PR comments

api/propagation/noop_propagator.go

@@ -18,6 +18,7 @@ import (
 	"context"
 
 	"go.opentelemetry.io/api/core"
+	dctx "go.opentelemetry.io/api/distributedcontext"
 )
 
 // NoopTextFormatPropagator implements TextFormatPropagator that does nothing.
@@ -26,12 +27,12 @@ type NoopTextFormatPropagator struct{}
 var _ TextFormatPropagator = NoopTextFormatPropagator{}
 
 // Inject does nothing.
-func (np NoopTextFormatPropagator) Inject(ctx context.Context, supplier Supplier) {
+func (np NoopTextFormatPropagator) Inject(ctx context.Context, correlationCtx dctx.Map, supplier Supplier) {
 }
 
 // Extract does nothing and returns an empty SpanContext
-func (np NoopTextFormatPropagator) Extract(ctx context.Context, supplier Supplier) core.SpanContext {
-	return core.EmptySpanContext()
+func (np NoopTextFormatPropagator) Extract(ctx context.Context, supplier Supplier) (core.SpanContext, dctx.Map) {
+	return core.EmptySpanContext(), dctx.NewEmptyMap()
 }
 
 // GetAllKeys returns empty list of strings.

api/propagation/propagator.go

@@ -18,22 +18,25 @@ import (
 	"context"
 
 	"go.opentelemetry.io/api/core"
+	dctx "go.opentelemetry.io/api/distributedcontext"
 )
 
 // TextFormatPropagator is an interface that specifies methods to inject and extract SpanContext
-// into/from a carrier using Supplier interface.
+// and distributed context into/from a carrier using Supplier interface.
 // For example, HTTP Trace Context propagator would encode SpanContext into W3C Trace
 // Context Header and set the header into HttpRequest.
 type TextFormatPropagator interface {
 	// Inject method retrieves current SpanContext from the ctx, encodes it into propagator
 	// specific format and then injects the encoded SpanContext using supplier into a carrier
-	// associated with the supplier.
-	Inject(ctx context.Context, supplier Supplier)
+	// associated with the supplier. It also takes a correlationCtx whose values will be
+	// injected into a carrier using the supplier.
+	Inject(ctx context.Context, correlationCtx dctx.Map, supplier Supplier)
 
 	// Extract method retrieves encoded SpanContext using supplier from the associated carrier.
-	// It decodes the SpanContext and returns it. If no SpanContext was retrieved OR
-	// if the retrieved SpanContext is invalid then an empty SpanContext is returned.
-	Extract(ctx context.Context, supplier Supplier) core.SpanContext
+	// It decodes the SpanContext and returns it and a dctx of correlated context.
+	// If no SpanContext was retrieved OR if the retrieved SpanContext is invalid then
+	// an empty SpanContext is returned.
+	Extract(ctx context.Context, supplier Supplier) (core.SpanContext, dctx.Map)
 
 	// GetAllKeys returns all the keys that this propagator injects/extracts into/from a
 	// carrier. The use cases for this are

plugin/httptrace/httptrace.go

@@ -19,6 +19,7 @@ import (
 	"net/http"
 
 	"go.opentelemetry.io/api/core"
+	dctx "go.opentelemetry.io/api/distributedcontext"
 	"go.opentelemetry.io/api/key"
 	"go.opentelemetry.io/propagation"
 )
@@ -36,16 +37,24 @@ var (
 
 // Returns the Attributes, Context Entries, and SpanContext that were encoded by Inject.
 func Extract(ctx context.Context, req *http.Request) ([]core.KeyValue, []core.KeyValue, core.SpanContext) {
-	sc := propagator.Extract(ctx, req.Header)
+	sc, correlationCtx := propagator.Extract(ctx, req.Header)
 
 	attrs := []core.KeyValue{
 		URLKey.String(req.URL.String()),
 		// Etc.
 	}
+	correlationCtx.Foreach(func(kv core.KeyValue) bool {
+		attrs = append(attrs, kv)
+		return true
+	})
 
 	return attrs, nil, sc
 }
 
 func Inject(ctx context.Context, req *http.Request) {
-	propagator.Inject(ctx, req.Header)
+	propagator.Inject(ctx, dctx.NewEmptyMap(), req.Header)
+}
+
+func InjectWithCorrelationCtx(ctx context.Context, correlationCtx dctx.Map, req *http.Request) {
+	propagator.Inject(ctx, correlationCtx, req.Header)
 }

plugin/othttp/server.go

@@ -18,6 +18,7 @@ import (
 	"net/http"
 
 	"go.opentelemetry.io/api/core"
+	dctx "go.opentelemetry.io/api/distributedcontext"
 	"go.opentelemetry.io/api/propagation"
 	"go.opentelemetry.io/api/trace"
 	prop "go.opentelemetry.io/propagation"
@@ -129,7 +130,8 @@ func NewHandler(handler http.Handler, operation string, opts ...HandlerOption) h
 func (h *HTTPHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	opts := append([]trace.SpanOption{}, h.spanOptions...) // start with the configured options
 
