXPORTER_OTLP_METRICS_CERTIFICATE`
 - Adds `otlpgrpc.WithTimeout` option for configuring timeout to the otlp/gRPC exporter. (#1821)
+- Adds `jaeger.WithMaxPacketSize` option for configuring maximum UDP packet size used when connecting to the Jaeger agent. (#1853)
 
 ### Fixed
 
@@ -104,6 +105,8 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Zipkin Exporter: Ensure mapping between OTel and Zipkin span data complies with the specification. (#1688)
 - Fixed typo for default service name in Jaeger Exporter. (#1797)
 - Fix flaky OTLP for the reconnnection of the client connection. (#1527, #1814)
+- Fix Jaeger exporter dropping of span batches that exceed the UDP packet size limit.
+  Instead, the exporter now splits the batch into smaller sendable batches. (#1828)
 
 ### Changed
 

exporters/trace/jaeger/agent.go

@@ -20,6 +20,7 @@ import (
 	"io"
 	"log"
 	"net"
+	"strings"
 	"time"
 
 	"go.opentelemetry.io/otel/exporters/trace/jaeger/internal/third_party/thrift/lib/go/thrift"
@@ -40,6 +41,7 @@ type agentClientUDP struct {
 	client         *genAgent.AgentClient
 	maxPacketSize  int                   // max size of datagram in bytes
 	thriftBuffer   *thrift.TMemoryBuffer // buffer used to calculate byte size of a span
+	thriftProtocol thrift.TProtocol
 }
 
 type udpConn interface {
@@ -75,6 +77,7 @@ func newAgentClientUDP(params agentClientUDPParams) (*agentClientUDP, error) {
 
 	thriftBuffer := thrift.NewTMemoryBufferLen(params.MaxPacketSize)
 	protocolFactory := thrift.NewTCompactProtocolFactoryConf(&thrift.TConfiguration{})
+	thriftProtocol := protocolFactory.GetProtocol(thriftBuffer)
 	client := genAgent.NewAgentClientFactory(thriftBuffer, protocolFactory)
 
 	var connUDP udpConn
@@ -107,11 +110,74 @@ func newAgentClientUDP(params agentClientUDPParams) (*agentClientUDP, error) {
 		client:         client,
 		maxPacketSize:  params.MaxPacketSize,
 		thriftBuffer:   thriftBuffer,
+		thriftProtocol: thriftProtocol,
 	}, nil
 }
 
-// EmitBatch implements EmitBatch() of Agent interface
+// EmitBatch buffers batch to fit into UDP packets and sends the data to the agent.
 func (a *agentClientUDP) EmitBatch(ctx context.Context, batch *gen.Batch) error {
+	var errs []error
+	processSize, err := a.calcSizeOfSerializedThrift(ctx, batch.Process)
+	if err != nil {
+		// drop the batch if serialization of process fails.
+		return err
+	}
+	totalSize := processSize
+	var spans []*gen.Span
+	for _, span := range batch.Spans {
+		spanSize, err := a.calcSizeOfSerializedThrift(ctx, span)
+		if err != nil {
+			errs = append(errs, fmt.Errorf("thrift serialization failed: %v", span))
+			continue
+		}
+		if spanSize+processSize >= a.maxPacketSize {
+			// drop the span that exceeds the limit.
+			errs = append(errs, fmt.Errorf("span too large to send: %v", span))
+			continue
+		}
+		if totalSize+spanSize >= a.maxPacketSize {
+			if err := a.flush(ctx, &gen.Batch{
+				Process: batch.Process,
+				Spans:   spans,
+			}); err != nil {
+				errs = append(errs, err)
+			}
+			spans = spans[:0]
+			totalSize = processSize
+		}
+		totalSize += spanSize
+		spans = append(spans, span)
+	}
+
+	if len(spans) > 0 {
+		if err := a.flush(ctx, &gen.Batch{
+			Process: batch.Process,
+			Spans:   spans,
+		}); err != nil {
+			errs = append(errs, err)
+		}
+	}
+
+	if len(errs) == 1 {
+		return errs[0]
+	} else if len(errs) > 1 {
+		joined := a.makeJoinedErrorString(errs)
+		return fmt.Errorf("multiple errors during transform: %s", joined)
+	}
+	return nil
+}
+
+// makeJoinedErrorString join all the errors to one error message.
+func (a *agentClientUDP) makeJoinedErrorString(errs []error) string {
+	var errMsgs []string
+	for _, err := range errs {
+		errMsgs = append(errMsgs, err.Error())
+	}
+	return strings.Join(errMsgs, ", ")
+}
+
+// flush will send the batch of spans to the agent.
+func (a *agentClientUDP) flush(ctx context.Context, batch *gen.Batch) error {
 	a.thriftBuffer.Reset()
 	if err := a.client.EmitBatch(ctx, batch); err != nil {
 		return err
@@ -124,6 +190,13 @@ func (a *agentClientUDP) EmitBatch(ctx context.Context, batch *gen.Batch) error
 	return err
 }
 
