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72 lines
2.2 KiB
Go
72 lines
2.2 KiB
Go
// Copyright 2017 Pilosa Corp.
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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 tracing
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import (
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"context"
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"net/http"
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)
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// GlobalTracer is a single, global instance of Tracer.
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var GlobalTracer Tracer = NopTracer()
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// StartSpanFromContext returnus a new child span and context from a given
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// context using the global tracer.
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func StartSpanFromContext(ctx context.Context, operationName string) (Span, context.Context) {
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return GlobalTracer.StartSpanFromContext(ctx, operationName)
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}
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// Tracer implements a generic distributed tracing interface.
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type Tracer interface {
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// Returns a new child span and context from a given context.
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StartSpanFromContext(ctx context.Context, operationName string) (Span, context.Context)
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// Adds the required HTTP headers to pass context between nodes.
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InjectHTTPHeaders(r *http.Request)
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// Reads the HTTP headers to derive incoming context.
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ExtractHTTPHeaders(r *http.Request) (Span, context.Context)
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}
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// Span represents a single span in a distributed trace.
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type Span interface {
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// Sets the end timestamp and finalizes Span state.
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Finish()
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// Adds key/value pairs to the span.
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LogKV(alternatingKeyValues ...interface{})
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}
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// NopTracer returns a tracer that doesn't do anything.
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func NopTracer() Tracer {
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return &nopTracer{}
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}
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type nopTracer struct{}
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func (t *nopTracer) StartSpanFromContext(ctx context.Context, operationName string) (Span, context.Context) {
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return &nopSpan{}, ctx
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}
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func (t *nopTracer) InjectHTTPHeaders(r *http.Request) {}
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func (t *nopTracer) ExtractHTTPHeaders(r *http.Request) (Span, context.Context) {
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return &nopSpan{}, r.Context()
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}
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type nopSpan struct{}
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func (s *nopSpan) Finish() {}
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func (s *nopSpan) LogKV(alternatingKeyValues ...interface{}) {}
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