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mux.go
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mux.go
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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"
"github.com/opentracing-contrib/go-stdlib/nethttp"
"github.com/opentracing/opentracing-go"
"go.opentelemetry.io/otel/baggage"
"go.opentelemetry.io/otel/propagation"
"go.uber.org/zap"
"github.com/jaegertracing/jaeger/examples/hotrod/pkg/log"
)
// NewServeMux creates a new TracedServeMux.
func NewServeMux(copyBaggage bool, tracer opentracing.Tracer, 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 opentracing.Tracer
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 := nethttp.Middleware(
tm.tracer,
handler,
nethttp.OperationNameFunc(func(r *http.Request) string {
return "HTTP " + r.Method + " " + pattern
}),
// Jaeger SDK was able to accept `jaeger-baggage` header even for requests without am active trace.
// OTEL Bridge does not support that, so we use Baggage propagator to manually extract the baggage
// into Context (in otelBaggageExtractor handler below), and once the Bridge creates a Span,
// we use this SpanObserver to copy OTEL baggage from Context into the Span.
nethttp.MWSpanObserver(func(span opentracing.Span, r *http.Request) {
if !tm.copyBaggage {
return
}
bag := baggage.FromContext(r.Context())
for _, m := range bag.Members() {
if b := span.BaggageItem(m.Key()); b == "" {
span.SetBaggageItem(m.Key(), m.Value())
}
}
}),
)
tm.mux.Handle(pattern, otelBaggageExtractor(middleware))
}
// ServeHTTP implements http.ServeMux#ServeHTTP.
func (tm *TracedServeMux) ServeHTTP(w http.ResponseWriter, r *http.Request) {
tm.mux.ServeHTTP(w, r)
}
// Used with nethttp.MWSpanObserver above.
func otelBaggageExtractor(next http.Handler) http.Handler {
propagator := propagation.Baggage{}
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
carrier := propagation.HeaderCarrier(r.Header)
ctx := propagator.Extract(r.Context(), carrier)
r = r.WithContext(ctx)
next.ServeHTTP(w, r)
})
}