propagation.go

Documentation: github.com/opentracing/opentracing-go/mocktracer

     1  package mocktracer
     2  
     3  import (
     4  	"fmt"
     5  	"net/url"
     6  	"strconv"
     7  	"strings"
     8  
     9  	"github.com/opentracing/opentracing-go"
    10  )
    11  
    12  const mockTextMapIdsPrefix = "mockpfx-ids-"
    13  const mockTextMapBaggagePrefix = "mockpfx-baggage-"
    14  
    15  var emptyContext = MockSpanContext{}
    16  
    17  // Injector is responsible for injecting SpanContext instances in a manner suitable
    18  // for propagation via a format-specific "carrier" object. Typically the
    19  // injection will take place across an RPC boundary, but message queues and
    20  // other IPC mechanisms are also reasonable places to use an Injector.
    21  type Injector interface {
    22  	// Inject takes `SpanContext` and injects it into `carrier`. The actual type
    23  	// of `carrier` depends on the `format` passed to `Tracer.Inject()`.
    24  	//
    25  	// Implementations may return opentracing.ErrInvalidCarrier or any other
    26  	// implementation-specific error if injection fails.
    27  	Inject(ctx MockSpanContext, carrier interface{}) error
    28  }
    29  
    30  // Extractor is responsible for extracting SpanContext instances from a
    31  // format-specific "carrier" object. Typically the extraction will take place
    32  // on the server side of an RPC boundary, but message queues and other IPC
    33  // mechanisms are also reasonable places to use an Extractor.
    34  type Extractor interface {
    35  	// Extract decodes a SpanContext instance from the given `carrier`,
    36  	// or (nil, opentracing.ErrSpanContextNotFound) if no context could
    37  	// be found in the `carrier`.
    38  	Extract(carrier interface{}) (MockSpanContext, error)
    39  }
    40  
    41  // TextMapPropagator implements Injector/Extractor for TextMap and HTTPHeaders formats.
    42  type TextMapPropagator struct {
    43  	HTTPHeaders bool
    44  }
    45  
    46  // Inject implements the Injector interface
    47  func (t *TextMapPropagator) Inject(spanContext MockSpanContext, carrier interface{}) error {
    48  	writer, ok := carrier.(opentracing.TextMapWriter)
    49  	if !ok {
    50  		return opentracing.ErrInvalidCarrier
    51  	}
    52  	// Ids:
    53  	writer.Set(mockTextMapIdsPrefix+"traceid", strconv.Itoa(spanContext.TraceID))
    54  	writer.Set(mockTextMapIdsPrefix+"spanid", strconv.Itoa(spanContext.SpanID))
    55  	writer.Set(mockTextMapIdsPrefix+"sampled", fmt.Sprint(spanContext.Sampled))
    56  	// Baggage:
    57  	for baggageKey, baggageVal := range spanContext.Baggage {
    58  		safeVal := baggageVal
    59  		if t.HTTPHeaders {
    60  			safeVal = url.QueryEscape(baggageVal)
    61  		}
    62  		writer.Set(mockTextMapBaggagePrefix+baggageKey, safeVal)
    63  	}
    64  	return nil
    65  }
    66  
    67  // Extract implements the Extractor interface
    68  func (t *TextMapPropagator) Extract(carrier interface{}) (MockSpanContext, error) {
    69  	reader, ok := carrier.(opentracing.TextMapReader)
    70  	if !ok {
    71  		return emptyContext, opentracing.ErrInvalidCarrier
    72  	}
    73  	rval := MockSpanContext{0, 0, true, nil}
    74  	err := reader.ForeachKey(func(key, val string) error {
    75  		lowerKey := strings.ToLower(key)
    76  		switch {
    77  		case lowerKey == mockTextMapIdsPrefix+"traceid":
    78  			// Ids:
    79  			i, err := strconv.Atoi(val)
    80  			if err != nil {
    81  				return err
    82  			}
    83  			rval.TraceID = i
    84  		case lowerKey == mockTextMapIdsPrefix+"spanid":
    85  			// Ids:
    86  			i, err := strconv.Atoi(val)
    87  			if err != nil {
    88  				return err
    89  			}
    90  			rval.SpanID = i
    91  		case lowerKey == mockTextMapIdsPrefix+"sampled":
    92  			b, err := strconv.ParseBool(val)
    93  			if err != nil {
    94  				return err
    95  			}
    96  			rval.Sampled = b
    97  		case strings.HasPrefix(lowerKey, mockTextMapBaggagePrefix):
    98  			// Baggage:
    99  			if rval.Baggage == nil {
   100  				rval.Baggage = make(map[string]string)
   101  			}
   102  			safeVal := val
   103  			if t.HTTPHeaders {
   104  				// unescape errors are ignored, nothing can be done
   105  				if rawVal, err := url.QueryUnescape(val); err == nil {
   106  					safeVal = rawVal
   107  				}
   108  			}
   109  			rval.Baggage[lowerKey[len(mockTextMapBaggagePrefix):]] = safeVal
   110  		}
   111  		return nil
   112  	})
   113  	if rval.TraceID == 0 || rval.SpanID == 0 {
   114  		return emptyContext, opentracing.ErrSpanContextNotFound
   115  	}
   116  	if err != nil {
   117  		return emptyContext, err
   118  	}
   119  	return rval, nil
   120  }
   121
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