53 lines
1.7 KiB
Go
53 lines
1.7 KiB
Go
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// Copyright 2019 The OpenZipkin 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 zipkin
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import (
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"context"
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)
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var defaultNoopSpan = &noopSpan{}
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// SpanFromContext retrieves a Zipkin Span from Go's context propagation
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// mechanism if found. If not found, returns nil.
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func SpanFromContext(ctx context.Context) Span {
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if s, ok := ctx.Value(spanKey).(Span); ok {
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return s
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}
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return nil
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}
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// SpanOrNoopFromContext retrieves a Zipkin Span from Go's context propagation
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// mechanism if found. If not found, returns a noopSpan.
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// This function typically is used for modules that want to provide existing
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// Zipkin spans with additional data, but can't guarantee that spans are
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// properly propagated. It is preferred to use SpanFromContext() and test for
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// Nil instead of using this function.
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func SpanOrNoopFromContext(ctx context.Context) Span {
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if s, ok := ctx.Value(spanKey).(Span); ok {
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return s
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}
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return defaultNoopSpan
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}
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// NewContext stores a Zipkin Span into Go's context propagation mechanism.
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func NewContext(ctx context.Context, s Span) context.Context {
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return context.WithValue(ctx, spanKey, s)
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}
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type ctxKey struct{}
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var spanKey = ctxKey{}
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