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119 lines
3.6 KiB
Go
119 lines
3.6 KiB
Go
package metrics
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import (
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"context"
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"github.com/prometheus/client_golang/prometheus"
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"github.com/prometheus/client_golang/prometheus/promauto"
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"github.com/prometheus/client_golang/prometheus/promhttp"
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"net/http"
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)
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// 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 metrics is adapted from
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// https://github.com/bwplotka/correlator/tree/main/examples/observability/ping/pkg/httpinstrumentation
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// https://github.com/prometheus/client_golang/blob/main/examples/middleware/httpmiddleware/httpmiddleware.go
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type Middleware interface {
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// WrapHandler wraps the given HTTP handler for instrumentation.
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WrapHandler(handlerName string, handler http.Handler) http.HandlerFunc
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}
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type middleware struct {
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buckets []float64
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registry prometheus.Registerer
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}
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// WrapHandler wraps the given HTTP handler for instrumentation:
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// It registers four metric collectors (if not already done) and reports HTTP
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// metrics to the (newly or already) registered collectors.
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// Each has a constant label named "handler" with the provided handlerName as
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// value.
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func (m *middleware) WrapHandler(handlerName string, handler http.Handler) http.HandlerFunc {
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reg := prometheus.WrapRegistererWith(prometheus.Labels{"handler": handlerName}, m.registry)
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requestsTotal := promauto.With(reg).NewCounterVec(
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prometheus.CounterOpts{
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Name: "http_requests_total",
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Help: "Tracks the number of HTTP requests.",
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}, []string{"method", "code", "host"},
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)
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requestDuration := promauto.With(reg).NewHistogramVec(
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prometheus.HistogramOpts{
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Name: "http_request_duration_seconds",
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Help: "Tracks the latencies for HTTP requests.",
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Buckets: m.buckets,
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},
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[]string{"method", "code", "host"},
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)
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requestSize := promauto.With(reg).NewSummaryVec(
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prometheus.SummaryOpts{
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Name: "http_request_size_bytes",
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Help: "Tracks the size of HTTP requests.",
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},
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[]string{"method", "code", "host"},
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)
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responseSize := promauto.With(reg).NewSummaryVec(
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prometheus.SummaryOpts{
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Name: "http_response_size_bytes",
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Help: "Tracks the size of HTTP responses.",
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},
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[]string{"method", "code", "host"},
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)
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hostCtxGetter := promhttp.WithLabelFromCtx("host", func(ctx context.Context) string {
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s, _ := ctx.Value(hostCtxKey(0)).(string)
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return s
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})
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// Wraps the provided http.Handler to observe the request result with the provided metrics.
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base := promhttp.InstrumentHandlerCounter(
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requestsTotal,
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promhttp.InstrumentHandlerDuration(
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requestDuration,
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promhttp.InstrumentHandlerRequestSize(
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requestSize,
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promhttp.InstrumentHandlerResponseSize(
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responseSize,
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handler,
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hostCtxGetter,
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),
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hostCtxGetter,
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),
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hostCtxGetter,
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),
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hostCtxGetter,
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)
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return base.ServeHTTP
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}
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// New returns a Middleware interface.
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func New(registry prometheus.Registerer, buckets []float64) Middleware {
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if buckets == nil {
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buckets = prometheus.ExponentialBuckets(0.1, 1.5, 5)
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}
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return &middleware{
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buckets: buckets,
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registry: registry,
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}
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}
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type hostCtxKey uint8
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func AddHostCtx(req *http.Request) *http.Request {
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return req.WithContext(context.WithValue(req.Context(), hostCtxKey(0), req.Host))
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}
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