grpc.go

Documentation: github.com/go-kit/kit/tracing/opentracing

     1  package opentracing
     2  
     3  import (
     4  	"context"
     5  	"encoding/base64"
     6  	"strings"
     7  
     8  	"github.com/opentracing/opentracing-go"
     9  	"github.com/opentracing/opentracing-go/ext"
    10  	"google.golang.org/grpc/metadata"
    11  
    12  	"github.com/go-kit/log"
    13  )
    14  
    15  // ContextToGRPC returns a grpc RequestFunc that injects an OpenTracing Span
    16  // found in `ctx` into the grpc Metadata. If no such Span can be found, the
    17  // RequestFunc is a noop.
    18  func ContextToGRPC(tracer opentracing.Tracer, logger log.Logger) func(ctx context.Context, md *metadata.MD) context.Context {
    19  	return func(ctx context.Context, md *metadata.MD) context.Context {
    20  		if span := opentracing.SpanFromContext(ctx); span != nil {
    21  			// There's nothing we can do with an error here.
    22  			if err := tracer.Inject(span.Context(), opentracing.TextMap, metadataReaderWriter{md}); err != nil {
    23  				logger.Log("err", err)
    24  			}
    25  		}
    26  		return ctx
    27  	}
    28  }
    29  
    30  // GRPCToContext returns a grpc RequestFunc that tries to join with an
    31  // OpenTracing trace found in `req` and starts a new Span called
    32  // `operationName` accordingly. If no trace could be found in `req`, the Span
    33  // will be a trace root. The Span is incorporated in the returned Context and
    34  // can be retrieved with opentracing.SpanFromContext(ctx).
    35  func GRPCToContext(tracer opentracing.Tracer, operationName string, logger log.Logger) func(ctx context.Context, md metadata.MD) context.Context {
    36  	return func(ctx context.Context, md metadata.MD) context.Context {
    37  		var span opentracing.Span
    38  		wireContext, err := tracer.Extract(opentracing.TextMap, metadataReaderWriter{&md})
    39  		if err != nil && err != opentracing.ErrSpanContextNotFound {
    40  			logger.Log("err", err)
    41  		}
    42  		span = tracer.StartSpan(operationName, ext.RPCServerOption(wireContext))
    43  		return opentracing.ContextWithSpan(ctx, span)
    44  	}
    45  }
    46  
    47  // A type that conforms to opentracing.TextMapReader and
    48  // opentracing.TextMapWriter.
    49  type metadataReaderWriter struct {
    50  	*metadata.MD
    51  }
    52  
    53  func (w metadataReaderWriter) Set(key, val string) {
    54  	key = strings.ToLower(key)
    55  	if strings.HasSuffix(key, "-bin") {
    56  		val = base64.StdEncoding.EncodeToString([]byte(val))
    57  	}
    58  	(*w.MD)[key] = append((*w.MD)[key], val)
    59  }
    60  
    61  func (w metadataReaderWriter) ForeachKey(handler func(key, val string) error) error {
    62  	for k, vals := range *w.MD {
    63  		for _, v := range vals {
    64  			if err := handler(k, v); err != nil {
    65  				return err
    66  			}
    67  		}
    68  	}
    69  	return nil
    70  }
    71
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