Infer destination service resource adapt public api (#1003)

model/model.go

@@ -371,11 +371,11 @@ type DestinationSpanContext struct {
 // DestinationServiceSpanContext holds contextual information about a
 // destination service.
 type DestinationServiceSpanContext struct {
-	// Type holds the destination service type.
+	// Type holds the destination service type. Deprecated.
 	Type string `json:"type,omitempty"`
 
-	// Name holds the destination service name.
-	Name string `json:"name,omitempty"`
+	// Name holds the destination service name. Deprecated.
+	Name string `json:"name"`
 
 	// Resource identifies the destination service
 	// resource, e.g. a URI or message queue name.

span.go

@@ -64,7 +64,7 @@ func (tx *Transaction) StartSpan(name, spanType string, parent *Span) *Span {
 // span type, subtype, and action; a single dot separates span type and
 // subtype, and the action will not be set.
 func (tx *Transaction) StartSpanOptions(name, spanType string, opts SpanOptions) *Span {
-	if tx == nil {
+	if tx == nil || opts.parent.IsExitSpan() {
 		return newDroppedSpan()
 	}
 
@@ -101,6 +101,9 @@ func (tx *Transaction) StartSpanOptions(name, spanType string, opts SpanOptions)
 	span := tx.tracer.startSpan(name, spanType, transactionID, opts)
 	span.tx = tx
 	span.parent = opts.parent
+	if opts.ExitSpan {
+		span.exit = true
+	}
 
 	// Guard access to spansCreated, spansDropped, rand, and childrenTimer.
 	tx.TransactionData.mu.Lock()
@@ -143,7 +146,10 @@ func (tx *Transaction) StartSpanOptions(name, spanType string, opts SpanOptions)
 // way will not have the "max spans" configuration applied, nor will they be
 // considered in any transaction's span count.
 func (t *Tracer) StartSpan(name, spanType string, transactionID SpanID, opts SpanOptions) *Span {
-	if opts.Parent.Trace.Validate() != nil || opts.Parent.Span.Validate() != nil || transactionID.Validate() != nil {
+	if opts.Parent.Trace.Validate() != nil ||
+		opts.Parent.Span.Validate() != nil ||
+		transactionID.Validate() != nil ||
+		opts.parent.IsExitSpan() {
 		return newDroppedSpan()
 	}
 	if !opts.Parent.Options.Recorded() {
@@ -166,6 +172,9 @@ func (t *Tracer) StartSpan(name, spanType string, transactionID SpanID, opts Spa
 	instrumentationConfig := t.instrumentationConfig()
 	span.stackFramesMinDuration = instrumentationConfig.spanFramesMinDuration
 	span.stackTraceLimit = instrumentationConfig.stackTraceLimit
+	if opts.ExitSpan {
+		span.exit = true
+	}
 
 	return span
 }
@@ -179,6 +188,10 @@ type SpanOptions struct {
 	// will be generated and used instead.
 	SpanID SpanID
 
+	// Indicates whether a span is an exit span or not. All child spans
+	// will be noop spans.
+	ExitSpan bool
+
 	// parent, if non-nil, holds the parent span.
 	//
 	// This is only used if Parent is zero, and is only available to internal
@@ -239,6 +252,7 @@ type Span struct {
 	traceContext  TraceContext
 	transactionID SpanID
 	parentID      SpanID
+	exit          bool
 
 	mu sync.RWMutex
 
@@ -295,6 +309,11 @@ func (s *Span) End() {
 	if s.ended() {
 		return
 	}
+	if s.exit && !s.Context.setDestinationServiceCalled {
+		// The span was created as an exit span, but the user did not
+		// manually set the destination.service.resource
+		s.setExitSpanDestinationService()
+	}
 	if s.Duration < 0 {
 		s.Duration = time.Since(s.timestamp)
 	}
@@ -384,6 +403,24 @@ func (s *Span) ended() bool {
 	return s.SpanData == nil
 }
 
+func (s *Span) setExitSpanDestinationService() {
+	resource := s.Subtype
+	if resource == "" {
+		resource = s.Type
+	}
+	s.Context.SetDestinationService(DestinationServiceSpanContext{
+		Resource: resource,
+	})
+}
+
+// IsExitSpan returns true if the span is an exit span.
+func (s *Span) IsExitSpan() bool {
+	if s == nil {
+		return false
+	}
+	return s.exit
+}
+
 // SpanData holds the details for a span, and is embedded inside Span.
 // When a span is ended or discarded, its SpanData field will be set
 // to nil.

span_test.go

@@ -163,6 +163,46 @@ func TestSpanType(t *testing.T) {
 	check(spans[3], "type", "subtype", "action.figure")
 }
 
