| // 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 global // import "go.opentelemetry.io/otel/internal/global" |
| |
| import ( |
| "context" |
| "sync" |
| |
| "go.opentelemetry.io/otel/propagation" |
| ) |
| |
| // textMapPropagator is a default TextMapPropagator that delegates calls to a |
| // registered delegate if one is set, otherwise it defaults to delegating the |
| // calls to a the default no-op propagation.TextMapPropagator. |
| type textMapPropagator struct { |
| mtx sync.Mutex |
| once sync.Once |
| delegate propagation.TextMapPropagator |
| noop propagation.TextMapPropagator |
| } |
| |
| // Compile-time guarantee that textMapPropagator implements the |
| // propagation.TextMapPropagator interface. |
| var _ propagation.TextMapPropagator = (*textMapPropagator)(nil) |
| |
| func newTextMapPropagator() *textMapPropagator { |
| return &textMapPropagator{ |
| noop: propagation.NewCompositeTextMapPropagator(), |
| } |
| } |
| |
| // SetDelegate sets a delegate propagation.TextMapPropagator that all calls are |
| // forwarded to. Delegation can only be performed once, all subsequent calls |
| // perform no delegation. |
| func (p *textMapPropagator) SetDelegate(delegate propagation.TextMapPropagator) { |
| if delegate == nil { |
| return |
| } |
| |
| p.mtx.Lock() |
| p.once.Do(func() { p.delegate = delegate }) |
| p.mtx.Unlock() |
| } |
| |
| // effectiveDelegate returns the current delegate of p if one is set, |
| // otherwise the default noop TextMapPropagator is returned. This method |
| // can be called concurrently. |
| func (p *textMapPropagator) effectiveDelegate() propagation.TextMapPropagator { |
| p.mtx.Lock() |
| defer p.mtx.Unlock() |
| if p.delegate != nil { |
| return p.delegate |
| } |
| return p.noop |
| } |
| |
| // Inject set cross-cutting concerns from the Context into the carrier. |
| func (p *textMapPropagator) Inject(ctx context.Context, carrier propagation.TextMapCarrier) { |
| p.effectiveDelegate().Inject(ctx, carrier) |
| } |
| |
| // Extract reads cross-cutting concerns from the carrier into a Context. |
| func (p *textMapPropagator) Extract(ctx context.Context, carrier propagation.TextMapCarrier) context.Context { |
| return p.effectiveDelegate().Extract(ctx, carrier) |
| } |
| |
| // Fields returns the keys whose values are set with Inject. |
| func (p *textMapPropagator) Fields() []string { |
| return p.effectiveDelegate().Fields() |
| } |