Add flag to determine whether SpanContext is remote (#1701)

* Add remote property to SpanContext

* Set SpanContext.remote when extracting context in TraceContext propagator

* Ensure remote flag is set when inserting remote SpanContext into context

* Ensure tests are expecting remote flag in SpanContext where appropriate

* Update CHANGELOG.md

* Apply PR feedback

Co-authored-by: Tyler Yahn <[email protected]>

Co-authored-by: Tyler Yahn <[email protected]>

Author: Aneurysm9

CHANGELOG.md

@@ -14,6 +14,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - A `ForceFlush` method to the `"go.opentelemetry.io/otel/sdk/trace".TracerProvider` to flush all registered `SpanProcessor`s. (#1608)
 - Added `WithDefaultSampler` and `WithSpanLimits` to tracer provider. (#1633)
 - Jaeger exporter falls back to `resource.Default`'s `service.name` if the exported Span does not have one. (#1673)
+- `"go.opentelemetry.io/otel/trace".SpanContext` now has a `remote` property, and `IsRemote()` predicate, that is true when the `SpanContext` has been extracted from remote context data. (#1701)
 - A `Valid` method to the `"go.opentelemetry.io/otel/attribute".KeyValue` type. (#1703)
 
 ### Changed

exporters/stdout/trace_test.go

@@ -83,7 +83,7 @@ func TestExporter_ExportSpan(t *testing.T) {
 		`{` +
 		`"Key":"key",` +
 		`"Value":{"Type":"STRING","Value":"val"}` +
-		`}]},` +
+		`}],"Remote":false},` +
 		`"ParentSpanID":"0000000000000000",` +
 		`"SpanKind":1,` +
 		`"Name":"/foo",` +

oteltest/tracer_test.go

@@ -184,6 +184,8 @@ func TestTracer(t *testing.T) {
 			parentSpanContext := parentSpan.SpanContext()
 			remoteParentSpanContext := remoteParentSpan.SpanContext()
 			parentCtx = trace.ContextWithRemoteSpanContext(parentCtx, remoteParentSpanContext)
+			// remote SpanContexts will be marked as remote
+			remoteParentSpanContext = remoteParentSpanContext.WithRemote(true)
 
 			_, span := subject.Start(parentCtx, "child", trace.WithNewRoot())
 

propagation/trace_context.go

@@ -133,6 +133,7 @@ func (tc TraceContext) extract(carrier TextMapCarrier) trace.SpanContext {
 	scc.TraceFlags = opts[0] & trace.FlagsSampled
 
 	scc.TraceState = parseTraceState(carrier.Get(tracestateHeader))
+	scc.Remote = true
 
