ceph-csi/vendor/go.opentelemetry.io/otel/internal/global/trace.go

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