swarm: integrate OpenTracing; propagate ctx to internal APIs (#17169)

* swarm: propagate ctx, enable opentracing

* swarm/tracing: log error when tracing is misconfigured

vendor/github.com/uber/jaeger-client-go/zipkin.go

@@ -0,0 +1,76 @@
+// Copyright (c) 2017 Uber Technologies, Inc.
+//
+// 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 jaeger
+
+import (
+	"github.com/opentracing/opentracing-go"
+)
+
+// ZipkinSpanFormat is an OpenTracing carrier format constant
+const ZipkinSpanFormat = "zipkin-span-format"
+
+// ExtractableZipkinSpan is a type of Carrier used for integration with Zipkin-aware
+// RPC frameworks (like TChannel). It does not support baggage, only trace IDs.
+type ExtractableZipkinSpan interface {
+	TraceID() uint64
+	SpanID() uint64
+	ParentID() uint64
+	Flags() byte
+}
+
+// InjectableZipkinSpan is a type of Carrier used for integration with Zipkin-aware
+// RPC frameworks (like TChannel). It does not support baggage, only trace IDs.
+type InjectableZipkinSpan interface {
+	SetTraceID(traceID uint64)
+	SetSpanID(spanID uint64)
+	SetParentID(parentID uint64)
+	SetFlags(flags byte)
+}
+
+type zipkinPropagator struct {
+	tracer *Tracer
+}
+
+func (p *zipkinPropagator) Inject(
+	ctx SpanContext,
+	abstractCarrier interface{},
+) error {
+	carrier, ok := abstractCarrier.(InjectableZipkinSpan)
+	if !ok {
+		return opentracing.ErrInvalidCarrier
+	}
+
+	carrier.SetTraceID(ctx.TraceID().Low) // TODO this cannot work with 128bit IDs
+	carrier.SetSpanID(uint64(ctx.SpanID()))
+	carrier.SetParentID(uint64(ctx.ParentID()))
+	carrier.SetFlags(ctx.flags)
+	return nil
+}
+
+func (p *zipkinPropagator) Extract(abstractCarrier interface{}) (SpanContext, error) {
+	carrier, ok := abstractCarrier.(ExtractableZipkinSpan)
+	if !ok {
+		return emptyContext, opentracing.ErrInvalidCarrier
+	}
+	if carrier.TraceID() == 0 {
+		return emptyContext, opentracing.ErrSpanContextNotFound
+	}
+	var ctx SpanContext
+	ctx.traceID.Low = carrier.TraceID()
+	ctx.spanID = SpanID(carrier.SpanID())
+	ctx.parentID = SpanID(carrier.ParentID())
+	ctx.flags = carrier.Flags()
+	return ctx, nil
+}