mirror of
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108 lines
3.2 KiB
Go
108 lines
3.2 KiB
Go
// Copyright 2017, OpenCensus Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package propagation implements the binary trace context format.
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package propagation // import "go.opencensus.io/trace/propagation"
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// TODO: link to external spec document.
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// BinaryFormat format:
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//
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// Binary value: <version_id><version_format>
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// version_id: 1 byte representing the version id.
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//
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// For version_id = 0:
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//
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// version_format: <field><field>
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// field_format: <field_id><field_format>
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//
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// Fields:
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//
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// TraceId: (field_id = 0, len = 16, default = "0000000000000000") - 16-byte array representing the trace_id.
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// SpanId: (field_id = 1, len = 8, default = "00000000") - 8-byte array representing the span_id.
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// TraceOptions: (field_id = 2, len = 1, default = "0") - 1-byte array representing the trace_options.
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//
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// Fields MUST be encoded using the field id order (smaller to higher).
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//
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// Valid value example:
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//
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// {0, 0, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 1, 97,
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// 98, 99, 100, 101, 102, 103, 104, 2, 1}
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//
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// version_id = 0;
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// trace_id = {64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79}
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// span_id = {97, 98, 99, 100, 101, 102, 103, 104};
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// trace_options = {1};
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import (
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"net/http"
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"go.opencensus.io/trace"
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)
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// Binary returns the binary format representation of a SpanContext.
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//
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// If sc is the zero value, Binary returns nil.
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func Binary(sc trace.SpanContext) []byte {
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if sc == (trace.SpanContext{}) {
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return nil
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}
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var b [29]byte
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copy(b[2:18], sc.TraceID[:])
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b[18] = 1
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copy(b[19:27], sc.SpanID[:])
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b[27] = 2
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b[28] = uint8(sc.TraceOptions)
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return b[:]
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}
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// FromBinary returns the SpanContext represented by b.
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//
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// If b has an unsupported version ID or contains no TraceID, FromBinary
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// returns with ok==false.
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func FromBinary(b []byte) (sc trace.SpanContext, ok bool) {
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if len(b) == 0 || b[0] != 0 {
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return trace.SpanContext{}, false
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}
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b = b[1:]
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if len(b) >= 17 && b[0] == 0 {
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copy(sc.TraceID[:], b[1:17])
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b = b[17:]
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} else {
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return trace.SpanContext{}, false
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}
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if len(b) >= 9 && b[0] == 1 {
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copy(sc.SpanID[:], b[1:9])
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b = b[9:]
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}
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if len(b) >= 2 && b[0] == 2 {
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sc.TraceOptions = trace.TraceOptions(b[1])
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}
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return sc, true
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}
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// HTTPFormat implementations propagate span contexts
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// in HTTP requests.
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//
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// SpanContextFromRequest extracts a span context from incoming
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// requests.
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//
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// SpanContextToRequest modifies the given request to include the given
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// span context.
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type HTTPFormat interface {
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SpanContextFromRequest(req *http.Request) (sc trace.SpanContext, ok bool)
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SpanContextToRequest(sc trace.SpanContext, req *http.Request)
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}
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// TODO(jbd): Find a more representative but short name for HTTPFormat.
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