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// Copyright (c) 2019 The Jaeger Authors.
// Copyright (c) 2017 Uber Technologies, Inc.
//
// 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 tracing
import (
"net/http"
"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
"go.opentelemetry.io/otel/propagation"
"go.opentelemetry.io/otel/trace"
"go.uber.org/zap"
"github.com/jaegertracing/jaeger/examples/hotrod/pkg/log"
)
// NewServeMux creates a new TracedServeMux.
func NewServeMux(copyBaggage bool, tracer trace.TracerProvider, logger log.Factory) *TracedServeMux {
return &TracedServeMux{
mux: http.NewServeMux(),
copyBaggage: copyBaggage,
tracer: tracer,
logger: logger,
}
}
// TracedServeMux is a wrapper around http.ServeMux that instruments handlers for tracing.
type TracedServeMux struct {
mux *http.ServeMux
copyBaggage bool
tracer trace.TracerProvider
logger log.Factory
}
// Handle implements http.ServeMux#Handle, which is used to register new handler.
func (tm *TracedServeMux) Handle(pattern string, handler http.Handler) {
tm.logger.Bg().Debug("registering traced handler", zap.String("endpoint", pattern))
middleware := otelhttp.NewHandler(
otelhttp.WithRouteTag(pattern, traceResponseHandler(handler)),
pattern,
otelhttp.WithTracerProvider(tm.tracer))
tm.mux.Handle(pattern, middleware)
}
// ServeHTTP implements http.ServeMux#ServeHTTP.
func (tm *TracedServeMux) ServeHTTP(w http.ResponseWriter, r *http.Request) {
tm.mux.ServeHTTP(w, r)
}
// Returns a handler that generates a traceresponse header.
// https://github.com/w3c/trace-context/blob/main/spec/21-http_response_header_format.md
func traceResponseHandler(handler http.Handler) http.Handler {
// We use the standard TraceContext propagator, since the formats are identical.
// But the propagator uses "traceparent" header name, so we inject it into a map
// `carrier` and then use the result to set the "tracereponse" header.
var prop propagation.TraceContext
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
carrier := make(map[string]string)
prop.Inject(r.Context(), propagation.MapCarrier(carrier))
w.Header().Add("traceresponse", carrier["traceparent"])
handler.ServeHTTP(w, r)
})
}