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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 b3
import (
"google.golang.org/grpc/metadata"
"github.com/openzipkin/zipkin-go/model"
"github.com/openzipkin/zipkin-go/propagation"
)
// ExtractGRPC will extract a span.Context from the gRPC Request metadata if
// found in B3 header format.
func ExtractGRPC(md *metadata.MD) propagation.Extractor {
return func() (*model.SpanContext, error) {
var (
traceIDHeader = GetGRPCHeader(md, TraceID)
spanIDHeader = GetGRPCHeader(md, SpanID)
parentSpanIDHeader = GetGRPCHeader(md, ParentSpanID)
sampledHeader = GetGRPCHeader(md, Sampled)
flagsHeader = GetGRPCHeader(md, Flags)
)
return ParseHeaders(
traceIDHeader, spanIDHeader, parentSpanIDHeader, sampledHeader,
flagsHeader,
)
}
}
// InjectGRPC will inject a span.Context into gRPC metadata.
func InjectGRPC(md *metadata.MD) propagation.Injector {
return func(sc model.SpanContext) error {
if (model.SpanContext{}) == sc {
return ErrEmptyContext
}
if sc.Debug {
setGRPCHeader(md, Flags, "1")
} else if sc.Sampled != nil {
// Debug is encoded as X-B3-Flags: 1. Since Debug implies Sampled,
// we don't send "X-B3-Sampled" if Debug is set.
if *sc.Sampled {
setGRPCHeader(md, Sampled, "1")
} else {
setGRPCHeader(md, Sampled, "0")
}
}
if !sc.TraceID.Empty() && sc.ID > 0 {
// set identifiers
setGRPCHeader(md, TraceID, sc.TraceID.String())
setGRPCHeader(md, SpanID, sc.ID.String())
if sc.ParentID != nil {
setGRPCHeader(md, ParentSpanID, sc.ParentID.String())
}
}
return nil
}
}
// GetGRPCHeader retrieves the last value found for a particular key. If key is
// not found it returns an empty string.
func GetGRPCHeader(md *metadata.MD, key string) string {
v := (*md)[key]
if len(v) < 1 {
return ""
}
return v[len(v)-1]
}
func setGRPCHeader(md *metadata.MD, key, value string) {
(*md)[key] = append((*md)[key], value)
}
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