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147 lines
4.2 KiB
147 lines
4.2 KiB
// Copyright The OpenTelemetry 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 global
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/*
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This file contains the forwarding implementation of the TracerProvider used as
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the default global instance. Prior to initialization of an SDK, Tracers
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returned by the global TracerProvider will provide no-op functionality. This
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means that all Span created prior to initialization are no-op Spans.
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Once an SDK has been initialized, all provided no-op Tracers are swapped for
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Tracers provided by the SDK defined TracerProvider. However, any Span started
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prior to this initialization does not change its behavior. Meaning, the Span
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remains a no-op Span.
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The implementation to track and swap Tracers locks all new Tracer creation
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until the swap is complete. This assumes that this operation is not
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performance-critical. If that assumption is incorrect, be sure to configure an
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SDK prior to any Tracer creation.
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*/
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import (
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"context"
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"sync"
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"sync/atomic"
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"go.opentelemetry.io/otel/internal/trace/noop"
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"go.opentelemetry.io/otel/trace"
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)
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// tracerProvider is a placeholder for a configured SDK TracerProvider.
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//
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// All TracerProvider functionality is forwarded to a delegate once
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// configured.
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type tracerProvider struct {
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mtx sync.Mutex
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tracers map[il]*tracer
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delegate trace.TracerProvider
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}
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// Compile-time guarantee that tracerProvider implements the TracerProvider
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// interface.
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var _ trace.TracerProvider = &tracerProvider{}
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// setDelegate configures p to delegate all TracerProvider functionality to
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// provider.
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//
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// All Tracers provided prior to this function call are switched out to be
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// Tracers provided by provider.
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//
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// It is guaranteed by the caller that this happens only once.
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func (p *tracerProvider) setDelegate(provider trace.TracerProvider) {
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p.mtx.Lock()
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defer p.mtx.Unlock()
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p.delegate = provider
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if len(p.tracers) == 0 {
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return
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}
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for _, t := range p.tracers {
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t.setDelegate(provider)
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}
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p.tracers = nil
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}
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// Tracer implements TracerProvider.
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func (p *tracerProvider) Tracer(name string, opts ...trace.TracerOption) trace.Tracer {
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p.mtx.Lock()
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defer p.mtx.Unlock()
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if p.delegate != nil {
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return p.delegate.Tracer(name, opts...)
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}
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// At this moment it is guaranteed that no sdk is installed, save the tracer in the tracers map.
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key := il{
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name: name,
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version: trace.NewTracerConfig(opts...).InstrumentationVersion,
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}
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if p.tracers == nil {
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p.tracers = make(map[il]*tracer)
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}
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if val, ok := p.tracers[key]; ok {
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return val
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}
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t := &tracer{name: name, opts: opts}
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p.tracers[key] = t
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return t
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}
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type il struct {
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name string
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version string
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}
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// tracer is a placeholder for a trace.Tracer.
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//
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// All Tracer functionality is forwarded to a delegate once configured.
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// Otherwise, all functionality is forwarded to a NoopTracer.
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type tracer struct {
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name string
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opts []trace.TracerOption
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delegate atomic.Value
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}
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// Compile-time guarantee that tracer implements the trace.Tracer interface.
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var _ trace.Tracer = &tracer{}
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// setDelegate configures t to delegate all Tracer functionality to Tracers
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// created by provider.
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//
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// All subsequent calls to the Tracer methods will be passed to the delegate.
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//
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// It is guaranteed by the caller that this happens only once.
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func (t *tracer) setDelegate(provider trace.TracerProvider) {
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t.delegate.Store(provider.Tracer(t.name, t.opts...))
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}
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// Start implements trace.Tracer by forwarding the call to t.delegate if
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// set, otherwise it forwards the call to a NoopTracer.
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func (t *tracer) Start(ctx context.Context, name string, opts ...trace.SpanOption) (context.Context, trace.Span) {
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delegate := t.delegate.Load()
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if delegate != nil {
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return delegate.(trace.Tracer).Start(ctx, name, opts...)
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}
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return noop.Tracer.Start(ctx, name, opts...)
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}
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