2022-11-29 21:53:28 +00:00
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// Copyright The OpenTelemetry Authors
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2024-04-11 07:46:22 +00:00
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// SPDX-License-Identifier: Apache-2.0
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2022-11-29 21:53:28 +00:00
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package propagation // import "go.opentelemetry.io/otel/propagation"
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import (
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"context"
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"encoding/hex"
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"fmt"
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"strings"
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"go.opentelemetry.io/otel/trace"
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)
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const (
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supportedVersion = 0
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maxVersion = 254
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traceparentHeader = "traceparent"
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tracestateHeader = "tracestate"
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delimiter = "-"
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)
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// TraceContext is a propagator that supports the W3C Trace Context format
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// (https://www.w3.org/TR/trace-context/)
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//
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// This propagator will propagate the traceparent and tracestate headers to
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// guarantee traces are not broken. It is up to the users of this propagator
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// to choose if they want to participate in a trace by modifying the
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// traceparent header and relevant parts of the tracestate header containing
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// their proprietary information.
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type TraceContext struct{}
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var (
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_ TextMapPropagator = TraceContext{}
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versionPart = fmt.Sprintf("%.2X", supportedVersion)
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)
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// Inject set tracecontext from the Context into the carrier.
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func (tc TraceContext) Inject(ctx context.Context, carrier TextMapCarrier) {
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sc := trace.SpanContextFromContext(ctx)
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if !sc.IsValid() {
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return
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}
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if ts := sc.TraceState().String(); ts != "" {
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carrier.Set(tracestateHeader, ts)
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}
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// Clear all flags other than the trace-context supported sampling bit.
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flags := sc.TraceFlags() & trace.FlagsSampled
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var sb strings.Builder
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sb.Grow(2 + 32 + 16 + 2 + 3)
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_, _ = sb.WriteString(versionPart)
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traceID := sc.TraceID()
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spanID := sc.SpanID()
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flagByte := [1]byte{byte(flags)}
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var buf [32]byte
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for _, src := range [][]byte{traceID[:], spanID[:], flagByte[:]} {
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_ = sb.WriteByte(delimiter[0])
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n := hex.Encode(buf[:], src)
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_, _ = sb.Write(buf[:n])
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}
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carrier.Set(traceparentHeader, sb.String())
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}
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// Extract reads tracecontext from the carrier into a returned Context.
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//
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// The returned Context will be a copy of ctx and contain the extracted
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// tracecontext as the remote SpanContext. If the extracted tracecontext is
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// invalid, the passed ctx will be returned directly instead.
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func (tc TraceContext) Extract(ctx context.Context, carrier TextMapCarrier) context.Context {
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sc := tc.extract(carrier)
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if !sc.IsValid() {
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return ctx
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}
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return trace.ContextWithRemoteSpanContext(ctx, sc)
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}
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func (tc TraceContext) extract(carrier TextMapCarrier) trace.SpanContext {
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h := carrier.Get(traceparentHeader)
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if h == "" {
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return trace.SpanContext{}
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}
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var ver [1]byte
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if !extractPart(ver[:], &h, 2) {
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return trace.SpanContext{}
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}
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version := int(ver[0])
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if version > maxVersion {
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return trace.SpanContext{}
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}
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var scc trace.SpanContextConfig
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if !extractPart(scc.TraceID[:], &h, 32) {
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return trace.SpanContext{}
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}
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if !extractPart(scc.SpanID[:], &h, 16) {
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return trace.SpanContext{}
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}
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var opts [1]byte
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if !extractPart(opts[:], &h, 2) {
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return trace.SpanContext{}
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}
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if version == 0 && (h != "" || opts[0] > 2) {
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// version 0 not allow extra
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// version 0 not allow other flag
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return trace.SpanContext{}
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}
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// Clear all flags other than the trace-context supported sampling bit.
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scc.TraceFlags = trace.TraceFlags(opts[0]) & trace.FlagsSampled
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// Ignore the error returned here. Failure to parse tracestate MUST NOT
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// affect the parsing of traceparent according to the W3C tracecontext
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// specification.
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scc.TraceState, _ = trace.ParseTraceState(carrier.Get(tracestateHeader))
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scc.Remote = true
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sc := trace.NewSpanContext(scc)
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if !sc.IsValid() {
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return trace.SpanContext{}
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}
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return sc
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}
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// upperHex detect hex is upper case Unicode characters.
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func upperHex(v string) bool {
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for _, c := range v {
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if c >= 'A' && c <= 'F' {
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return true
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}
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}
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return false
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}
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func extractPart(dst []byte, h *string, n int) bool {
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part, left, _ := strings.Cut(*h, delimiter)
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*h = left
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// hex.Decode decodes unsupported upper-case characters, so exclude explicitly.
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if len(part) != n || upperHex(part) {
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return false
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}
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if p, err := hex.Decode(dst, []byte(part)); err != nil || p != n/2 {
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return false
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}
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return true
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}
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// Fields returns the keys who's values are set with Inject.
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func (tc TraceContext) Fields() []string {
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return []string{traceparentHeader, tracestateHeader}
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}
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