noop.go

Documentation: github.com/opentracing/opentracing-go

     1  package opentracing
     2  
     3  import "github.com/opentracing/opentracing-go/log"
     4  
     5  // A NoopTracer is a trivial, minimum overhead implementation of Tracer
     6  // for which all operations are no-ops.
     7  //
     8  // The primary use of this implementation is in libraries, such as RPC
     9  // frameworks, that make tracing an optional feature controlled by the
    10  // end user. A no-op implementation allows said libraries to use it
    11  // as the default Tracer and to write instrumentation that does
    12  // not need to keep checking if the tracer instance is nil.
    13  //
    14  // For the same reason, the NoopTracer is the default "global" tracer
    15  // (see GlobalTracer and SetGlobalTracer functions).
    16  //
    17  // WARNING: NoopTracer does not support baggage propagation.
    18  type NoopTracer struct{}
    19  
    20  type noopSpan struct{}
    21  type noopSpanContext struct{}
    22  
    23  var (
    24  	defaultNoopSpanContext SpanContext = noopSpanContext{}
    25  	defaultNoopSpan        Span        = noopSpan{}
    26  	defaultNoopTracer      Tracer      = NoopTracer{}
    27  )
    28  
    29  const (
    30  	emptyString = ""
    31  )
    32  
    33  // noopSpanContext:
    34  func (n noopSpanContext) ForeachBaggageItem(handler func(k, v string) bool) {}
    35  
    36  // noopSpan:
    37  func (n noopSpan) Context() SpanContext                                  { return defaultNoopSpanContext }
    38  func (n noopSpan) SetBaggageItem(key, val string) Span                   { return n }
    39  func (n noopSpan) BaggageItem(key string) string                         { return emptyString }
    40  func (n noopSpan) SetTag(key string, value interface{}) Span             { return n }
    41  func (n noopSpan) LogFields(fields ...log.Field)                         {}
    42  func (n noopSpan) LogKV(keyVals ...interface{})                          {}
    43  func (n noopSpan) Finish()                                               {}
    44  func (n noopSpan) FinishWithOptions(opts FinishOptions)                  {}
    45  func (n noopSpan) SetOperationName(operationName string) Span            { return n }
    46  func (n noopSpan) Tracer() Tracer                                        { return defaultNoopTracer }
    47  func (n noopSpan) LogEvent(event string)                                 {}
    48  func (n noopSpan) LogEventWithPayload(event string, payload interface{}) {}
    49  func (n noopSpan) Log(data LogData)                                      {}
    50  
    51  // StartSpan belongs to the Tracer interface.
    52  func (n NoopTracer) StartSpan(operationName string, opts ...StartSpanOption) Span {
    53  	return defaultNoopSpan
    54  }
    55  
    56  // Inject belongs to the Tracer interface.
    57  func (n NoopTracer) Inject(sp SpanContext, format interface{}, carrier interface{}) error {
    58  	return nil
    59  }
    60  
    61  // Extract belongs to the Tracer interface.
    62  func (n NoopTracer) Extract(format interface{}, carrier interface{}) (SpanContext, error) {
    63  	return nil, ErrSpanContextNotFound
    64  }
    65
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