Source: route.go in package go.opencensus.io/plugin/ochttp

Copyright 2018, OpenCensus 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 ochttp

import (
	"context"
	"net/http"

	"go.opencensus.io/tag"
)

SetRoute sets the http_server_route tag to the given value. It's useful when an HTTP framework does not support the http.Handler interface and using WithRouteTag is not an option, but provides a way to hook into the request flow.

func SetRoute(ctx context.Context, route string) {
	if a, ok := ctx.Value(addedTagsKey{}).(*addedTags); ok {
		a.t = append(a.t, tag.Upsert(KeyServerRoute, route))
	}
}

WithRouteTag returns an http.Handler that records stats with the http_server_route tag set to the given value.

func WithRouteTag(handler http.Handler, route string) http.Handler {
	return taggedHandlerFunc(func(w http.ResponseWriter, r *http.Request) []tag.Mutator {
		addRoute := []tag.Mutator{tag.Upsert(KeyServerRoute, route)}
		ctx, _ := tag.New(r.Context(), addRoute...)
		r = r.WithContext(ctx)
		handler.ServeHTTP(w, r)
		return addRoute
	})
}

taggedHandlerFunc is a http.Handler that returns tags describing the processing of the request. These tags will be recorded along with the measures in this package at the end of the request.

type taggedHandlerFunc func(w http.ResponseWriter, r *http.Request) []tag.Mutator

func (h taggedHandlerFunc) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	tags := h(w, r)
	if a, ok := r.Context().Value(addedTagsKey{}).(*addedTags); ok {
		a.t = append(a.t, tags...)
	}
}

type addedTagsKey struct{}

type addedTags struct {
	t []tag.Mutator