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propagation.go
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propagation.go
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// 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 zipkin
import (
"strconv"
"strings"
opentracing "github.com/opentracing/opentracing-go"
"github.com/uber/jaeger-client-go"
)
// Propagator is an Injector and Extractor
type Propagator struct{}
// NewZipkinB3HTTPHeaderPropagator creates a Propagator for extracting and injecting
// Zipkin HTTP B3 headers into SpanContexts.
func NewZipkinB3HTTPHeaderPropagator() Propagator {
return Propagator{}
}
// Inject conforms to the Injector interface for decoding Zipkin HTTP B3 headers
func (p Propagator) Inject(
sc jaeger.SpanContext,
abstractCarrier interface{},
) error {
textMapWriter, ok := abstractCarrier.(opentracing.TextMapWriter)
if !ok {
return opentracing.ErrInvalidCarrier
}
// TODO this needs to change to support 128bit IDs
textMapWriter.Set("x-b3-traceid", strconv.FormatUint(sc.TraceID().Low, 16))
if sc.ParentID() != 0 {
textMapWriter.Set("x-b3-parentspanid", strconv.FormatUint(uint64(sc.ParentID()), 16))
}
textMapWriter.Set("x-b3-spanid", strconv.FormatUint(uint64(sc.SpanID()), 16))
if sc.IsSampled() {
textMapWriter.Set("x-b3-sampled", "1")
} else {
textMapWriter.Set("x-b3-sampled", "0")
}
return nil
}
// Extract conforms to the Extractor interface for encoding Zipkin HTTP B3 headers
func (p Propagator) Extract(abstractCarrier interface{}) (jaeger.SpanContext, error) {
textMapReader, ok := abstractCarrier.(opentracing.TextMapReader)
if !ok {
return jaeger.SpanContext{}, opentracing.ErrInvalidCarrier
}
var traceID uint64
var spanID uint64
var parentID uint64
sampled := false
err := textMapReader.ForeachKey(func(rawKey, value string) error {
key := strings.ToLower(rawKey) // TODO not necessary for plain TextMap
var err error
if key == "x-b3-traceid" {
traceID, err = strconv.ParseUint(value, 16, 64)
} else if key == "x-b3-parentspanid" {
parentID, err = strconv.ParseUint(value, 16, 64)
} else if key == "x-b3-spanid" {
spanID, err = strconv.ParseUint(value, 16, 64)
} else if key == "x-b3-sampled" && value == "1" {
sampled = true
}
return err
})
if err != nil {
return jaeger.SpanContext{}, err
}
if traceID == 0 {
return jaeger.SpanContext{}, opentracing.ErrSpanContextNotFound
}
return jaeger.NewSpanContext(
jaeger.TraceID{Low: traceID},
jaeger.SpanID(spanID),
jaeger.SpanID(parentID),
sampled, nil), nil
}