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| 1 | +package xxray |
| 2 | + |
| 3 | +import ( |
| 4 | + "context" |
| 5 | + "errors" |
| 6 | + "strings" |
| 7 | + |
| 8 | + "go.opentelemetry.io/contrib/propagators/aws/xray" |
| 9 | + "go.opentelemetry.io/otel/propagation" |
| 10 | + "go.opentelemetry.io/otel/trace" |
| 11 | +) |
| 12 | + |
| 13 | +// Propagator is an AWS X-Ray trace propagator that extends the standard [xray.Propagator]. |
| 14 | +// Standard propagator requires both Root and Parent keys to be present in the X-Amzn-Trace-Id header |
| 15 | +// to successfully extract span context. |
| 16 | +// AWS [ALB request tracing] creates X-Amzn-Trace-Id header with only Root field - this propagator |
| 17 | +// can re-use it to obtain trace ID value. |
| 18 | +// |
| 19 | +// [ALB request tracing]: https://docs.aws.amazon.com/elasticloadbalancing/latest/application/load-balancer-request-tracing.html |
| 20 | +type Propagator struct { |
| 21 | + xray.Propagator |
| 22 | + idGenerator *xray.IDGenerator |
| 23 | +} |
| 24 | + |
| 25 | +func NewPropagator() *Propagator { |
| 26 | + return &Propagator{idGenerator: xray.NewIDGenerator()} |
| 27 | +} |
| 28 | + |
| 29 | +func (p *Propagator) Extract(ctx context.Context, carrier propagation.TextMapCarrier) context.Context { |
| 30 | + newCtx := p.Propagator.Extract(ctx, carrier) |
| 31 | + // If failed to extract span context, try to re-use trace id |
| 32 | + if newCtx == ctx { |
| 33 | + if header := carrier.Get(traceHeaderKey); header != "" { |
| 34 | + tsc, err := extract(header) |
| 35 | + if err == nil && tsc.TraceID().IsValid() { |
| 36 | + // Re-use only trace id |
| 37 | + return trace.ContextWithRemoteSpanContext(ctx, trace.NewSpanContext(trace.SpanContextConfig{ |
| 38 | + TraceID: tsc.TraceID(), |
| 39 | + SpanID: p.idGenerator.NewSpanID(ctx, tsc.TraceID()), |
| 40 | + })) |
| 41 | + } |
| 42 | + } |
| 43 | + } |
| 44 | + return newCtx |
| 45 | +} |
| 46 | + |
| 47 | +// The rest is copied from https://github.com/open-telemetry/opentelemetry-go-contrib/blob/80c9316336ebb4f4c67d8e1011a3add889213fb7/propagators/aws/xray/propagator.go |
| 48 | +const ( |
| 49 | + traceHeaderKey = "X-Amzn-Trace-Id" |
| 50 | + traceHeaderDelimiter = ";" |
| 51 | + kvDelimiter = "=" |
| 52 | + traceIDKey = "Root" |
| 53 | + sampleFlagKey = "Sampled" |
| 54 | + parentIDKey = "Parent" |
| 55 | + traceIDVersion = "1" |
| 56 | + traceIDDelimiter = "-" |
| 57 | + isSampled = "1" |
| 58 | + notSampled = "0" |
| 59 | + |
| 60 | + traceFlagNone = 0x0 |
| 61 | + traceFlagSampled = 0x1 << 0 |
| 62 | + traceIDLength = 35 |
| 63 | + traceIDDelimitterIndex1 = 1 |
| 64 | + traceIDDelimitterIndex2 = 10 |
| 65 | + traceIDFirstPartLength = 8 |
| 66 | + sampledFlagLength = 1 |
| 67 | +) |
| 68 | + |
| 69 | +var ( |
| 70 | + empty = trace.SpanContext{} |
| 71 | + errInvalidTraceHeader = errors.New("invalid X-Amzn-Trace-Id header value, should contain 3 different part separated by ;") |
| 72 | + errMalformedTraceID = errors.New("cannot decode trace ID from header") |
| 73 | + errLengthTraceIDHeader = errors.New("incorrect length of X-Ray trace ID found, 35 character length expected") |
| 74 | + errInvalidTraceIDVersion = errors.New("invalid X-Ray trace ID header found, does not have valid trace ID version") |
| 75 | + errInvalidSpanIDLength = errors.New("invalid span ID length, must be 16") |
