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// Copyright The 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 "go.opentelemetry.io/otel/propagation"
import (
"context"
"encoding/hex"
"fmt"
"regexp"
"go.opentelemetry.io/otel/trace"
)
const (
supportedVersion = 0
maxVersion = 254
traceparentHeader = "traceparent"
tracestateHeader = "tracestate"
)
// TraceContext is a propagator that supports the W3C Trace Context format
// (https://www.w3.org/TR/trace-context/)
//
// This propagator will propagate the traceparent and tracestate headers to
// guarantee traces are not broken. It is up to the users of this propagator
// to choose if they want to participate in a trace by modifying the
// traceparent header and relevant parts of the tracestate header containing
// their proprietary information.
type TraceContext struct{}
var _ TextMapPropagator = TraceContext{}
var traceCtxRegExp = regexp.MustCompile("^(?P<version>[0-9a-f]{2})-(?P<traceID>[a-f0-9]{32})-(?P<spanID>[a-f0-9]{16})-(?P<traceFlags>[a-f0-9]{2})(?:-.*)?$")
// Inject set tracecontext from the Context into the carrier.
func (tc TraceContext) Inject(ctx context.Context, carrier TextMapCarrier) {
sc := trace.SpanContextFromContext(ctx)
if !sc.IsValid() {
return
}
if ts := sc.TraceState().String(); ts != "" {
carrier.Set(tracestateHeader, ts)
}
// Clear all flags other than the trace-context supported sampling bit.
flags := sc.TraceFlags() & trace.FlagsSampled
h := fmt.Sprintf("%.2x-%s-%s-%s",
supportedVersion,
sc.TraceID(),
sc.SpanID(),
flags)
carrier.Set(traceparentHeader, h)
}
// Extract reads tracecontext from the carrier into a returned Context.
//
// The returned Context will be a copy of ctx and contain the extracted
// tracecontext as the remote SpanContext. If the extracted tracecontext is
// invalid, the passed ctx will be returned directly instead.
func (tc TraceContext) Extract(ctx context.Context, carrier TextMapCarrier) context.Context {
sc := tc.extract(carrier)
if !sc.IsValid() {
return ctx
}
return trace.ContextWithRemoteSpanContext(ctx, sc)
}
func (tc TraceContext) extract(carrier TextMapCarrier) trace.SpanContext {
h := carrier.Get(traceparentHeader)
if h == "" {
return trace.SpanContext{}
}
matches := traceCtxRegExp.FindStringSubmatch(h)
if len(matches) == 0 {
return trace.SpanContext{}
}
if len(matches) < 5 { // four subgroups plus the overall match
return trace.SpanContext{}
}
if len(matches[1]) != 2 {
return trace.SpanContext{}
}
ver, err := hex.DecodeString(matches[1])
if err != nil {
return trace.SpanContext{}
}
version := int(ver[0])
if version > maxVersion {
return trace.SpanContext{}
}
if version == 0 && len(matches) != 5 { // four subgroups plus the overall match
return trace.SpanContext{}
}
if len(matches[2]) != 32 {
return trace.SpanContext{}
}
var scc trace.SpanContextConfig
scc.TraceID, err = trace.TraceIDFromHex(matches[2][:32])
if err != nil {
return trace.SpanContext{}
}
if len(matches[3]) != 16 {
return trace.SpanContext{}
}
scc.SpanID, err = trace.SpanIDFromHex(matches[3])
if err != nil {
return trace.SpanContext{}
}
if len(matches[4]) != 2 {
return trace.SpanContext{}
}
opts, err := hex.DecodeString(matches[4])
if err != nil || len(opts) < 1 || (version == 0 && opts[0] > 2) {
return trace.SpanContext{}
}
// Clear all flags other than the trace-context supported sampling bit.
scc.TraceFlags = trace.TraceFlags(opts[0]) & trace.FlagsSampled
// Ignore the error returned here. Failure to parse tracestate MUST NOT
// affect the parsing of traceparent according to the W3C tracecontext
// specification.
scc.TraceState, _ = trace.ParseTraceState(carrier.Get(tracestateHeader))
scc.Remote = true
sc := trace.NewSpanContext(scc)
if !sc.IsValid() {
return trace.SpanContext{}
}
return sc
}
// Fields returns the keys who's values are set with Inject.
func (tc TraceContext) Fields() []string {
return []string{traceparentHeader, tracestateHeader}
}
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