8 "github.com/opentracing/opentracing-go"
9 "github.com/opentracing/opentracing-go/ext"
10 "google.golang.org/grpc/metadata"
12 "github.com/go-kit/kit/log"
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)
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)
42 span = tracer.StartSpan(operationName, ext.RPCServerOption(wireContext))
43 return opentracing.ContextWithSpan(ctx, span)
47 // A type that conforms to opentracing.TextMapReader and
48 // opentracing.TextMapWriter.
49 type metadataReaderWriter struct {
53 func (w metadataReaderWriter) Set(key, val string) {
54 key = strings.ToLower(key)
55 if strings.HasSuffix(key, "-bin") {
56 val = string(base64.StdEncoding.EncodeToString([]byte(val)))
58 (*w.MD)[key] = append((*w.MD)[key], val)
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 {