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package opentracing
import "github.com/opentracing/opentracing-go/log"
// A NoopTracer is a trivial, minimum overhead implementation of Tracer
// for which all operations are no-ops.
//
// The primary use of this implementation is in libraries, such as RPC
// frameworks, that make tracing an optional feature controlled by the
// end user. A no-op implementation allows said libraries to use it
// as the default Tracer and to write instrumentation that does
// not need to keep checking if the tracer instance is nil.
//
// For the same reason, the NoopTracer is the default "global" tracer
// (see GlobalTracer and SetGlobalTracer functions).
//
// WARNING: NoopTracer does not support baggage propagation.
type NoopTracer struct{}
type noopSpan struct{}
type noopSpanContext struct{}
var (
defaultNoopSpanContext = noopSpanContext{}
defaultNoopSpan = noopSpan{}
defaultNoopTracer = NoopTracer{}
)
const (
emptyString = ""
)
// noopSpanContext:
func (n noopSpanContext) ForeachBaggageItem(handler func(k, v string) bool) {}
// noopSpan:
func (n noopSpan) Context() SpanContext { return defaultNoopSpanContext }
func (n noopSpan) SetBaggageItem(key, val string) Span { return defaultNoopSpan }
func (n noopSpan) BaggageItem(key string) string { return emptyString }
func (n noopSpan) SetTag(key string, value interface{}) Span { return n }
func (n noopSpan) LogFields(fields ...log.Field) {}
func (n noopSpan) LogKV(keyVals ...interface{}) {}
func (n noopSpan) Finish() {}
func (n noopSpan) FinishWithOptions(opts FinishOptions) {}
func (n noopSpan) SetOperationName(operationName string) Span { return n }
func (n noopSpan) Tracer() Tracer { return defaultNoopTracer }
func (n noopSpan) LogEvent(event string) {}
func (n noopSpan) LogEventWithPayload(event string, payload interface{}) {}
func (n noopSpan) Log(data LogData) {}
// StartSpan belongs to the Tracer interface.
func (n NoopTracer) StartSpan(operationName string, opts ...StartSpanOption) Span {
return defaultNoopSpan
}
// Inject belongs to the Tracer interface.
func (n NoopTracer) Inject(sp SpanContext, format interface{}, carrier interface{}) error {
return nil
}
// Extract belongs to the Tracer interface.
func (n NoopTracer) Extract(format interface{}, carrier interface{}) (SpanContext, error) {
return nil, ErrSpanContextNotFound
}