129 lines
3.8 KiB
Go
129 lines
3.8 KiB
Go
// Copyright 2022 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package promhttp
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import (
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"context"
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"log"
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"net/http"
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"github.com/prometheus/client_golang/prometheus"
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)
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type key int
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const (
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CtxResolverKey key = iota
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)
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func ExampleInstrumentHandlerWithExtraMethods() {
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counter := prometheus.NewCounterVec(
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prometheus.CounterOpts{
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Name: "api_requests_total",
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Help: "A counter for requests to the wrapped handler.",
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},
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[]string{"code", "method"},
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)
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// duration is partitioned by the HTTP method and handler. It uses custom
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// buckets based on the expected request duration.
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duration := prometheus.NewHistogramVec(
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prometheus.HistogramOpts{
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Name: "request_duration_seconds",
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Help: "A histogram of latencies for requests.",
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Buckets: []float64{.25, .5, 1, 2.5, 5, 10},
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},
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[]string{"handler", "method"},
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)
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// Create the handlers that will be wrapped by the middleware.
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pullHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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w.Write([]byte("Pull"))
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})
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// Specify additional HTTP methods to be added to the label allow list.
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opts := WithExtraMethods("CUSTOM_METHOD")
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// Instrument the handlers with all the metrics, injecting the "handler"
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// label by currying.
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pullChain := InstrumentHandlerDuration(duration.MustCurryWith(prometheus.Labels{"handler": "pull"}),
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InstrumentHandlerCounter(counter, pullHandler, opts),
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opts,
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)
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http.Handle("/metrics", Handler())
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http.Handle("/pull", pullChain)
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if err := http.ListenAndServe(":3000", nil); err != nil {
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log.Fatal(err)
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}
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}
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func ExampleInstrumentHandlerWithLabelResolver() {
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counter := prometheus.NewCounterVec(
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prometheus.CounterOpts{
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Name: "api_requests_total",
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Help: "A counter for requests to the wrapped handler.",
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},
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[]string{"code", "method", "myheader"},
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)
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// duration is partitioned by the HTTP method, handler and request header
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// value. It uses custom buckets based on the expected request duration.
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// Beware to not have too high cardinality on the values of header. You
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// always should sanitize external inputs.
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duration := prometheus.NewHistogramVec(
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prometheus.HistogramOpts{
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Name: "request_duration_seconds",
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Help: "A histogram of latencies for requests.",
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Buckets: []float64{.25, .5, 1, 2.5, 5, 10},
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},
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[]string{"handler", "method", "myheader"},
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)
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// Create the handlers that will be wrapped by the middleware.
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pullHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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w.Write([]byte("Pull"))
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})
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// Specify additional HTTP methods to be added to the label allow list.
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opts := WithLabelFromCtx("myheader",
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func(ctx context.Context) string {
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return ctx.Value(CtxResolverKey).(string)
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},
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)
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// Instrument the handlers with all the metrics, injecting the "handler"
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// label by currying.
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pullChain := InstrumentHandlerDuration(duration.MustCurryWith(prometheus.Labels{"handler": "pull"}),
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InstrumentHandlerCounter(counter, pullHandler, opts),
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opts,
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)
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middleware := func(next http.HandlerFunc) http.HandlerFunc {
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return func(w http.ResponseWriter, r *http.Request) {
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ctx := context.WithValue(r.Context(), CtxResolverKey, r.Header.Get("x-my-header"))
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next(w, r.WithContext(ctx))
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}
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}
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http.Handle("/metrics", Handler())
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http.Handle("/pull", middleware(pullChain))
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if err := http.ListenAndServe(":3000", nil); err != nil {
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log.Fatal(err)
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}
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}
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