| // 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" |
| "strings" |
| |
| "go.opentelemetry.io/otel/trace" |
| ) |
| |
| const ( |
| supportedVersion = 0 |
| maxVersion = 254 |
| traceparentHeader = "traceparent" |
| tracestateHeader = "tracestate" |
| delimiter = "-" |
| ) |
| |
| // 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{} |
| versionPart = fmt.Sprintf("%.2X", supportedVersion) |
| ) |
| |
| // 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 |
| |
| var sb strings.Builder |
| sb.Grow(2 + 32 + 16 + 2 + 3) |
| _, _ = sb.WriteString(versionPart) |
| traceID := sc.TraceID() |
| spanID := sc.SpanID() |
| flagByte := [1]byte{byte(flags)} |
| var buf [32]byte |
| for _, src := range [][]byte{traceID[:], spanID[:], flagByte[:]} { |
| _ = sb.WriteByte(delimiter[0]) |
| n := hex.Encode(buf[:], src) |
| _, _ = sb.Write(buf[:n]) |
| } |
| carrier.Set(traceparentHeader, sb.String()) |
| } |
| |
| // 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{} |
| } |
| |
| var ver [1]byte |
| if !extractPart(ver[:], &h, 2) { |
| return trace.SpanContext{} |
| } |
| version := int(ver[0]) |
| if version > maxVersion { |
| return trace.SpanContext{} |
| } |
| |
| var scc trace.SpanContextConfig |
| if !extractPart(scc.TraceID[:], &h, 32) { |
| return trace.SpanContext{} |
| } |
| if !extractPart(scc.SpanID[:], &h, 16) { |
| return trace.SpanContext{} |
| } |
| |
| var opts [1]byte |
| if !extractPart(opts[:], &h, 2) { |
| return trace.SpanContext{} |
| } |
| if version == 0 && (h != "" || opts[0] > 2) { |
| // version 0 not allow extra |
| // version 0 not allow other flag |
| 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 |
| } |
| |
| // upperHex detect hex is upper case Unicode characters. |
| func upperHex(v string) bool { |
| for _, c := range v { |
| if c >= 'A' && c <= 'F' { |
| return true |
| } |
| } |
| return false |
| } |
| |
| func extractPart(dst []byte, h *string, n int) bool { |
| part, left, _ := strings.Cut(*h, delimiter) |
| *h = left |
| // hex.Decode decodes unsupported upper-case characters, so exclude explicitly. |
| if len(part) != n || upperHex(part) { |
| return false |
| } |
| if p, err := hex.Decode(dst, []byte(part)); err != nil || p != n/2 { |
| return false |
| } |
| return true |
| } |
| |
| // Fields returns the keys who's values are set with Inject. |
| func (tc TraceContext) Fields() []string { |
| return []string{traceparentHeader, tracestateHeader} |
| } |