gtsocial-umbx

Unnamed repository; edit this file 'description' to name the repository.
Log | Files | Refs | README | LICENSE

propagator.go (2758B)

      1 // Copyright The OpenTelemetry Authors
      2 //
      3 // Licensed under the Apache License, Version 2.0 (the "License");
      4 // you may not use this file except in compliance with the License.
      5 // You may obtain a copy of the License at
      6 //
      7 //     http://www.apache.org/licenses/LICENSE-2.0
      8 //
      9 // Unless required by applicable law or agreed to in writing, software
     10 // distributed under the License is distributed on an "AS IS" BASIS,
     11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     12 // See the License for the specific language governing permissions and
     13 // limitations under the License.
     14 
     15 package global // import "go.opentelemetry.io/otel/internal/global"
     16 
     17 import (
     18 	"context"
     19 	"sync"
     20 
     21 	"go.opentelemetry.io/otel/propagation"
     22 )
     23 
     24 // textMapPropagator is a default TextMapPropagator that delegates calls to a
     25 // registered delegate if one is set, otherwise it defaults to delegating the
     26 // calls to a the default no-op propagation.TextMapPropagator.
     27 type textMapPropagator struct {
     28 	mtx      sync.Mutex
     29 	once     sync.Once
     30 	delegate propagation.TextMapPropagator
     31 	noop     propagation.TextMapPropagator
     32 }
     33 
     34 // Compile-time guarantee that textMapPropagator implements the
     35 // propagation.TextMapPropagator interface.
     36 var _ propagation.TextMapPropagator = (*textMapPropagator)(nil)
     37 
     38 func newTextMapPropagator() *textMapPropagator {
     39 	return &textMapPropagator{
     40 		noop: propagation.NewCompositeTextMapPropagator(),
     41 	}
     42 }
     43 
     44 // SetDelegate sets a delegate propagation.TextMapPropagator that all calls are
     45 // forwarded to. Delegation can only be performed once, all subsequent calls
     46 // perform no delegation.
     47 func (p *textMapPropagator) SetDelegate(delegate propagation.TextMapPropagator) {
     48 	if delegate == nil {
     49 		return
     50 	}
     51 
     52 	p.mtx.Lock()
     53 	p.once.Do(func() { p.delegate = delegate })
     54 	p.mtx.Unlock()
     55 }
     56 
     57 // effectiveDelegate returns the current delegate of p if one is set,
     58 // otherwise the default noop TextMapPropagator is returned. This method
     59 // can be called concurrently.
     60 func (p *textMapPropagator) effectiveDelegate() propagation.TextMapPropagator {
     61 	p.mtx.Lock()
     62 	defer p.mtx.Unlock()
     63 	if p.delegate != nil {
     64 		return p.delegate
     65 	}
     66 	return p.noop
     67 }
     68 
     69 // Inject set cross-cutting concerns from the Context into the carrier.
     70 func (p *textMapPropagator) Inject(ctx context.Context, carrier propagation.TextMapCarrier) {
     71 	p.effectiveDelegate().Inject(ctx, carrier)
     72 }
     73 
     74 // Extract reads cross-cutting concerns from the carrier into a Context.
     75 func (p *textMapPropagator) Extract(ctx context.Context, carrier propagation.TextMapCarrier) context.Context {
     76 	return p.effectiveDelegate().Extract(ctx, carrier)
     77 }
     78 
     79 // Fields returns the keys whose values are set with Inject.
     80 func (p *textMapPropagator) Fields() []string {
     81 	return p.effectiveDelegate().Fields()
     82 }