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123 lines
3.6 KiB
Go
123 lines
3.6 KiB
Go
// Copyright 2018, OpenCensus Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package b3 contains a propagation.HTTPFormat implementation
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// for B3 propagation. See https://github.com/openzipkin/b3-propagation
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// for more details.
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package b3 // import "go.opencensus.io/plugin/ochttp/propagation/b3"
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import (
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"encoding/hex"
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"net/http"
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"go.opencensus.io/trace"
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"go.opencensus.io/trace/propagation"
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)
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// B3 headers that OpenCensus understands.
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const (
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TraceIDHeader = "X-B3-TraceId"
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SpanIDHeader = "X-B3-SpanId"
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SampledHeader = "X-B3-Sampled"
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)
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// HTTPFormat implements propagation.HTTPFormat to propagate
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// traces in HTTP headers in B3 propagation format.
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// HTTPFormat skips the X-B3-ParentId and X-B3-Flags headers
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// because there are additional fields not represented in the
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// OpenCensus span context. Spans created from the incoming
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// header will be the direct children of the client-side span.
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// Similarly, receiver of the outgoing spans should use client-side
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// span created by OpenCensus as the parent.
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type HTTPFormat struct{}
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var _ propagation.HTTPFormat = (*HTTPFormat)(nil)
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// SpanContextFromRequest extracts a B3 span context from incoming requests.
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func (f *HTTPFormat) SpanContextFromRequest(req *http.Request) (sc trace.SpanContext, ok bool) {
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tid, ok := ParseTraceID(req.Header.Get(TraceIDHeader))
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if !ok {
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return trace.SpanContext{}, false
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}
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sid, ok := ParseSpanID(req.Header.Get(SpanIDHeader))
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if !ok {
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return trace.SpanContext{}, false
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}
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sampled, _ := ParseSampled(req.Header.Get(SampledHeader))
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return trace.SpanContext{
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TraceID: tid,
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SpanID: sid,
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TraceOptions: sampled,
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}, true
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}
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// ParseTraceID parses the value of the X-B3-TraceId header.
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func ParseTraceID(tid string) (trace.TraceID, bool) {
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if tid == "" {
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return trace.TraceID{}, false
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}
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b, err := hex.DecodeString(tid)
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if err != nil || len(b) > 16 {
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return trace.TraceID{}, false
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}
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var traceID trace.TraceID
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if len(b) <= 8 {
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// The lower 64-bits.
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start := 8 + (8 - len(b))
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copy(traceID[start:], b)
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} else {
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start := 16 - len(b)
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copy(traceID[start:], b)
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}
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return traceID, true
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}
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// ParseSpanID parses the value of the X-B3-SpanId or X-B3-ParentSpanId headers.
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func ParseSpanID(sid string) (spanID trace.SpanID, ok bool) {
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if sid == "" {
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return trace.SpanID{}, false
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}
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b, err := hex.DecodeString(sid)
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if err != nil || len(b) > 8 {
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return trace.SpanID{}, false
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}
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start := 8 - len(b)
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copy(spanID[start:], b)
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return spanID, true
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}
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// ParseSampled parses the value of the X-B3-Sampled header.
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func ParseSampled(sampled string) (trace.TraceOptions, bool) {
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switch sampled {
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case "true", "1":
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return trace.TraceOptions(1), true
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default:
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return trace.TraceOptions(0), false
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}
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}
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// SpanContextToRequest modifies the given request to include B3 headers.
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func (f *HTTPFormat) SpanContextToRequest(sc trace.SpanContext, req *http.Request) {
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req.Header.Set(TraceIDHeader, hex.EncodeToString(sc.TraceID[:]))
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req.Header.Set(SpanIDHeader, hex.EncodeToString(sc.SpanID[:]))
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var sampled string
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if sc.IsSampled() {
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sampled = "1"
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} else {
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sampled = "0"
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}
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req.Header.Set(SampledHeader, sampled)
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}
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