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// Copyright 2022 The OpenZipkin 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 zipkin
import (
"context"
"github.com/openzipkin/zipkin-go/model"
)
var defaultNoopSpan = &noopSpan{}
// SpanFromContext retrieves a Zipkin Span from Go's context propagation
// mechanism if found. If not found, returns nil.
func SpanFromContext(ctx context.Context) Span {
if s, ok := ctx.Value(spanKey).(Span); ok {
return s
}
return nil
}
// SpanOrNoopFromContext retrieves a Zipkin Span from Go's context propagation
// mechanism if found. If not found, returns a noopSpan.
// This function typically is used for modules that want to provide existing
// Zipkin spans with additional data, but can't guarantee that spans are
// properly propagated. It is preferred to use SpanFromContext() and test for
// Nil instead of using this function.
func SpanOrNoopFromContext(ctx context.Context) Span {
if s, ok := ctx.Value(spanKey).(Span); ok {
return s
}
return defaultNoopSpan
}
// NewContext stores a Zipkin Span into Go's context propagation mechanism.
func NewContext(ctx context.Context, s Span) context.Context {
return context.WithValue(ctx, spanKey, s)
}
// BaggageFromContext takes a context and returns access to BaggageFields if
// available. Returns nil if there are no BaggageFields found in context.
func BaggageFromContext(ctx context.Context) model.BaggageFields {
if span := SpanFromContext(ctx); span != nil {
return span.Context().Baggage
}
return nil
}
type ctxKey struct{}
var spanKey = ctxKey{}
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