forked from census-instrumentation/opencensus-go
/
propagation.go
101 lines (87 loc) · 2.74 KB
/
propagation.go
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// Copyright 2018, OpenCensus 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 tracecontext // import "go.opencensus.io/plugin/ochttp/propagation/tracecontext"
import (
"encoding/hex"
"fmt"
"net/http"
"strings"
"go.opencensus.io/trace"
"go.opencensus.io/trace/propagation"
)
const (
supportedVersion = 0
maxVersion = 254
header = "traceparent"
)
var _ propagation.HTTPFormat = (*HTTPFormat)(nil)
// HTTPFormat implements the TraceContext trace propagation format.
type HTTPFormat struct{}
// SpanContextFromRequest extracts a span context from incoming requests.
func (f *HTTPFormat) SpanContextFromRequest(req *http.Request) (sc trace.SpanContext, ok bool) {
h := req.Header.Get(header)
if h == "" {
return trace.SpanContext{}, false
}
sections := strings.Split(h, "-")
if len(sections) < 3 {
return trace.SpanContext{}, false
}
ver, err := hex.DecodeString(sections[0])
if err != nil {
return trace.SpanContext{}, false
}
if len(ver) == 0 || int(ver[0]) > supportedVersion || int(ver[0]) > maxVersion {
return trace.SpanContext{}, false
}
tid, err := hex.DecodeString(sections[1])
if err != nil {
return trace.SpanContext{}, false
}
if len(tid) != 16 {
return trace.SpanContext{}, false
}
copy(sc.TraceID[:], tid)
sid, err := hex.DecodeString(sections[2])
if err != nil {
return trace.SpanContext{}, false
}
if len(sid) != 8 {
return trace.SpanContext{}, false
}
copy(sc.SpanID[:], sid)
if len(sections) == 4 {
opts, err := hex.DecodeString(sections[3])
if err != nil || len(opts) < 1 {
return trace.SpanContext{}, false
}
sc.TraceOptions = trace.TraceOptions(opts[0])
}
// Don't allow all zero trace or span ID.
if sc.TraceID == [16]byte{} || sc.SpanID == [8]byte{} {
return trace.SpanContext{}, false
}
return sc, true
}
// SpanContextToRequest modifies the given request to include a header.
func (f *HTTPFormat) SpanContextToRequest(sc trace.SpanContext, req *http.Request) {
h := fmt.Sprintf("%x-%x-%x-%x",
[]byte{supportedVersion},
sc.TraceID[:],
sc.SpanID[:],
[]byte{byte(sc.TraceOptions)})
req.Header.Set(header, h)
}