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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 trace // import "go.opentelemetry.io/otel/sdk/trace"
import (
"context"
"sync"
"go.opentelemetry.io/otel"
)
// simpleSpanProcessor is a SpanProcessor that synchronously sends all
// completed Spans to a trace.Exporter immediately.
type simpleSpanProcessor struct {
exporterMu sync.RWMutex
exporter SpanExporter
stopOnce sync.Once
}
var _ SpanProcessor = (*simpleSpanProcessor)(nil)
// NewSimpleSpanProcessor returns a new SpanProcessor that will synchronously
// send completed spans to the exporter immediately.
//
// This SpanProcessor is not recommended for production use. The synchronous
// nature of this SpanProcessor make it good for testing, debugging, or
// showing examples of other feature, but it will be slow and have a high
// computation resource usage overhead. The BatchSpanProcessor is recommended
// for production use instead.
func NewSimpleSpanProcessor(exporter SpanExporter) SpanProcessor {
ssp := &simpleSpanProcessor{
exporter: exporter,
}
return ssp
}
// OnStart does nothing.
func (ssp *simpleSpanProcessor) OnStart(context.Context, ReadWriteSpan) {}
// OnEnd immediately exports a ReadOnlySpan.
func (ssp *simpleSpanProcessor) OnEnd(s ReadOnlySpan) {
ssp.exporterMu.RLock()
defer ssp.exporterMu.RUnlock()
if ssp.exporter != nil && s.SpanContext().TraceFlags().IsSampled() {
if err := ssp.exporter.ExportSpans(context.Background(), []ReadOnlySpan{s}); err != nil {
otel.Handle(err)
}
}
}
// Shutdown shuts down the exporter this SimpleSpanProcessor exports to.
func (ssp *simpleSpanProcessor) Shutdown(ctx context.Context) error {
var err error
ssp.stopOnce.Do(func() {
stopFunc := func(exp SpanExporter) (<-chan error, func()) {
done := make(chan error)
return done, func() { done <- exp.Shutdown(ctx) }
}
// The exporter field of the simpleSpanProcessor needs to be zeroed to
// signal it is shut down, meaning all subsequent calls to OnEnd will
// be gracefully ignored. This needs to be done synchronously to avoid
// any race condition.
//
// A closure is used to keep reference to the exporter and then the
// field is zeroed. This ensures the simpleSpanProcessor is shut down
// before the exporter. This order is important as it avoids a
// potential deadlock. If the exporter shut down operation generates a
// span, that span would need to be exported. Meaning, OnEnd would be
// called and try acquiring the lock that is held here.
ssp.exporterMu.Lock()
done, shutdown := stopFunc(ssp.exporter)
ssp.exporter = nil
ssp.exporterMu.Unlock()
go shutdown()
// Wait for the exporter to shut down or the deadline to expire.
select {
case err = <-done:
case <-ctx.Done():
// It is possible for the exporter to have immediately shut down
// and the context to be done simultaneously. In that case this
// outer select statement will randomly choose a case. This will
// result in a different returned error for similar scenarios.
// Instead, double check if the exporter shut down at the same
// time and return that error if so. This will ensure consistency
// as well as ensure the caller knows the exporter shut down
// successfully (they can already determine if the deadline is
// expired given they passed the context).
select {
case err = <-done:
default:
err = ctx.Err()
}
}
})
return err
}
// ForceFlush does nothing as there is no data to flush.
func (ssp *simpleSpanProcessor) ForceFlush(context.Context) error {
return nil
}
// MarshalLog is the marshaling function used by the logging system to represent this Span Processor.
func (ssp *simpleSpanProcessor) MarshalLog() interface{} {
return struct {
Type string
Exporter SpanExporter
}{
Type: "SimpleSpanProcessor",
Exporter: ssp.exporter,
}
}
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