 	sc := trace.NewSpanContext(scc)
 	if !sc.IsValid() {

propagation/trace_context_test.go

@@ -40,6 +40,7 @@ func TestExtractValidTraceContextFromHTTPReq(t *testing.T) {
 			wantSc: trace.NewSpanContext(trace.SpanContextConfig{
 				TraceID: traceID,
 				SpanID:  spanID,
+				Remote:  true,
 			}),
 		},
 		{
@@ -49,6 +50,7 @@ func TestExtractValidTraceContextFromHTTPReq(t *testing.T) {
 				TraceID:    traceID,
 				SpanID:     spanID,
 				TraceFlags: trace.FlagsSampled,
+				Remote:     true,
 			}),
 		},
 		{
@@ -58,6 +60,7 @@ func TestExtractValidTraceContextFromHTTPReq(t *testing.T) {
 				TraceID:    traceID,
 				SpanID:     spanID,
 				TraceFlags: trace.FlagsSampled,
+				Remote:     true,
 			}),
 		},
 		{
@@ -67,6 +70,7 @@ func TestExtractValidTraceContextFromHTTPReq(t *testing.T) {
 				TraceID:    traceID,
 				SpanID:     spanID,
 				TraceFlags: trace.FlagsSampled,
+				Remote:     true,
 			}),
 		},
 		{
@@ -75,6 +79,7 @@ func TestExtractValidTraceContextFromHTTPReq(t *testing.T) {
 			wantSc: trace.NewSpanContext(trace.SpanContextConfig{
 				TraceID: traceID,
 				SpanID:  spanID,
+				Remote:  true,
 			}),
 		},
 		{
@@ -84,6 +89,7 @@ func TestExtractValidTraceContextFromHTTPReq(t *testing.T) {
 				TraceID:    traceID,
 				SpanID:     spanID,
 				TraceFlags: trace.FlagsSampled,
+				Remote:     true,
 			}),
 		},
 		{
@@ -93,6 +99,7 @@ func TestExtractValidTraceContextFromHTTPReq(t *testing.T) {
 				TraceID:    traceID,
 				SpanID:     spanID,
 				TraceFlags: trace.FlagsSampled,
+				Remote:     true,
 			}),
 		},
 		{
@@ -102,6 +109,7 @@ func TestExtractValidTraceContextFromHTTPReq(t *testing.T) {
 				TraceID:    traceID,
 				SpanID:     spanID,
 				TraceFlags: trace.FlagsSampled,
+				Remote:     true,
 			}),
 		},
 	}
@@ -302,6 +310,7 @@ func TestTraceStatePropagation(t *testing.T) {
 				TraceID:    traceID,
 				SpanID:     spanID,
 				TraceState: state,
+				Remote:     true,
 			}),
 		},
 		{
@@ -314,6 +323,7 @@ func TestTraceStatePropagation(t *testing.T) {
 			wantSc: trace.NewSpanContext(trace.SpanContextConfig{
 				TraceID: traceID,
 				SpanID:  spanID,
+				Remote:  true,
 			}),
 		},
 		{
@@ -326,6 +336,7 @@ func TestTraceStatePropagation(t *testing.T) {
 			wantSc: trace.NewSpanContext(trace.SpanContextConfig{
 				TraceID: traceID,
 				SpanID:  spanID,
+				Remote:  true,
 			}),
 		},
 	}

sdk/trace/trace_test.go

@@ -1385,6 +1385,7 @@ func TestReadOnlySpan(t *testing.T) {
 		TraceID:    tID,
 		SpanID:     sID,
 		TraceFlags: 0x1,
+		Remote:     true,
 	})
 	ctx := trace.ContextWithRemoteSpanContext(context.Background(), parent)
 

trace/trace.go

@@ -326,6 +326,7 @@ type SpanContextConfig struct {
 	SpanID     SpanID
 	TraceFlags byte
 	TraceState TraceState
+	Remote     bool
 }
 
 // NewSpanContext constructs a SpanContext using values from the provided
@@ -336,6 +337,7 @@ func NewSpanContext(config SpanContextConfig) SpanContext {
 		spanID:     config.SpanID,
 		traceFlags: config.TraceFlags,
 		traceState: config.TraceState,
+		remote:     config.Remote,
 	}
 }
 
@@ -345,6 +347,7 @@ type SpanContext struct {
 	spanID     SpanID
 	traceFlags byte
 	traceState TraceState
+	remote     bool
 }
 
 // IsValid returns if the SpanContext is valid. A valid span context has a
@@ -353,6 +356,22 @@ func (sc SpanContext) IsValid() bool {
 	return sc.HasTraceID() && sc.HasSpanID()
 }
 
+// IsRemote indicates whether the SpanContext represents a remotely-created Span.
+func (sc SpanContext) IsRemote() bool {
+	return sc.remote
+}
+
+// WithRemote returns a copy of sc with the Remote property set to remote.
+func (sc SpanContext) WithRemote(remote bool) SpanContext {
+	return SpanContext{
+		traceID:    sc.traceID,
+		spanID:     sc.spanID,
+		traceFlags: sc.traceFlags,
+		traceState: sc.traceState,
+		remote:     remote,
+	}
+}
+
 // TraceID returns the TraceID from the SpanContext.
 func (sc SpanContext) TraceID() TraceID {
 	return sc.traceID
@@ -370,6 +389,7 @@ func (sc SpanContext) WithTraceID(traceID TraceID) SpanContext {
 		spanID:     sc.spanID,
 		traceFlags: sc.traceFlags,
 		traceState: sc.traceState,
+		remote:     sc.remote,
 	}
 }
 