-	sc := h.prop.Extract(r.Context(), r.Header)
+	// TODO: do something with the correlation context
+	sc, _ := h.prop.Extract(r.Context(), r.Header)
 	if sc.IsValid() { // not a valid span context, so no link / parent relationship to establish
 		var opt trace.SpanOption
 		if h.public {
@@ -178,7 +180,7 @@ func (h *HTTPHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	setBeforeServeAttributes(span, r.Host, r.Method, r.URL.Path, r.URL.String(), r.UserAgent())
 	// inject the response header before calling ServeHTTP because a Write in
 	// ServeHTTP will cause all headers to be written out.
-	h.prop.Inject(ctx, rww.Header())
+	h.prop.Inject(ctx, dctx.NewEmptyMap(), rww.Header())
 
 	h.handler.ServeHTTP(rww, r.WithContext(ctx))
 	setAfterServeAttributes(span, bw.read, rww.written, int64(rww.statusCode), bw.err, rww.err)

propagation/http_b3_propagator.go

@@ -24,6 +24,7 @@ import (
 	"go.opentelemetry.io/api/trace"
 
 	"go.opentelemetry.io/api/core"
+	dctx "go.opentelemetry.io/api/distributedcontext"
 	apipropagation "go.opentelemetry.io/api/propagation"
 )
 
@@ -65,7 +66,7 @@ func HttpB3Propagator(singleHeader bool) httpB3Propagator {
 	return httpB3Propagator{singleHeader}
 }
 
-func (b3 httpB3Propagator) Inject(ctx context.Context, supplier apipropagation.Supplier) {
+func (b3 httpB3Propagator) Inject(ctx context.Context, correlationCtx dctx.Map, supplier apipropagation.Supplier) {
 	sc := trace.CurrentSpan(ctx).SpanContext()
 	if sc.IsValid() {
 		if b3.singleHeader {
@@ -90,11 +91,11 @@ func (b3 httpB3Propagator) Inject(ctx context.Context, supplier apipropagation.S
 }
 
 // Extract retrieves B3 Headers from the supplier
-func (b3 httpB3Propagator) Extract(ctx context.Context, supplier apipropagation.Supplier) core.SpanContext {
+func (b3 httpB3Propagator) Extract(ctx context.Context, supplier apipropagation.Supplier) (core.SpanContext, dctx.Map) {
 	if b3.singleHeader {
-		return b3.extractSingleHeader(supplier)
+		return b3.extractSingleHeader(supplier), dctx.NewEmptyMap()
 	}
-	return b3.extract(supplier)
+	return b3.extract(supplier), dctx.NewEmptyMap()
 }
 
 func (b3 httpB3Propagator) GetAllKeys() []string {

propagation/http_b3_propagator_benchmark_test.go

@@ -19,6 +19,7 @@ import (
 	"net/http"
 	"testing"
 
+	dctx "go.opentelemetry.io/api/distributedcontext"
 	"go.opentelemetry.io/api/trace"
 	mocktrace "go.opentelemetry.io/internal/trace"
 	"go.opentelemetry.io/propagation"
@@ -65,7 +66,7 @@ func BenchmarkExtractB3(b *testing.B) {
 				b.ReportAllocs()
 				b.ResetTimer()
 				for i := 0; i < b.N; i++ {
-					_ = propagator.Extract(ctx, req.Header)
+					_, _ = propagator.Extract(ctx, req.Header)
 				}
 			})
 		}
@@ -112,7 +113,7 @@ func BenchmarkInjectB3(b *testing.B) {
 				b.ReportAllocs()
 				b.ResetTimer()
 				for i := 0; i < b.N; i++ {
-					propagator.Inject(ctx, req.Header)
+					propagator.Inject(ctx, dctx.NewEmptyMap(), req.Header)
 				}
 			})
 		}

propagation/http_b3_propagator_test.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/google/go-cmp/cmp"
 
+	dctx "go.opentelemetry.io/api/distributedcontext"
 	"go.opentelemetry.io/api/trace"
 	mocktrace "go.opentelemetry.io/internal/trace"
 	"go.opentelemetry.io/propagation"
@@ -65,7 +66,7 @@ func TestExtractB3(t *testing.T) {
 				}
 
 				ctx := context.Background()
-				gotSc := propagator.Extract(ctx, req.Header)
+				gotSc, _ := propagator.Extract(ctx, req.Header)
 				if diff := cmp.Diff(gotSc, tt.wantSc); diff != "" {
 					t.Errorf("%s: %s: -got +want %s", tg.name, tt.name, diff)
 				}
@@ -111,7 +112,7 @@ func TestInjectB3(t *testing.T) {
 				} else {
 					ctx, _ = mockTracer.Start(ctx, "inject")
 				}
-				propagator.Inject(ctx, req.Header)
+				propagator.Inject(ctx, dctx.NewEmptyMap(), req.Header)
 
 				for h, v := range tt.wantHeaders {
 					got, want := req.Header.Get(h), v