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propagation.go
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propagation.go
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// Copyright (c) 2016 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package jaeger
import (
"bytes"
"encoding/binary"
"fmt"
"io"
"log"
"net/url"
"strings"
"sync"
opentracing "github.com/opentracing/opentracing-go"
)
// Injector is responsible for injecting SpanContext instances in a manner suitable
// for propagation via a format-specific "carrier" object. Typically the
// injection will take place across an RPC boundary, but message queues and
// other IPC mechanisms are also reasonable places to use an Injector.
type Injector interface {
// Inject takes `SpanContext` and injects it into `carrier`. The actual type
// of `carrier` depends on the `format` passed to `Tracer.Inject()`.
//
// Implementations may return opentracing.ErrInvalidCarrier or any other
// implementation-specific error if injection fails.
Inject(ctx SpanContext, carrier interface{}) error
}
// Extractor is responsible for extracting SpanContext instances from a
// format-specific "carrier" object. Typically the extraction will take place
// on the server side of an RPC boundary, but message queues and other IPC
// mechanisms are also reasonable places to use an Extractor.
type Extractor interface {
// Extract decodes a SpanContext instance from the given `carrier`,
// or (nil, opentracing.ErrSpanContextNotFound) if no context could
// be found in the `carrier`.
Extract(carrier interface{}) (SpanContext, error)
}
type textMapPropagator struct {
tracer *tracer
encodeValue func(string) string
decodeValue func(string) string
}
func newTextMapPropagator(tracer *tracer) *textMapPropagator {
return &textMapPropagator{
tracer: tracer,
encodeValue: func(val string) string {
return val
},
decodeValue: func(val string) string {
return val
},
}
}
func newHTTPHeaderPropagator(tracer *tracer) *textMapPropagator {
return &textMapPropagator{
tracer: tracer,
encodeValue: func(val string) string {
return url.QueryEscape(val)
},
decodeValue: func(val string) string {
// ignore decoding errors, cannot do anything about them
if v, err := url.QueryUnescape(val); err == nil {
return v
}
return val
},
}
}
type binaryPropagator struct {
tracer *tracer
buffers sync.Pool
}
func newBinaryPropagator(tracer *tracer) *binaryPropagator {
return &binaryPropagator{
tracer: tracer,
buffers: sync.Pool{New: func() interface{} { return &bytes.Buffer{} }},
}
}
func (p *textMapPropagator) Inject(
sc SpanContext,
abstractCarrier interface{},
) error {
textMapWriter, ok := abstractCarrier.(opentracing.TextMapWriter)
if !ok {
return opentracing.ErrInvalidCarrier
}
// Do not encode the string with trace context to avoid accidental double-encoding
// if people are using opentracing < 0.10.0. Our colon-separated representation
// of the trace context is already safe for HTTP headers.
textMapWriter.Set(TracerStateHeaderName, sc.String())
for k, v := range sc.baggage {
safeKey := addBaggageKeyPrefix(k)
safeVal := p.encodeValue(v)
textMapWriter.Set(safeKey, safeVal)
}
return nil
}
func (p *textMapPropagator) Extract(abstractCarrier interface{}) (SpanContext, error) {
textMapReader, ok := abstractCarrier.(opentracing.TextMapReader)
if !ok {
return emptyContext, opentracing.ErrInvalidCarrier
}
var ctx SpanContext
var baggage map[string]string
err := textMapReader.ForeachKey(func(rawKey, value string) error {
key := strings.ToLower(rawKey) // TODO not necessary for plain TextMap
if key == TracerStateHeaderName {
var err error
safeVal := p.decodeValue(value)
if ctx, err = ContextFromString(safeVal); err != nil {
return err
}
} else if key == JaegerDebugHeader {
ctx.debugID = p.decodeValue(value)
} else if key == JaegerBaggageHeader {
if baggage == nil {
baggage = make(map[string]string)
}
for k, v := range parseCommaSeparatedMap(value) {
baggage[k] = v
}
} else if strings.HasPrefix(key, TraceBaggageHeaderPrefix) {
if baggage == nil {
baggage = make(map[string]string)
}
safeKey := removeBaggageKeyPrefix(key)
safeVal := p.decodeValue(value)
baggage[safeKey] = safeVal
}
return nil
})
if err != nil {
