79 lines
2.7 KiB
Go
79 lines
2.7 KiB
Go
// 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 propagation // import "go.opentelemetry.io/otel/propagation"
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import "context"
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// TextMapCarrier is the storage medium used by a TextMapPropagator.
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type TextMapCarrier interface {
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// Get returns the value associated with the passed key.
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Get(key string) string
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// Set stores the key-value pair.
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Set(key string, value string)
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}
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// TextMapPropagator propagates cross-cutting concerns as key-value text
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// pairs within a carrier that travels in-band across process boundaries.
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type TextMapPropagator interface {
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// Inject set cross-cutting concerns from the Context into the carrier.
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Inject(ctx context.Context, carrier TextMapCarrier)
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// Extract reads cross-cutting concerns from the carrier into a Context.
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Extract(ctx context.Context, carrier TextMapCarrier) context.Context
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// Fields returns the keys who's values are set with Inject.
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Fields() []string
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}
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type compositeTextMapPropagator []TextMapPropagator
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func (p compositeTextMapPropagator) Inject(ctx context.Context, carrier TextMapCarrier) {
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for _, i := range p {
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i.Inject(ctx, carrier)
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}
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}
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func (p compositeTextMapPropagator) Extract(ctx context.Context, carrier TextMapCarrier) context.Context {
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for _, i := range p {
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ctx = i.Extract(ctx, carrier)
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}
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return ctx
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}
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func (p compositeTextMapPropagator) Fields() []string {
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unique := make(map[string]struct{})
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for _, i := range p {
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for _, k := range i.Fields() {
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unique[k] = struct{}{}
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}
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}
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fields := make([]string, 0, len(unique))
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for k := range unique {
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fields = append(fields, k)
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}
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return fields
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}
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// NewCompositeTextMapPropagator returns a unified TextMapPropagator from the
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// group of passed TextMapPropagator. This allows different cross-cutting
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// concerns to be propagates in a unified manner.
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//
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// The returned TextMapPropagator will inject and extract cross-cutting
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// concerns in the order the TextMapPropagators were provided. Additionally,
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// the Fields method will return a de-duplicated slice of the keys that are
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// set with the Inject method.
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func NewCompositeTextMapPropagator(p ...TextMapPropagator) TextMapPropagator {
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return compositeTextMapPropagator(p)
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}
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