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opentelemetry-go/api/propagators/text_propagator.go
ferhat elmas ab164e6638 Merge propagation and api/propagation into api/propagators (#362)
* Merge propagation

Rename and merge propagation and api/propagation
to api/propagators.

Drop propagator suffix in general such that
TextFormatPropagator becomes TextFormat since
usage is propagators.TextFormat

fixes #311

* Rebase and godoc updates

* Revert go mod changes

* Replace carrier with supplier in godoc
2019-12-03 13:52:03 -08:00

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Go

// Copyright 2019, 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 propagators
import (
"context"
"go.opentelemetry.io/otel/api/core"
dctx "go.opentelemetry.io/otel/api/distributedcontext"
)
// TextFormat is an interface that specifies methods to inject and extract SpanContext
// and distributed context into/from a carrier using Supplier interface.
// For example, HTTP Trace Context propagator would encode SpanContext into W3C Trace
// Context Header and set the header into HttpRequest.
type TextFormat interface {
// Inject method retrieves current SpanContext from the ctx, encodes it into propagator
// specific format and then injects the encoded SpanContext using supplier into a carrier
// associated with the supplier. It also takes a correlationCtx whose values will be
// injected into a carrier using the supplier.
Inject(ctx context.Context, supplier Supplier)
// Extract method retrieves encoded SpanContext using supplier from the associated carrier.
// It decodes the SpanContext and returns it and a dctx of correlated context.
// If no SpanContext was retrieved OR if the retrieved SpanContext is invalid then
// an empty SpanContext is returned.
Extract(ctx context.Context, supplier Supplier) (core.SpanContext, dctx.Map)
// GetAllKeys returns all the keys that this propagator injects/extracts into/from a
// carrier. The use cases for this are
// * allow pre-allocation of fields, especially in systems like gRPC Metadata
// * allow a single-pass over an iterator (ex OpenTracing has no getter in TextMap)
GetAllKeys() []string
}
// Supplier is an interface that specifies methods to retrieve and store
// value for a key to an associated carrier.
// Get method retrieves the value for a given key.
// Set method stores the value for a given key.
type Supplier interface {
Get(key string) string
Set(key string, value string)
}