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 propagation // import "go.opentelemetry.io/otel/propagation" 16 17 import ( 18 "context" 19 20 "go.opentelemetry.io/otel/baggage" 21 ) 22 23 const baggageHeader = "baggage" 24 25 // Baggage is a propagator that supports the W3C Baggage format. 26 // 27 // This propagates user-defined baggage associated with a trace. The complete 28 // specification is defined at https://www.w3.org/TR/baggage/. 29 type Baggage struct{} 30 31 var _ TextMapPropagator = Baggage{} 32 33 // Inject sets baggage key-values from ctx into the carrier. 34 func (b Baggage) Inject(ctx context.Context, carrier TextMapCarrier) { 35 bStr := baggage.FromContext(ctx).String() 36 if bStr != "" { 37 carrier.Set(baggageHeader, bStr) 38 } 39 } 40 41 // Extract returns a copy of parent with the baggage from the carrier added. 42 func (b Baggage) Extract(parent context.Context, carrier TextMapCarrier) context.Context { 43 bStr := carrier.Get(baggageHeader) 44 if bStr == "" { 45 return parent 46 } 47 48 bag, err := baggage.Parse(bStr) 49 if err != nil { 50 return parent 51 } 52 return baggage.ContextWithBaggage(parent, bag) 53 } 54 55 // Fields returns the keys who's values are set with Inject. 56 func (b Baggage) Fields() []string { 57 return []string{baggageHeader} 58 } 59