Checkpoint

api/context/propagation/propagation.go

@@ -0,0 +1,103 @@
+// 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 propagation
+
+import (
+	"context"
+	"sync/atomic"
+
+	"go.opentelemetry.io/otel/api/core"
+)
+
+// HTTPSupplier is implemented by http.Headers.
+type HTTPSupplier interface {
+	Get(key string) string
+	Set(key string, value string)
+}
+
+type HTTPExtractor interface {
+	// Extract method retrieves encoded SpanContext using supplier
+	// from the associated carrier.  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(context.Context, HTTPSupplier) (core.SpanContext, dctx.Map)
+}
+
+type HTTPInjector 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. It also takes a
+	// correlationCtx whose values will be injected into a carrier
+	// using the supplier.
+	Inject(context.Context, HTTPSupplier) context.Context
+}
+
+type Propagators interface {
+	// HTTP propagation
+	SetHTTPExtractors(...HTTPExtractor)
+	SetHTTPInjectors(...HTTPInjector)
+	HTTPExtractors() []HTTPExtractor
+	HTTPInjectors() []HTTPInjector
+
+	// Binary propagation
+	// TODO
+}
+
+type propagators struct {
+	// TODO Nah.  Use an options pattern to avoid mutation.
+
+	httpEx atomic.Value // []HTTPExtractor
+	httpIn atomic.Value // []HTTPInjector
+}
+
+func New() Propagators {
+	p := &propagators{}
+
+	p.httpIn.Store([]HTTPInjector{})
+	p.httpEs.Store([]HTTPExtractor{})
+
+	return p
+}
+
+func (p *Propagators) SetHTTPExtractors(ex ...HTTPExtractor) {
+	if ex == nil {
+		ex = []HTTPExtractor{}
+	}
+	p.httpEx.Store(ex)
+}
+
+func (p *Propagators) SetHTTPInjectors(in ...HTTPInjector) {
+	if in == nil {
+		in = []HTTPInjector{}
+	}
+	p.httpIn.Store(in)
+}
+
+func (p *Propagators) HTTPExtractors() []HTTPExtractor {
+	return p.httpEx.Load().([]HTTPExtractor)
+}
+
+func (p *Propagators) HTTPInjectors() []HTTPInjector {
+	return p.httpIn.Load().([]HTTPInjector)
+}
+
+type NoopPropagators struct{}
+
+func (NoopPropagators) SetHTTPExtractors(ex ...HTTPExtractor) {}
+func (NoopPropagators) SetHTTPInjectors(in ...HTTPInjector)   {}
+func (NoopPropagators) HTTPExtractors() []HTTPExtractor       { return nil }
+func (NoopPropagators) HTTPInjectors() []HTTPInjector         { return nil }

api/global/global.go

@@ -17,6 +17,7 @@ package global
 import (
 	"sync/atomic"
 
+	"go.opentelemetry.io/otel/api/context/propagation"
 	"go.opentelemetry.io/otel/api/metric"
 	"go.opentelemetry.io/otel/api/trace"
 )
@@ -29,11 +30,16 @@ type (
 	meterProvider struct {
 		mp metric.Provider
 	}
+
+	propagators struct {
+		pr propagation.Propagators
+	}
 )
 
 var (
-	globalTracer atomic.Value
-	globalMeter  atomic.Value
+	globalTracer      atomic.Value
+	globalMeter       atomic.Value
+	globalPropagators atomic.Value
 )
 
 // TraceProvider returns the registered global trace provider.
@@ -67,3 +73,18 @@ func MeterProvider() metric.Provider {
 func SetMeterProvider(mp metric.Provider) {
 	globalMeter.Store(meterProvider{mp: mp})
 }
+
+// Propagators returns the registered global propagators instance.  If
+// none is registered then an instance of propagators.NoopPropagators
+// is returned.
+func Propagators() propagation.Propagators {
+	if gp := globalPropagators.Load(); gp != nil {
+		return gp.(propagators).prop
+	}
+	return propagation.NoopPropagators{}
+}
+
+// SetPropagators registers `p` as the global propagators instance.
+func SetPropagators(p Propagators) {
+	globalPropagators.Store(propatators{prop: p})
+}

go.sum

@@ -284,6 +284,7 @@ github.com/valyala/tcplisten v0.0.0-20161114210144-ceec8f93295a/go.mod h1:v3UYOV
 github.com/xiang90/probing v0.0.0-20190116061207-43a291ad63a2/go.mod h1:UETIi67q53MR2AWcXfiuqkDkRtnGDLqkBTpCHuJHxtU=
 github.com/xordataexchange/crypt v0.0.3-0.20170626215501-b2862e3d0a77/go.mod h1:aYKd//L2LvnjZzWKhF00oedf4jCCReLcmhLdhm1A27Q=
 go.etcd.io/bbolt v1.3.2/go.mod h1:IbVyRI1SCnLcuJnV2u8VeU0CEYM7e686BmAb1XKL+uU=
+go.opentelemetry.io v0.1.0 h1:EANZoRCOP+A3faIlw/iN6YEWoYb1vleZRKm1EvH8T48=
 go.uber.org/atomic v1.4.0/go.mod h1:gD2HeocX3+yG+ygLZcrzQJaqmWj9AIm7n08wl/qW/PE=
 go.uber.org/multierr v1.1.0/go.mod h1:wR5kodmAFQ0UK8QlbwjlSNy0Z68gJhDJUG5sjR94q/0=
 go.uber.org/zap v1.10.0/go.mod h1:vwi/ZaCAaUcBkycHslxD9B2zi4UTXhF60s6SWpuDF0Q=