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// 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"
"net/http"
)
// TextMapCarrier is the storage medium used by a TextMapPropagator.
type TextMapCarrier interface {
// DO NOT CHANGE: any modification will not be backwards compatible and
// must never be done outside of a new major release.
// Get returns the value associated with the passed key.
Get(key string) string
// DO NOT CHANGE: any modification will not be backwards compatible and
// must never be done outside of a new major release.
// Set stores the key-value pair.
Set(key string, value string)
// DO NOT CHANGE: any modification will not be backwards compatible and
// must never be done outside of a new major release.
// Keys lists the keys stored in this carrier.
Keys() []string
// DO NOT CHANGE: any modification will not be backwards compatible and
// must never be done outside of a new major release.
}
// MapCarrier is a TextMapCarrier that uses a map held in memory as a storage
// medium for propagated key-value pairs.
type MapCarrier map[string]string
// Compile time check that MapCarrier implements the TextMapCarrier.
var _ TextMapCarrier = MapCarrier{}
// Get returns the value associated with the passed key.
func (c MapCarrier) Get(key string) string {
return c[key]
}
// Set stores the key-value pair.
func (c MapCarrier) Set(key, value string) {
c[key] = value
}
// Keys lists the keys stored in this carrier.
func (c MapCarrier) Keys() []string {
keys := make([]string, 0, len(c))
for k := range c {
keys = append(keys, k)
}
return keys
}
// HeaderCarrier adapts http.Header to satisfy the TextMapCarrier interface.
type HeaderCarrier http.Header
// Get returns the value associated with the passed key.
func (hc HeaderCarrier) Get(key string) string {
return http.Header(hc).Get(key)
}
// Set stores the key-value pair.
func (hc HeaderCarrier) Set(key string, value string) {
http.Header(hc).Set(key, value)
}
// Keys lists the keys stored in this carrier.
func (hc HeaderCarrier) Keys() []string {
keys := make([]string, 0, len(hc))
for k := range hc {
keys = append(keys, k)
}
return keys
}
// TextMapPropagator propagates cross-cutting concerns as key-value text
// pairs within a carrier that travels in-band across process boundaries.
type TextMapPropagator interface {
// DO NOT CHANGE: any modification will not be backwards compatible and
// must never be done outside of a new major release.
// Inject set cross-cutting concerns from the Context into the carrier.
Inject(ctx context.Context, carrier TextMapCarrier)
// DO NOT CHANGE: any modification will not be backwards compatible and
// must never be done outside of a new major release.
// Extract reads cross-cutting concerns from the carrier into a Context.
Extract(ctx context.Context, carrier TextMapCarrier) context.Context
// DO NOT CHANGE: any modification will not be backwards compatible and
// must never be done outside of a new major release.
// Fields returns the keys whose values are set with Inject.
Fields() []string
// DO NOT CHANGE: any modification will not be backwards compatible and
// must never be done outside of a new major release.
}
type compositeTextMapPropagator []TextMapPropagator
func (p compositeTextMapPropagator) Inject(ctx context.Context, carrier TextMapCarrier) {
for _, i := range p {
i.Inject(ctx, carrier)
}
}
func (p compositeTextMapPropagator) Extract(ctx context.Context, carrier TextMapCarrier) context.Context {
for _, i := range p {
ctx = i.Extract(ctx, carrier)
}
return ctx
}
func (p compositeTextMapPropagator) Fields() []string {
unique := make(map[string]struct{})
for _, i := range p {
for _, k := range i.Fields() {
unique[k] = struct{}{}
}
}
fields := make([]string, 0, len(unique))
for k := range unique {
fields = append(fields, k)
}
return fields
}
// NewCompositeTextMapPropagator returns a unified TextMapPropagator from the
// group of passed TextMapPropagator. This allows different cross-cutting
// concerns to be propagates in a unified manner.
//
// The returned TextMapPropagator will inject and extract cross-cutting
// concerns in the order the TextMapPropagators were provided. Additionally,
// the Fields method will return a de-duplicated slice of the keys that are
// set with the Inject method.
func NewCompositeTextMapPropagator(p ...TextMapPropagator) TextMapPropagator {
return compositeTextMapPropagator(p)
}
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