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package grpc
import (
"context"
"github.com/openzipkin/zipkin-go"
"github.com/openzipkin/zipkin-go/model"
"github.com/openzipkin/zipkin-go/propagation/b3"
"google.golang.org/grpc/metadata"
"google.golang.org/grpc/stats"
)
type serverHandler struct {
tracer *zipkin.Tracer
defaultTags map[string]string
}
// A ServerOption can be passed to NewServerHandler to customize the returned handler.
type ServerOption func(*serverHandler)
// ServerTags adds default Tags to inject into server spans.
func ServerTags(tags map[string]string) ServerOption {
return func(h *serverHandler) {
h.defaultTags = tags
}
}
// NewServerHandler returns a stats.Handler which can be used with grpc.WithStatsHandler to add
// tracing to a gRPC server. The gRPC method name is used as the span name and by default the only
// tags are the gRPC status code if the call fails. Use ServerTags to add additional tags that
// should be applied to all spans.
func NewServerHandler(tracer *zipkin.Tracer, options ...ServerOption) stats.Handler {
c := &serverHandler{
tracer: tracer,
}
for _, option := range options {
option(c)
}
return c
}
// HandleConn exists to satisfy gRPC stats.Handler.
func (s *serverHandler) HandleConn(ctx context.Context, cs stats.ConnStats) {
// no-op
}
// TagConn exists to satisfy gRPC stats.Handler.
func (s *serverHandler) TagConn(ctx context.Context, cti *stats.ConnTagInfo) context.Context {
// no-op
return ctx
}
// HandleRPC implements per-RPC tracing and stats instrumentation.
func (s *serverHandler) HandleRPC(ctx context.Context, rs stats.RPCStats) {
handleRPC(ctx, rs)
}
// TagRPC implements per-RPC context management.
func (s *serverHandler) TagRPC(ctx context.Context, rti *stats.RPCTagInfo) context.Context {
md, ok := metadata.FromIncomingContext(ctx)
// In practice, ok never seems to be false but add a defensive check.
if !ok {
md = metadata.New(nil)
}
name := spanName(rti)
sc := s.tracer.Extract(b3.ExtractGRPC(&md))
span := s.tracer.StartSpan(name, zipkin.Kind(model.Server), zipkin.Parent(sc), zipkin.RemoteEndpoint(remoteEndpointFromContext(ctx, "")))
for k, v := range s.defaultTags {
span.Tag(k, v)
}
return zipkin.NewContext(ctx, span)
}
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