traefik/vendor/github.com/ExpediaDotCom/haystack-client-go/propagator.go

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2019-05-08 22:14:04 +00:00
/*
* Copyright 2018 Expedia Group.
*
* 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 haystack
import (
"fmt"
"net/url"
"strings"
"github.com/opentracing/opentracing-go"
)
/*Propagator defines the interface for injecting and extracing the SpanContext from the carrier*/
type Propagator interface {
// Inject takes `SpanContext` and injects it into `carrier`
Inject(ctx *SpanContext, carrier interface{}) error
// Extract `SpanContext` from the `carrier`
Extract(carrier interface{}) (*SpanContext, error)
}
/*Codex defines the interface for encoding and decoding the propagated data*/
type Codex interface {
Encode(value string) string
Decode(value string) string
}
/*DefaultCodex is a no op*/
type DefaultCodex struct{}
/*Encode a no-op for encoding the value*/
func (c DefaultCodex) Encode(value string) string { return value }
/*Decode a no-op for decoding the value*/
func (c DefaultCodex) Decode(value string) string { return value }
/*URLCodex encodes decodes a url*/
type URLCodex struct{}
/*Encode a no-op for encoding the value*/
func (c URLCodex) Encode(value string) string { return url.QueryEscape(value) }
/*Decode a no-op for decoding the value*/
func (c URLCodex) Decode(value string) string {
decoded, err := url.QueryUnescape(value)
if err == nil {
return decoded
}
return ""
}
/*PropagatorOpts defines the options need by a propagator*/
type PropagatorOpts struct {
TraceIDKEYName string
SpanIDKEYName string
ParentSpanIDKEYName string
BaggagePrefixKEYName string
}
var defaultPropagatorOpts = PropagatorOpts{}
var defaultCodex = DefaultCodex{}
/*TraceIDKEY returns the trace id key in the propagator*/
func (p *PropagatorOpts) TraceIDKEY() string {
if p.TraceIDKEYName != "" {
return p.TraceIDKEYName
}
return "Trace-ID"
}
/*SpanIDKEY returns the span id key in the propagator*/
func (p *PropagatorOpts) SpanIDKEY() string {
if p.SpanIDKEYName != "" {
return p.SpanIDKEYName
}
return "Span-ID"
}
/*ParentSpanIDKEY returns the parent span id key in the propagator*/
func (p *PropagatorOpts) ParentSpanIDKEY() string {
if p.ParentSpanIDKEYName != "" {
return p.ParentSpanIDKEYName
}
return "Parent-ID"
}
/*BaggageKeyPrefix returns the baggage key prefix*/
func (p *PropagatorOpts) BaggageKeyPrefix() string {
if p.BaggagePrefixKEYName != "" {
return p.BaggagePrefixKEYName
}
return "Baggage-"
}
/*TextMapPropagator implements Propagator interface*/
type TextMapPropagator struct {
opts PropagatorOpts
codex Codex
}
/*Inject injects the span context in the carrier*/
func (p *TextMapPropagator) Inject(ctx *SpanContext, carrier interface{}) error {
textMapWriter, ok := carrier.(opentracing.TextMapWriter)
if !ok {
return opentracing.ErrInvalidCarrier
}
textMapWriter.Set(p.opts.TraceIDKEY(), ctx.TraceID)
textMapWriter.Set(p.opts.SpanIDKEY(), ctx.SpanID)
textMapWriter.Set(p.opts.ParentSpanIDKEY(), ctx.ParentID)
ctx.ForeachBaggageItem(func(key, value string) bool {
textMapWriter.Set(fmt.Sprintf("%s%s", p.opts.BaggageKeyPrefix(), key), p.codex.Encode(ctx.Baggage[key]))
return true
})
return nil
}
/*Extract the span context from the carrier*/
func (p *TextMapPropagator) Extract(carrier interface{}) (*SpanContext, error) {
textMapReader, ok := carrier.(opentracing.TextMapReader)
if !ok {
return nil, opentracing.ErrInvalidCarrier
}
baggageKeyLowerCasePrefix := strings.ToLower(p.opts.BaggageKeyPrefix())
traceIDKeyLowerCase := strings.ToLower(p.opts.TraceIDKEY())
spanIDKeyLowerCase := strings.ToLower(p.opts.SpanIDKEY())
parentSpanIDKeyLowerCase := strings.ToLower(p.opts.ParentSpanIDKEY())
traceID := ""
spanID := ""
parentSpanID := ""
baggage := make(map[string]string)
err := textMapReader.ForeachKey(func(k, v string) error {
lcKey := strings.ToLower(k)
if strings.HasPrefix(lcKey, baggageKeyLowerCasePrefix) {
keySansPrefix := lcKey[len(p.opts.BaggageKeyPrefix()):]
baggage[keySansPrefix] = p.codex.Decode(v)
} else if lcKey == traceIDKeyLowerCase {
traceID = v
} else if lcKey == spanIDKeyLowerCase {
spanID = v
} else if lcKey == parentSpanIDKeyLowerCase {
parentSpanID = v
}
return nil
})
if err != nil {
return nil, err
}
return &SpanContext{
TraceID: traceID,
SpanID: spanID,
ParentID: parentSpanID,
Baggage: baggage,
IsExtractedContext: true,
}, nil
}
/*NewDefaultTextMapPropagator returns a default text map propagator*/
func NewDefaultTextMapPropagator() *TextMapPropagator {
return NewTextMapPropagator(defaultPropagatorOpts, defaultCodex)
}
/*NewTextMapPropagator returns a text map propagator*/
func NewTextMapPropagator(opts PropagatorOpts, codex Codex) *TextMapPropagator {
return &TextMapPropagator{
opts: opts,
codex: codex,
}
}