@@ -390,6 +410,7 @@ func (sc SpanContext) WithSpanID(spanID SpanID) SpanContext {
 		spanID:     spanID,
 		traceFlags: sc.traceFlags,
 		traceState: sc.traceState,
+		remote:     sc.remote,
 	}
 }
 
@@ -405,6 +426,7 @@ func (sc SpanContext) WithTraceFlags(flags byte) SpanContext {
 		spanID:     sc.spanID,
 		traceFlags: flags,
 		traceState: sc.traceState,
+		remote:     sc.remote,
 	}
 }
 
@@ -435,6 +457,7 @@ func (sc SpanContext) WithTraceState(state TraceState) SpanContext {
 		spanID:     sc.spanID,
 		traceFlags: sc.traceFlags,
 		traceState: state,
+		remote:     sc.remote,
 	}
 }
 
@@ -443,7 +466,8 @@ func (sc SpanContext) Equal(other SpanContext) bool {
 	return sc.traceID == other.traceID &&
 		sc.spanID == other.spanID &&
 		sc.traceFlags == other.traceFlags &&
-		sc.traceState.String() == other.traceState.String()
+		sc.traceState.String() == other.traceState.String() &&
+		sc.remote == other.remote
 }
 
 // MarshalJSON implements a custom marshal function to encode a SpanContext.
@@ -453,6 +477,7 @@ func (sc SpanContext) MarshalJSON() ([]byte, error) {
 		SpanID:     sc.spanID,
 		TraceFlags: sc.traceFlags,
 		TraceState: sc.traceState,
+		Remote:     sc.remote,
 	})
 }
 
@@ -487,7 +512,7 @@ func SpanContextFromContext(ctx context.Context) SpanContext {
 // ContextWithRemoteSpanContext returns a copy of parent with a remote set as
 // the remote span context.
 func ContextWithRemoteSpanContext(parent context.Context, remote SpanContext) context.Context {
-	return context.WithValue(parent, remoteContextKey, remote)
+	return context.WithValue(parent, remoteContextKey, remote.WithRemote(true))
 }
 
 // RemoteSpanContextFromContext returns the remote span context from ctx.

trace/trace_test.go

@@ -80,6 +80,8 @@ func TestContextRemoteSpanContext(t *testing.T) {
 
 	want := SpanContext{traceID: [16]byte{1}, spanID: [8]byte{42}}
 	ctx = ContextWithRemoteSpanContext(ctx, want)
+	want = want.WithRemote(true)
+
 	if got, ok := ctx.Value(remoteContextKey).(SpanContext); !ok {
 		t.Errorf("failed to set SpanContext with %#v", want)
 	} else if !assertSpanContextEqual(got, want) {
@@ -92,6 +94,8 @@ func TestContextRemoteSpanContext(t *testing.T) {
 
 	want = SpanContext{traceID: [16]byte{1}, spanID: [8]byte{43}}
 	ctx = ContextWithRemoteSpanContext(ctx, want)
+	want = want.WithRemote(true)
+
 	if got, ok := ctx.Value(remoteContextKey).(SpanContext); !ok {
 		t.Errorf("failed to set SpanContext with %#v", want)
 	} else if !assertSpanContextEqual(got, want) {
@@ -982,6 +986,7 @@ func assertSpanContextEqual(got SpanContext, want SpanContext) bool {
 	return got.spanID == want.spanID &&
 		got.traceID == want.traceID &&
 		got.traceFlags == want.traceFlags &&
+		got.remote == want.remote &&
 		assertTraceStateEqual(got.traceState, want.traceState)
 }