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82 lines
2.6 KiB
82 lines
2.6 KiB
// Copyright The OpenTelemetry Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package global
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import (
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"context"
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"sync"
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"go.opentelemetry.io/otel/propagation"
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)
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// textMapPropagator is a default TextMapPropagator that delegates calls to a
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// registered delegate if one is set, otherwise it defaults to delegating the
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// calls to a the default no-op propagation.TextMapPropagator.
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type textMapPropagator struct {
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mtx sync.Mutex
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once sync.Once
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delegate propagation.TextMapPropagator
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noop propagation.TextMapPropagator
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}
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// Compile-time guarantee that textMapPropagator implements the
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// propagation.TextMapPropagator interface.
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var _ propagation.TextMapPropagator = (*textMapPropagator)(nil)
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func newTextMapPropagator() *textMapPropagator {
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return &textMapPropagator{
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noop: propagation.NewCompositeTextMapPropagator(),
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}
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}
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// SetDelegate sets a delegate propagation.TextMapPropagator that all calls are
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// forwarded to. Delegation can only be performed once, all subsequent calls
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// perform no delegation.
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func (p *textMapPropagator) SetDelegate(delegate propagation.TextMapPropagator) {
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if delegate == nil {
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return
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}
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p.mtx.Lock()
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p.once.Do(func() { p.delegate = delegate })
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p.mtx.Unlock()
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}
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// effectiveDelegate returns the current delegate of p if one is set,
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// otherwise the default noop TextMapPropagator is returned. This method
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// can be called concurrently.
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func (p *textMapPropagator) effectiveDelegate() propagation.TextMapPropagator {
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p.mtx.Lock()
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defer p.mtx.Unlock()
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if p.delegate != nil {
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return p.delegate
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}
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return p.noop
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}
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// Inject set cross-cutting concerns from the Context into the carrier.
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func (p *textMapPropagator) Inject(ctx context.Context, carrier propagation.TextMapCarrier) {
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p.effectiveDelegate().Inject(ctx, carrier)
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}
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// Extract reads cross-cutting concerns from the carrier into a Context.
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func (p *textMapPropagator) Extract(ctx context.Context, carrier propagation.TextMapCarrier) context.Context {
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return p.effectiveDelegate().Extract(ctx, carrier)
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}
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// Fields returns the keys whose values are set with Inject.
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func (p *textMapPropagator) Fields() []string {
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return p.effectiveDelegate().Fields()
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}
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