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// Copyright 2022 The OpenZipkin Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package grpc
import (
"context"
"google.golang.org/grpc/metadata"
"google.golang.org/grpc/stats"
"github.com/openzipkin/zipkin-go"
"github.com/openzipkin/zipkin-go/model"
"github.com/openzipkin/zipkin-go/propagation/b3"
)
type clientHandler struct {
tracer *zipkin.Tracer
remoteServiceName string
}
// A ClientOption can be passed to NewClientHandler to customize the returned handler.
type ClientOption func(*clientHandler)
// WithRemoteServiceName will set the value for the remote endpoint's service name on
// all spans.
func WithRemoteServiceName(name string) ClientOption {
return func(c *clientHandler) {
c.remoteServiceName = name
}
}
// NewClientHandler returns a stats.Handler which can be used with grpc.WithStatsHandler to add
// tracing to a gRPC client. 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.
func NewClientHandler(tracer *zipkin.Tracer, options ...ClientOption) stats.Handler {
c := &clientHandler{
tracer: tracer,
}
for _, option := range options {
option(c)
}
return c
}
// HandleConn exists to satisfy gRPC stats.Handler.
func (c *clientHandler) HandleConn(_ context.Context, _ stats.ConnStats) {
// no-op
}
// TagConn exists to satisfy gRPC stats.Handler.
func (c *clientHandler) TagConn(ctx context.Context, _ *stats.ConnTagInfo) context.Context {
// no-op
return ctx
}
// HandleRPC implements per-RPC tracing and stats instrumentation.
func (c *clientHandler) HandleRPC(ctx context.Context, rs stats.RPCStats) {
handleRPC(ctx, rs)
}
// TagRPC implements per-RPC context management.
func (c *clientHandler) TagRPC(ctx context.Context, rti *stats.RPCTagInfo) context.Context {
var span zipkin.Span
ep := remoteEndpointFromContext(ctx, c.remoteServiceName)
name := spanName(rti)
span, ctx = c.tracer.StartSpanFromContext(ctx, name, zipkin.Kind(model.Client), zipkin.RemoteEndpoint(ep))
md, ok := metadata.FromOutgoingContext(ctx)
if ok {
md = md.Copy()
} else {
md = metadata.New(nil)
}
_ = b3.InjectGRPC(&md)(span.Context())
// inject baggage fields from span context into the outgoing gRPC request metadata
if span.Context().Baggage != nil {
span.Context().Baggage.Iterate(func(key string, values []string) {
md.Set(key, values...)
})
}
ctx = metadata.NewOutgoingContext(ctx, md)
return ctx
}
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