vendor/go.opencensus.io/plugin/ochttp/route.go

   1 // Copyright 2018, OpenCensus Authors
   2 //
   3 // Licensed under the Apache License, Version 2.0 (the "License");
   4 // you may not use this file except in compliance with the License.
   5 // You may obtain a copy of the License at
   6 //
   7 //     http://www.apache.org/licenses/LICENSE-2.0
   8 //
   9 // Unless required by applicable law or agreed to in writing, software
  10 // distributed under the License is distributed on an "AS IS" BASIS,
  11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12 // See the License for the specific language governing permissions and
  13 // limitations under the License.
  14
  15 package ochttp
  16
  17 import (
  18         "net/http"
  19
  20         "go.opencensus.io/tag"
  21 )
  22
  23 // WithRouteTag returns an http.Handler that records stats with the
  24 // http_server_route tag set to the given value.
  25 func WithRouteTag(handler http.Handler, route string) http.Handler {
  26         return taggedHandlerFunc(func(w http.ResponseWriter, r *http.Request) []tag.Mutator {
  27                 addRoute := []tag.Mutator{tag.Upsert(KeyServerRoute, route)}
  28                 ctx, _ := tag.New(r.Context(), addRoute...)
  29                 r = r.WithContext(ctx)
  30                 handler.ServeHTTP(w, r)
  31                 return addRoute
  32         })
  33 }
  34
  35 // taggedHandlerFunc is a http.Handler that returns tags describing the
  36 // processing of the request. These tags will be recorded along with the
  37 // measures in this package at the end of the request.
  38 type taggedHandlerFunc func(w http.ResponseWriter, r *http.Request) []tag.Mutator
  39
  40 func (h taggedHandlerFunc) ServeHTTP(w http.ResponseWriter, r *http.Request) {
  41         tags := h(w, r)
  42         if a, ok := r.Context().Value(addedTagsKey{}).(*addedTags); ok {
  43                 a.t = append(a.t, tags...)
  44         }
  45 }
  46
  47 type addedTagsKey struct{}
  48
  49 type addedTags struct {
  50         t []tag.Mutator
  51 }