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 SpanContext = noopSpanContext{} defaultNoopSpan Span = noopSpan{} defaultNoopTracer Tracer = 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 n } 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 }