move inject/extract out of trace.

api/propagation/propagator.go

@@ -0,0 +1,50 @@
+// Copyright 2019, OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package tracecontext contains HTTP propagator for TraceContext standard.
+// See https://github.com/w3c/distributed-tracing for more information.
+package propagation // import "go.opentelemetry.io/api/propagation"
+
+import (
+	"net/http"
+
+	"go.opentelemetry.io/api/core"
+	"go.opentelemetry.io/api/tag"
+)
+
+// TextFormatPropagator is an interface that specifies methods to create Injector
+// and Extractor objects. Injector object implements Inject method to inject
+// SpanContext and tag.Map as a text format into carrier like HTTP request. Similarly,
+// Extractor object implements Extract method to extract SpanContext encoded in text
+// format from a carrier like HTTP request.
+// Typically, a plugin for transport like HTTP uses this interface to allow user
+// to configure appropriate propagators.
+type TextFormatPropagator interface {
+	Extractor(req *http.Request) Extractor
+	Injector(req *http.Request) Injector
+}
+
+type Injector interface {
+	// Inject serializes span context and tag.Map and inserts them in to
+	// carrier associated with the injector. For example in case of http request,
+	// span context could be added to the request (carrier) as W3C Trace context header.
+	Inject(core.SpanContext, tag.Map)
+}
+
+type Extractor interface {
+	// Extract de-serializes span context and tag.Map from a carrier associated with the
+	// extractor. For example in case of http request, span context could be extracted
+	// from the W3C Trace context header.
+	Extract() (core.SpanContext, tag.Map)
+}

api/trace/api.go

@@ -45,9 +45,6 @@ type Tracer interface {
 
 	// WithResources attaches resource attributes to the Tracer.
 	WithResources(res ...core.KeyValue) Tracer
-
-	// Note: see https://github.com/opentracing/opentracing-go/issues/127
-	Inject(context.Context, Span, Injector)
 }
 
 type Span interface {
@@ -83,20 +80,6 @@ type Span interface {
 	ModifyAttributes(...tag.Mutator)
 }
 
-type Injector interface {
-	// Inject serializes span context and tag.Map and inserts them in to
-	// carrier associated with the injector. For example in case of http request,
-	// span context could added to the request (carrier) as W3C Trace context header.
-	Inject(core.SpanContext, tag.Map)
-}
-
-type Extractor interface {
-	// Extract deserializes span context and tag.Map from a carrier associated with the
-	// extractor. For example in case of http request, span context could be extracted
-	// from the W3C Trace context header.
-	Extract() (core.SpanContext, tag.Map)
-}
-
 // SpanOption apply changes to SpanOptions.
 type SpanOption func(*SpanOptions)
 
@@ -129,18 +112,6 @@ func Start(ctx context.Context, name string, opts ...SpanOption) (context.Contex
 	return GlobalTracer().Start(ctx, name, opts...)
 }
 
-// Inject is convenient function to inject current span context using injector.
-// Injector is expected to serialize span context and inject it in to a carrier.
-// An example of a carrier is http request.
-func Inject(ctx context.Context, injector Injector) {
-	span := CurrentSpan(ctx)
-	if span == nil {
-		return
-	}
-
-	span.Tracer().Inject(ctx, span, injector)
-}
-
 // WithStartTime sets the start time of the span to provided time t, when it is started.
 // In absensce of this option, wall clock time is used as start time.
 // This option is typically used when starting of the span is delayed.

api/trace/noop_trace.go

@@ -49,7 +49,3 @@ func (noopTracer) Start(ctx context.Context, name string, opts ...SpanOption) (c
 	span := noopSpan{}
 	return SetCurrentSpan(ctx, span), span
 }
-
-// Inject does nothing.
-func (noopTracer) Inject(ctx context.Context, span Span, injector Injector) {
-}

example/http/client/client.go

@@ -52,7 +52,7 @@ func main() {
 
 			ctx, req, inj := httptrace.W3C(ctx, req)
 
-			trace.Inject(ctx, inj)
+			inj.Inject(trace.CurrentSpan(ctx).SpanContext(), nil)
 
 			res, err := client.Do(req)
 			if err != nil {

experimental/streaming/sdk/trace.go

@@ -20,7 +20,6 @@ import (
 
 	"go.opentelemetry.io/api/core"
 	"go.opentelemetry.io/api/key"
-	"go.opentelemetry.io/api/tag"
 	"go.opentelemetry.io/api/trace"
 	apitrace "go.opentelemetry.io/api/trace"
 	"go.opentelemetry.io/experimental/streaming/exporter/observer"
@@ -127,7 +126,3 @@ func (t *tracer) Start(ctx context.Context, name string, opts ...apitrace.SpanOp
 	}
 	return trace.SetCurrentSpan(ctx, span), span
 }
-
-func (t *tracer) Inject(ctx context.Context, span apitrace.Span, injector apitrace.Injector) {
-	injector.Inject(span.SpanContext(), tag.FromContext(ctx))
-}

plugin/httptrace/api.go

@@ -19,11 +19,11 @@ import (
 	"net/http"
 	"net/http/httptrace"
 
-	"go.opentelemetry.io/api/trace"
+	"go.opentelemetry.io/api/propagation"
 )
 
 // Client
-func W3C(ctx context.Context, req *http.Request) (context.Context, *http.Request, trace.Injector) {
+func W3C(ctx context.Context, req *http.Request) (context.Context, *http.Request, propagation.Injector) {
 	t := newClientTracer(ctx)
 
 	t.GetConn = t.getConn

propagation/http_textformat_propagator.go

@@ -25,8 +25,8 @@ import (
 	"strings"
 
 	"go.opentelemetry.io/api/core"
+	apipropagation "go.opentelemetry.io/api/propagation"
 	"go.opentelemetry.io/api/tag"
-	"go.opentelemetry.io/api/trace"
 )
 
 const (
@@ -37,13 +37,13 @@ const (
 
 type textFormatPropagator struct{}
 
-var _ HTTPPropagator = textFormatPropagator{}
+var _ apipropagation.TextFormatPropagator = textFormatPropagator{}
 
-func (t textFormatPropagator) Extractor(req *http.Request) trace.Extractor {
+func (t textFormatPropagator) Extractor(req *http.Request) apipropagation.Extractor {
 	return textFormatExtractor{req: req}
 }
 
-func (t textFormatPropagator) Injector(req *http.Request) trace.Injector {
+func (t textFormatPropagator) Injector(req *http.Request) apipropagation.Injector {
 	return textFormatInjector{req: req}
 }
 
@@ -61,7 +61,7 @@ type textFormatExtractor struct {
 	req *http.Request
 }
 
-var _ trace.Extractor = textFormatExtractor{}
+var _ apipropagation.Extractor = textFormatExtractor{}
 
 // Extract implements Extract method of trace.Extractor interface. It extracts
 // W3C TraceContext Header and decodes SpanContext from the Header.
@@ -134,7 +134,7 @@ type textFormatInjector struct {
 	req *http.Request
 }
 
-var _ trace.Injector = textFormatInjector{}
+var _ apipropagation.Injector = textFormatInjector{}
 
 // Inject implements Inject method of trace.Injector interface. It encodes
 // SpanContext into W3C TraceContext Header and injects the header into

sdk/trace/tracer.go

@@ -92,7 +92,3 @@ func (tr *tracer) WithComponent(component string) apitrace.Tracer {
 	tr.component = component
 	return tr
 }
-
-func (tr *tracer) Inject(ctx context.Context, span apitrace.Span, injector apitrace.Injector) {
-	injector.Inject(span.SpanContext(), nil)
-}