+func TestStartExitSpan(t *testing.T) {
+	_, spans, _ := apmtest.WithTransaction(func(ctx context.Context) {
+		span, _ := apm.StartSpanOptions(ctx, "name", "type", apm.SpanOptions{ExitSpan: true})
+		assert.True(t, span.IsExitSpan())
+		span.End()
+	})
+	require.Len(t, spans, 1)
+	// When the context's DestinationService is not explicitly set, ending
+	// the exit span will assign the value.
+	assert.Equal(t, spans[0].Context.Destination.Service.Resource, "type")
+
+	tracer := apmtest.NewRecordingTracer()
+	defer tracer.Close()
+
+	tx := tracer.StartTransaction("name", "type")
+	span := tx.StartSpanOptions("name", "type", apm.SpanOptions{ExitSpan: true})
+	assert.True(t, span.IsExitSpan())
+	// when the parent span is an exit span, any children should be noops.
+	span2 := tx.StartSpan("name", "type", span)
+	assert.True(t, span2.Dropped())
+	span.End()
+	span2.End()
+	// Spans should still be marked as an exit span after they've been
+	// ended.
+	assert.True(t, span.IsExitSpan())
+}
+
+func TestExitSpanDoesNotOverwriteDestinationServiceResource(t *testing.T) {
+	_, spans, _ := apmtest.WithTransaction(func(ctx context.Context) {
+		span, _ := apm.StartSpanOptions(ctx, "name", "type", apm.SpanOptions{ExitSpan: true})
+		assert.True(t, span.IsExitSpan())
+		span.Context.SetDestinationService(apm.DestinationServiceSpanContext{
+			Resource: "my-custom-resource",
+		})
+		span.End()
+	})
+	require.Len(t, spans, 1)
+	assert.Equal(t, spans[0].Context.Destination.Service.Resource, "my-custom-resource")
+}
+
 func TestTracerStartSpanIDSpecified(t *testing.T) {
 	spanID := apm.SpanID{0, 1, 2, 3, 4, 5, 6, 7}
 	_, spans, _ := apmtest.WithTransaction(func(ctx context.Context) {

spancontext.go

@@ -37,6 +37,10 @@ type SpanContext struct {
 	databaseRowsAffected int64
 	database             model.DatabaseSpanContext
 	http                 model.HTTPSpanContext
+
+	// If SetDestinationService has been called, we do not auto-set its
+	// resource value on span end.
+	setDestinationServiceCalled bool
 }
 
 // DatabaseSpanContext holds database span context.
@@ -58,7 +62,7 @@ type DatabaseSpanContext struct {
 // DestinationServiceSpanContext holds destination service span span.
 type DestinationServiceSpanContext struct {
 	// Name holds a name for the destination service, which may be used
-	// for grouping and labeling in service maps.
+	// for grouping and labeling in service maps. Deprecated.
 	Name string
 
 	// Resource holds an identifier for a destination service resource,
@@ -222,7 +226,8 @@ func (c *SpanContext) SetMessage(message MessageSpanContext) {
 // Both service.Name and service.Resource are required. If either is empty,
 // then SetDestinationService is a no-op.
 func (c *SpanContext) SetDestinationService(service DestinationServiceSpanContext) {
-	if service.Name == "" || service.Resource == "" {
+	c.setDestinationServiceCalled = true
+	if service.Resource == "" {
 		return
 	}
 	c.destinationService.Name = truncateString(service.Name)

spancontext_test.go

@@ -132,29 +132,23 @@ func TestSetDestinationService(t *testing.T) {
 	}
 
 	testcases := []testcase{{
-		name:        "",
 		resource:    "",
 		expectEmpty: true,
 	}, {
-		name:        "",
 		resource:    "nonempty",
-		expectEmpty: true,
+		expectEmpty: false,
 	}, {
-		name:        "nonempty",
 		resource:    "",
 		expectEmpty: true,
 	}, {
-		name:     "nonempty",
 		resource: "nonempty",
 	}}
-
 	for _, tc := range testcases {
 		t.Run(fmt.Sprintf("%s_%s", tc.name, tc.resource), func(t *testing.T) {
 			_, spans, _ := apmtest.WithTransaction(func(ctx context.Context) {
 				span, _ := apm.StartSpan(ctx, "name", "span_type")
 				span.Context.SetDestinationAddress("testing.invalid", 123)
 				span.Context.SetDestinationService(apm.DestinationServiceSpanContext{
-					Name:     tc.name,
 					Resource: tc.resource,
 				})
 				span.End()
@@ -164,7 +158,6 @@ func TestSetDestinationService(t *testing.T) {
 				assert.Nil(t, spans[0].Context.Destination.Service)
 			} else {
 				assert.Equal(t, &model.DestinationServiceSpanContext{
-					Name:     tc.name,
 					Resource: tc.resource,
 					Type:     "span_type",
 				}, spans[0].Context.Destination.Service)