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// Copyright 2022 The Prometheus 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 httpmiddleware is adapted from
// https://github.com/bwplotka/correlator/tree/main/examples/observability/ping/pkg/httpinstrumentation
package httpmiddleware
import (
"net/http"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promauto"
"github.com/prometheus/client_golang/prometheus/promhttp"
)
type Middleware interface {
// WrapHandler wraps the given HTTP handler for instrumentation.
WrapHandler(handlerName string, handler http.Handler) http.HandlerFunc
}
type middleware struct {
buckets []float64
registry prometheus.Registerer
}
// WrapHandler wraps the given HTTP handler for instrumentation:
// It registers four metric collectors (if not already done) and reports HTTP
// metrics to the (newly or already) registered collectors.
// Each has a constant label named "handler" with the provided handlerName as
// value.
func (m *middleware) WrapHandler(handlerName string, handler http.Handler) http.HandlerFunc {
reg := prometheus.WrapRegistererWith(prometheus.Labels{"handler": handlerName}, m.registry)
requestsTotal := promauto.With(reg).NewCounterVec(
prometheus.CounterOpts{
Name: "http_requests_total",
Help: "Tracks the number of HTTP requests.",
}, []string{"method", "code"},
)
requestDuration := promauto.With(reg).NewHistogramVec(
prometheus.HistogramOpts{
Name: "http_request_duration_seconds",
Help: "Tracks the latencies for HTTP requests.",
Buckets: m.buckets,
},
[]string{"method", "code"},
)
requestSize := promauto.With(reg).NewSummaryVec(
prometheus.SummaryOpts{
Name: "http_request_size_bytes",
Help: "Tracks the size of HTTP requests.",
},
[]string{"method", "code"},
)
responseSize := promauto.With(reg).NewSummaryVec(
prometheus.SummaryOpts{
Name: "http_response_size_bytes",
Help: "Tracks the size of HTTP responses.",
},
[]string{"method", "code"},
)
// Wraps the provided http.Handler to observe the request result with the provided metrics.
base := promhttp.InstrumentHandlerCounter(
requestsTotal,
promhttp.InstrumentHandlerDuration(
requestDuration,
promhttp.InstrumentHandlerRequestSize(
requestSize,
promhttp.InstrumentHandlerResponseSize(
responseSize,
handler,
),
),
),
)
return base.ServeHTTP
}
// New returns a Middleware interface.
func New(registry prometheus.Registerer, buckets []float64) Middleware {
if buckets == nil {
buckets = prometheus.ExponentialBuckets(0.1, 1.5, 5)
}
return &middleware{
buckets: buckets,
registry: registry,
}
}
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