p.tracer.metrics.DecodingErrors.Inc(1)
return emptyContext, err
}
if !ctx.traceID.IsValid() && ctx.debugID == "" && len(baggage) == 0 {
return emptyContext, opentracing.ErrSpanContextNotFound
}
ctx.baggage = baggage
return ctx, nil
}
func (p *binaryPropagator) Inject(
sc SpanContext,
abstractCarrier interface{},
) error {
carrier, ok := abstractCarrier.(io.Writer)
if !ok {
return opentracing.ErrInvalidCarrier
}
// Handle the tracer context
if err := binary.Write(carrier, binary.BigEndian, sc.traceID); err != nil {
return err
}
if err := binary.Write(carrier, binary.BigEndian, sc.spanID); err != nil {
return err
}
if err := binary.Write(carrier, binary.BigEndian, sc.parentID); err != nil {
return err
}
if err := binary.Write(carrier, binary.BigEndian, sc.flags); err != nil {
return err
}
// Handle the baggage items
if err := binary.Write(carrier, binary.BigEndian, int32(len(sc.baggage))); err != nil {
return err
}
for k, v := range sc.baggage {
if err := binary.Write(carrier, binary.BigEndian, int32(len(k))); err != nil {
return err
}
io.WriteString(carrier, k)
if err := binary.Write(carrier, binary.BigEndian, int32(len(v))); err != nil {
return err
}
io.WriteString(carrier, v)
}
return nil
}
func (p *binaryPropagator) Extract(abstractCarrier interface{}) (SpanContext, error) {
carrier, ok := abstractCarrier.(io.Reader)
if !ok {
return emptyContext, opentracing.ErrInvalidCarrier
}
var ctx SpanContext
if err := binary.Read(carrier, binary.BigEndian, &ctx.traceID); err != nil {
return emptyContext, opentracing.ErrSpanContextCorrupted
}
if err := binary.Read(carrier, binary.BigEndian, &ctx.spanID); err != nil {
return emptyContext, opentracing.ErrSpanContextCorrupted
}
if err := binary.Read(carrier, binary.BigEndian, &ctx.parentID); err != nil {
return emptyContext, opentracing.ErrSpanContextCorrupted
}
if err := binary.Read(carrier, binary.BigEndian, &ctx.flags); err != nil {
return emptyContext, opentracing.ErrSpanContextCorrupted
}
// Handle the baggage items
var numBaggage int32
if err := binary.Read(carrier, binary.BigEndian, &numBaggage); err != nil {
return emptyContext, opentracing.ErrSpanContextCorrupted
}
if iNumBaggage := int(numBaggage); iNumBaggage > 0 {
ctx.baggage = make(map[string]string, iNumBaggage)
buf := p.buffers.Get().(*bytes.Buffer)
defer p.buffers.Put(buf)
var keyLen, valLen int32
for i := 0; i < iNumBaggage; i++ {
if err := binary.Read(carrier, binary.BigEndian, &keyLen); err != nil {
return emptyContext, opentracing.ErrSpanContextCorrupted
}
buf.Reset()
buf.Grow(int(keyLen))
if n, err := io.CopyN(buf, carrier, int64(keyLen)); err != nil || int32(n) != keyLen {
return emptyContext, opentracing.ErrSpanContextCorrupted
}
key := buf.String()
if err := binary.Read(carrier, binary.BigEndian, &valLen); err != nil {
return emptyContext, opentracing.ErrSpanContextCorrupted
}
buf.Reset()
buf.Grow(int(valLen))
if n, err := io.CopyN(buf, carrier, int64(valLen)); err != nil || int32(n) != valLen {
return emptyContext, opentracing.ErrSpanContextCorrupted
}
ctx.baggage[key] = buf.String()
}
}
return ctx, nil
}
// Converts a comma separated key value pair list into a map
// e.g. key1=value1, key2=value2, key3 = value3
// is converted to map[string]string { "key1" : "value1",
// "key2" : "value2",
// "key3" : "value3" }
func parseCommaSeparatedMap(value string) map[string]string {
baggage := make(map[string]string)
value, err := url.QueryUnescape(value)
if err != nil {
log.Printf("Unable to unescape %s, %v", value, err)
return baggage
}
for _, kvpair := range strings.Split(value, ",") {
kv := strings.Split(strings.TrimSpace(kvpair), "=")
if len(kv) == 2 {
baggage[kv[0]] = kv[1]
} else {
log.Printf("Malformed value passed in for %s", JaegerBaggageHeader)
}
}
return baggage
}
// Converts a baggage item key into an http header format,
// by prepending TraceBaggageHeaderPrefix and encoding the key string
func addBaggageKeyPrefix(key string) string {
// TODO encodeBaggageKeyAsHeader add caching and escaping
return fmt.Sprintf("%v%v", TraceBaggageHeaderPrefix, key)
}
func removeBaggageKeyPrefix(key string) string {
// TODO decodeBaggageHeaderKey add caching and escaping
return key[len(TraceBaggageHeaderPrefix):]
}