+// calcSizeOfSerializedThrift calculate the serialized thrift packet size.
+func (a *agentClientUDP) calcSizeOfSerializedThrift(ctx context.Context, thriftStruct thrift.TStruct) (int, error) {
+	a.thriftBuffer.Reset()
+	err := thriftStruct.Write(ctx, a.thriftProtocol)
+	return a.thriftBuffer.Len(), err
+}
+
 // Close implements Close() of io.Closer and closes the underlying UDP connection.
 func (a *agentClientUDP) Close() error {
 	return a.connUDP.Close()

exporters/trace/jaeger/agent_test.go

@@ -14,12 +14,16 @@
 package jaeger
 
 import (
+	"context"
 	"log"
 	"net"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/otel"
+	tracesdk "go.opentelemetry.io/otel/sdk/trace"
 )
 
 func TestNewAgentClientUDPWithParamsBadHostport(t *testing.T) {
@@ -99,3 +103,74 @@ func TestNewAgentClientUDPWithParamsReconnectingDisabled(t *testing.T) {
 
 	assert.NoError(t, agentClient.Close())
 }
+
+type errorHandler struct{ t *testing.T }
+
+func (eh errorHandler) Handle(err error) { assert.NoError(eh.t, err) }
+
+func TestJaegerAgentUDPLimitBatching(t *testing.T) {
+	otel.SetErrorHandler(errorHandler{t})
+
+	// 1500 spans, size 79559, does not fit within one UDP packet with the default size of 65000.
+	n := 1500
+	s := make([]*tracesdk.SpanSnapshot, n)
+	for i := 0; i < n; i++ {
+		s[i] = &tracesdk.SpanSnapshot{}
+	}
+
+	exp, err := NewRawExporter(
+		WithAgentEndpoint(WithAgentHost("localhost"), WithAgentPort("6831")),
+	)
+	require.NoError(t, err)
+
+	ctx := context.Background()
+	assert.NoError(t, exp.ExportSpans(ctx, s))
+	assert.NoError(t, exp.Shutdown(ctx))
+}
+
+// generateALargeSpan generates a span with a long name.
+func generateALargeSpan() *tracesdk.SpanSnapshot {
+	span := &tracesdk.SpanSnapshot{
+		Name: "a-longer-name-that-makes-it-exceeds-limit",
+	}
+	return span
+}
+
+func TestSpanExceedsMaxPacketLimit(t *testing.T) {
+	otel.SetErrorHandler(errorHandler{t})
+
+	// 106 is the serialized size of a span with default values.
+	maxSize := 106
+	span := generateALargeSpan()
+
+	largeSpans := []*tracesdk.SpanSnapshot{span, {}}
+	normalSpans := []*tracesdk.SpanSnapshot{{}, {}}
+
+	exp, err := NewRawExporter(
+		WithAgentEndpoint(WithAgentHost("localhost"), WithAgentPort("6831"), WithMaxPacketSize(maxSize+1)),
+	)
+	require.NoError(t, err)
+
+	ctx := context.Background()
+	assert.Error(t, exp.ExportSpans(ctx, largeSpans))
+	assert.NoError(t, exp.ExportSpans(ctx, normalSpans))
+	assert.NoError(t, exp.Shutdown(ctx))
+}
+
+func TestEmitBatchWithMultipleErrors(t *testing.T) {
+	otel.SetErrorHandler(errorHandler{t})
+
+	span := generateALargeSpan()
+	largeSpans := []*tracesdk.SpanSnapshot{span, span}
+	// make max packet size smaller than span
+	maxSize := len(span.Name)
+	exp, err := NewRawExporter(
+		WithAgentEndpoint(WithAgentHost("localhost"), WithAgentPort("6831"), WithMaxPacketSize(maxSize)),
+	)
+	require.NoError(t, err)
+
+	ctx := context.Background()
+	err = exp.ExportSpans(ctx, largeSpans)
+	assert.Error(t, err)
+	require.Contains(t, err.Error(), "multiple errors")
+}

exporters/trace/jaeger/uploader.go

@@ -114,6 +114,13 @@ func WithAttemptReconnectingInterval(interval time.Duration) AgentEndpointOption
 	}
 }
 
+// WithMaxPacketSize sets the maximum UDP packet size for transport to the Jaeger agent.
+func WithMaxPacketSize(size int) AgentEndpointOption {
+	return func(o *AgentEndpointOptions) {
+		o.MaxPacketSize = size
+	}
+}
+
 // WithCollectorEndpoint defines the full url to the Jaeger HTTP Thrift collector. This will
 // use the following environment variables for configuration if no explicit option is provided:
 //