Handle tracestate in TraceContext propagator

CHANGELOG.md

@@ -31,6 +31,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Metric aggregator Count() and histogram Bucket.Counts are consistently `uint64`. (1430)
 - `SamplingResult` now passed a `Tracestate` from the parent `SpanContext` (#1432)
 - Moved gRPC driver for OTLP exporter to `exporters/otlp/otlpgrpc`. (#1420)
+- The `TraceContext` propagator now correctly propagates `TraceState` through the `SpanContext`. (#1447)
 
 ### Removed
 

propagation/trace_context.go

@@ -19,7 +19,9 @@ import (
 	"encoding/hex"
 	"fmt"
 	"regexp"
+	"strings"
 
+	"go.opentelemetry.io/otel/label"
 	"go.opentelemetry.io/otel/trace"
 )
 
@@ -30,12 +32,6 @@ const (
 	tracestateHeader  = "tracestate"
 )
 
-type traceContextPropagatorKeyType uint
-
-const (
-	tracestateKey traceContextPropagatorKeyType = 0
-)
-
 // TraceContext is a propagator that supports the W3C Trace Context format
 // (https://www.w3.org/TR/trace-context/)
 //
@@ -51,15 +47,13 @@ var traceCtxRegExp = regexp.MustCompile("^(?P<version>[0-9a-f]{2})-(?P<traceID>[
 
 // Inject set tracecontext from the Context into the carrier.
 func (tc TraceContext) Inject(ctx context.Context, carrier TextMapCarrier) {
-	tracestate := ctx.Value(tracestateKey)
-	if state, ok := tracestate.(string); tracestate != nil && ok {
-		carrier.Set(tracestateHeader, state)
-	}
-
 	sc := trace.SpanContextFromContext(ctx)
 	if !sc.IsValid() {
 		return
 	}
+
+	carrier.Set(tracestateHeader, sc.TraceState.String())
+
 	h := fmt.Sprintf("%.2x-%s-%s-%.2x",
 		supportedVersion,
 		sc.TraceID,
@@ -70,11 +64,6 @@ func (tc TraceContext) Inject(ctx context.Context, carrier TextMapCarrier) {
 
 // Extract reads tracecontext from the carrier into a returned Context.
 func (tc TraceContext) Extract(ctx context.Context, carrier TextMapCarrier) context.Context {
-	state := carrier.Get(tracestateHeader)
-	if state != "" {
-		ctx = context.WithValue(ctx, tracestateKey, state)
-	}
-
 	sc := tc.extract(carrier)
 	if !sc.IsValid() {
 		return ctx
@@ -143,6 +132,12 @@ func (tc TraceContext) extract(carrier TextMapCarrier) trace.SpanContext {
 	// Clear all flags other than the trace-context supported sampling bit.
 	sc.TraceFlags = opts[0] & trace.FlagsSampled
 
+	ts, err := parseTraceState(carrier.Get(tracestateHeader))
+	if err != nil {
+		return trace.SpanContext{}
+	}
+	sc.TraceState = ts
+
 	if !sc.IsValid() {
 		return trace.SpanContext{}
 	}
@@ -154,3 +149,16 @@ func (tc TraceContext) extract(carrier TextMapCarrier) trace.SpanContext {
 func (tc TraceContext) Fields() []string {
 	return []string{traceparentHeader, tracestateHeader}
 }
+
+func parseTraceState(in string) (trace.TraceState, error) {
+	if in == "" {
+		return trace.TraceState{}, nil
+	}
+
+	kvs := []label.KeyValue{}
+	for _, entry := range strings.Split(in, ",") {
+		parts := strings.SplitN(entry, "=", 2)
+		kvs = append(kvs, label.String(parts[0], parts[1]))
+	}
+	return trace.TraceStateFromKeyValues(kvs...)
+}

propagation/trace_context_test.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/google/go-cmp/cmp"
 
+	"go.opentelemetry.io/otel/label"
 	"go.opentelemetry.io/otel/oteltest"
 	"go.opentelemetry.io/otel/propagation"
 	"go.opentelemetry.io/otel/trace"
@@ -277,17 +278,67 @@ func TestTraceContextPropagator_GetAllKeys(t *testing.T) {
 
 func TestTraceStatePropagation(t *testing.T) {
 	prop := propagation.TraceContext{}
-	want := "opaquevalue"
-	headerName := "tracestate"
+	stateHeader := "tracestate"
+	parentHeader := "traceparent"
+	state, _ := trace.TraceStateFromKeyValues(label.String("key1", "value1"), label.String("key2", "value2"))
 
-	inReq, _ := http.NewRequest(http.MethodGet, "http://example.com", nil)
-	inReq.Header.Add(headerName, want)
-	ctx := prop.Extract(context.Background(), inReq.Header)
+	tests := []struct {
+		name    string
+		headers map[string]string
+		valid   bool
+		wantSc  trace.SpanContext
+	}{
+		{
+			name: "valid parent and state",
+			headers: map[string]string{
+				parentHeader: "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-00",
+				stateHeader:  "key1=value1,key2=value2",
+			},
+			valid: true,
+			wantSc: trace.SpanContext{
+				TraceID:    traceID,
+				SpanID:     spanID,
+				TraceState: state,
+			},
+		},
+		{
+			name: "valid parent, invalid state",
+			headers: map[string]string{
+				parentHeader: "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-00",
+				stateHeader:  "key1=value1,invalid$@#=invalid",
+			},
+			valid:  false,
+			wantSc: trace.SpanContext{},
+		},
+	}
 
-	outReq, _ := http.NewRequest(http.MethodGet, "http://www.example.com", nil)
-	prop.Inject(ctx, outReq.Header)
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			inReq, _ := http.NewRequest(http.MethodGet, "http://example.com", nil)
+			for hk, hv := range tt.headers {
+				inReq.Header.Add(hk, hv)
+			}
 
-	if diff := cmp.Diff(outReq.Header.Get(headerName), want); diff != "" {
-		t.Errorf("Propagate tracestate: -got +want %s", diff)
+			ctx := prop.Extract(context.Background(), inReq.Header)
+			if diff := cmp.Diff(
+				trace.RemoteSpanContextFromContext(ctx),
+				tt.wantSc,
+				cmp.AllowUnexported(label.Value{}),
+				cmp.AllowUnexported(trace.TraceState{}),
+			); diff != "" {
+				t.Errorf("Extracted tracestate: -got +want %s", diff)
+			}
+
+			if tt.valid {
+				mockTracer := oteltest.DefaultTracer()
+				ctx, _ = mockTracer.Start(ctx, "inject")
+				outReq, _ := http.NewRequest(http.MethodGet, "http://www.example.com", nil)
+				prop.Inject(ctx, outReq.Header)
+
+				if diff := cmp.Diff(outReq.Header.Get(stateHeader), tt.headers[stateHeader]); diff != "" {
+					t.Errorf("Propagated tracestate: -got +want %s", diff)
+				}
+			}
+		})
 	}
 }