| 76 | +) |
| 77 | + |
| 78 | +// extract extracts Span Context from context. |
| 79 | +func extract(headerVal string) (trace.SpanContext, error) { |
| 80 | + var ( |
| 81 | + scc = trace.SpanContextConfig{} |
| 82 | + err error |
| 83 | + delimiterIndex int |
| 84 | + part string |
| 85 | + ) |
| 86 | + pos := 0 |
| 87 | + for pos < len(headerVal) { |
| 88 | + delimiterIndex = indexOf(headerVal, traceHeaderDelimiter, pos) |
| 89 | + if delimiterIndex >= 0 { |
| 90 | + part = headerVal[pos:delimiterIndex] |
| 91 | + pos = delimiterIndex + 1 |
| 92 | + } else { |
| 93 | + // last part |
| 94 | + part = strings.TrimSpace(headerVal[pos:]) |
| 95 | + pos = len(headerVal) |
| 96 | + } |
| 97 | + equalsIndex := strings.Index(part, kvDelimiter) |
| 98 | + if equalsIndex < 0 { |
| 99 | + return empty, errInvalidTraceHeader |
| 100 | + } |
| 101 | + value := part[equalsIndex+1:] |
| 102 | + switch { |
| 103 | + case strings.HasPrefix(part, traceIDKey): |
| 104 | + scc.TraceID, err = parseTraceID(value) |
| 105 | + if err != nil { |
| 106 | + return empty, err |
| 107 | + } |
| 108 | + case strings.HasPrefix(part, parentIDKey): |
| 109 | + // extract parentId |
| 110 | + scc.SpanID, err = trace.SpanIDFromHex(value) |
| 111 | + if err != nil { |
| 112 | + return empty, errInvalidSpanIDLength |
| 113 | + } |
| 114 | + case strings.HasPrefix(part, sampleFlagKey): |
| 115 | + // extract traceflag |
| 116 | + scc.TraceFlags = parseTraceFlag(value) |
| 117 | + } |
| 118 | + } |
| 119 | + return trace.NewSpanContext(scc), nil |
| 120 | +} |
| 121 | + |
| 122 | +// indexOf returns position of the first occurrence of a substr in str starting at pos index. |
| 123 | +func indexOf(str, substr string, pos int) int { |
| 124 | + index := strings.Index(str[pos:], substr) |
| 125 | + if index > -1 { |
| 126 | + index += pos |
| 127 | + } |
| 128 | + return index |
| 129 | +} |
| 130 | + |
| 131 | +// parseTraceID returns trace ID if valid else return invalid trace ID. |
| 132 | +func parseTraceID(xrayTraceID string) (trace.TraceID, error) { |
| 133 | + if len(xrayTraceID) != traceIDLength { |
| 134 | + return empty.TraceID(), errLengthTraceIDHeader |
| 135 | + } |
| 136 | + if !strings.HasPrefix(xrayTraceID, traceIDVersion) { |
| 137 | + return empty.TraceID(), errInvalidTraceIDVersion |
| 138 | + } |
| 139 | + |
| 140 | + if xrayTraceID[traceIDDelimitterIndex1:traceIDDelimitterIndex1+1] != traceIDDelimiter || |
| 141 | + xrayTraceID[traceIDDelimitterIndex2:traceIDDelimitterIndex2+1] != traceIDDelimiter { |
| 142 | + return empty.TraceID(), errMalformedTraceID |
| 143 | + } |
| 144 | + |
| 145 | + epochPart := xrayTraceID[traceIDDelimitterIndex1+1 : traceIDDelimitterIndex2] |
| 146 | + uniquePart := xrayTraceID[traceIDDelimitterIndex2+1 : traceIDLength] |
| 147 | + |
| 148 | + result := epochPart + uniquePart |
| 149 | + return trace.TraceIDFromHex(result) |
| 150 | +} |
| 151 | + |
| 152 | +// parseTraceFlag returns a parsed trace flag. |
| 153 | +func parseTraceFlag(xraySampledFlag string) trace.TraceFlags { |
| 154 | + // Use a direct comparison here (#7262). |
| 155 | + if xraySampledFlag == isSampled { |
| 156 | + return trace.FlagsSampled |
| 157 | + } |
| 158 | + return trace.FlagsSampled.WithSampled(false) |
| 159 | +} |
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