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opentelemetry-go/api/global/internal/trace.go
Anthony Mirabella f0c70ffde0
Add StartOptions to Tracer.WithSpan() (#472)
Tracer.WithSpan() will now accept StartOptions as a variadic final parameter `opts`
that will be passed to the Tracer.Start() invocation that creates the Span
wrapping the user-provided function.
2020-02-10 21:07:32 -05:00

119 lines
3.6 KiB
Go

package internal
/*
This file contains the forwarding implementation of the trace.Provider used as
the default global instance. Prior to initialization of an SDK, Tracers
returned by the global Provider 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 Provider. 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"
"go.opentelemetry.io/otel/api/trace"
)
// traceProvider is a placeholder for a configured SDK Provider.
//
// All Provider functionality is forwarded to a delegate once configured.
type traceProvider struct {
mtx sync.Mutex
tracers []*tracer
delegate trace.Provider
}
// Compile-time guarantee that traceProvider implements the trace.Provider interface.
var _ trace.Provider = &traceProvider{}
// setDelegate configures p to delegate all Provider functionality to provider.
//
// All Tracers provided prior to this function call are switched out to be
// Tracers provided by provider.
//
// Delegation only happens on the first call to this method. All subsequent
// calls result in no delegation changes.
func (p *traceProvider) setDelegate(provider trace.Provider) {
if p.delegate != nil {
return
}
p.mtx.Lock()
defer p.mtx.Unlock()
p.delegate = provider
for _, t := range p.tracers {
t.setDelegate(provider)
}
p.tracers = nil
}
// Tracer implements trace.Provider.
func (p *traceProvider) Tracer(name string) trace.Tracer {
p.mtx.Lock()
defer p.mtx.Unlock()
if p.delegate != nil {
return p.delegate.Tracer(name)
}
t := &tracer{name: name}
p.tracers = append(p.tracers, t)
return t
}
// 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 {
once sync.Once
name string
delegate trace.Tracer
}
// 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.
//
// Delegation only happens on the first call to this method. All subsequent
// calls result in no delegation changes.
func (t *tracer) setDelegate(provider trace.Provider) {
t.once.Do(func() { t.delegate = provider.Tracer(t.name) })
}
// WithSpan implements trace.Tracer by forwarding the call to t.delegate if
// set, otherwise it forwards the call to a NoopTracer.
func (t *tracer) WithSpan(ctx context.Context, name string, body func(context.Context) error, opts ...trace.StartOption) error {
if t.delegate != nil {
return t.delegate.WithSpan(ctx, name, body, opts...)
}
return trace.NoopTracer{}.WithSpan(ctx, name, body, 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.StartOption) (context.Context, trace.Span) {
if t.delegate != nil {
return t.delegate.Start(ctx, name, opts...)
}
return trace.NoopTracer{}.Start(ctx, name, opts...)
}