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 "context" 19 "net/http" 20 21 "go.opencensus.io/tag" 22 ) 23 24 // SetRoute sets the http_server_route tag to the given value. 25 // It's useful when an HTTP framework does not support the http.Handler interface 26 // and using WithRouteTag is not an option, but provides a way to hook into the request flow. 27 func SetRoute(ctx context.Context, route string) { 28 if a, ok := ctx.Value(addedTagsKey{}).(*addedTags); ok { 29 a.t = append(a.t, tag.Upsert(KeyServerRoute, route)) 30 } 31 } 32 33 // WithRouteTag returns an http.Handler that records stats with the 34 // http_server_route tag set to the given value. 35 func WithRouteTag(handler http.Handler, route string) http.Handler { 36 return taggedHandlerFunc(func(w http.ResponseWriter, r *http.Request) []tag.Mutator { 37 addRoute := []tag.Mutator{tag.Upsert(KeyServerRoute, route)} 38 ctx, _ := tag.New(r.Context(), addRoute...) 39 r = r.WithContext(ctx) 40 handler.ServeHTTP(w, r) 41 return addRoute 42 }) 43 } 44 45 // taggedHandlerFunc is a http.Handler that returns tags describing the 46 // processing of the request. These tags will be recorded along with the 47 // measures in this package at the end of the request. 48 type taggedHandlerFunc func(w http.ResponseWriter, r *http.Request) []tag.Mutator 49 50 func (h taggedHandlerFunc) ServeHTTP(w http.ResponseWriter, r *http.Request) { 51 tags := h(w, r) 52 if a, ok := r.Context().Value(addedTagsKey{}).(*addedTags); ok { 53 a.t = append(a.t, tags...) 54 } 55 } 56 57 type addedTagsKey struct{} 58 59 type addedTags struct { 60 t []tag.Mutator 61 } 62