initial

.github/workflows/go.yaml

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+name: Go
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+jobs:
+  test:
+    name: Test
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install go
+        uses: actions/setup-go@v2
+        with:
+          go-version: 1.16
+
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Test
+        run: make test

.gitignore

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+.idea
+vendor
+cover.*

LICENSE

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+The MIT License (MIT)
+
+Copyright (c) 2022 Kaspar Birk
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Makefile

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+GOWORK=off
+
+build:
+	@go build ./...
+
+cover:
+	@go test -coverprofile=cover.out -covermode=atomic -coverpkg=./... ./...
+	@go tool cover -html=cover.out -o cover.html
+
+test:
+	@go test ./... -v
+
+doc:
+	@godoc -http=:6060

README.md

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+# promware [![Test Status](https://github.com/imbue11235/promware/workflows/Go/badge.svg)](https://github.com/imbue11235/promware/actions?query=workflow:Go) [![Go Reference](https://pkg.go.dev/badge/github.com/imbue11235/promware.svg)](https://pkg.go.dev/github.com/imbue11235/promware)
+
+> A simple, configurable middleware for recording request metrics with [Prometheus](https://github.com/prometheus/prometheus)
+
+## 🛠  Installation
+
+Make sure to have Go installed (Version `1.16` or higher).
+
+Install `promware` with `go get`:
+
+```sh
+$ go get -u github.com/imbue11235/promware
+```
+
+## 💻  Usage
+
+### With standard library
+
+```go
+middleware := promware.Default()
+
+handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+    w.WriteHeader(http.StatusOK)
+    fmt.Fprintln(w, "hello world")
+})
+
+mux := http.NewServeMux()
+mux.Handle("/metrics", promhttp.Handler())
+mux.Handle("/", middleware(handler))
+
+http.ListenAndServe("<addr>", mux)
+```
+
+### Options
+```go
+middleware := promware.New(
+    // Skip depending on request data 
+    promware.WithSkipFunc(func(r *http.Request) bool {
+        return r.URL.Path == "/something"
+    })
+
+    // Set subsystem
+    promware.WithSubsystem("my-subsystem")
+
+    // Set namespace 
+    promware.WithNamespace("my-namespace")
+
+    // Add request counter, set name
+    promware.WithRequestCounter("total-requests")
+
+    // Add latency histogram, set name and buckets
+    promware.WithLatencyHistogram("request-latency", []float64{0.5, 1, 2})
+)
+```
+
+## 📜 License
+
+This project is licensed under the [MIT license](LICENSE).

collector.go

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+package promware
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"net/http"
+)
+
+const defaultMetricsPath = "/metrics"
+
+// SkipFunc allows for certain requests to be skipped
+// based on information obtained from the http.Request, e.g. URLPath.
+type SkipFunc func(r *http.Request) bool
+
+// collector holds information and collectors needed by prometheus
+type collector struct {
+	namespace string
+	subsystem string
+
+	requestCounter   *prometheus.CounterVec
+	latencyHistogram *prometheus.HistogramVec
+
+	shouldSkip SkipFunc
+}
+
+// newCollector creates a new collector with empty values
+func newCollector() *collector {
+	return &collector{
+		namespace: "",
+		subsystem: "",
+		shouldSkip: func(r *http.Request) bool {
+			// default skips on `/metrics` endpoint, which
+			// is commonly used with Prometheus
+			return r.URL.Path == defaultMetricsPath
+		},
+	}
+}
+
+// apply adds options to the recorder
+func (c *collector) apply(options ...option) {
+	for _, opt := range options {
+		opt(c)
+	}
+}
+
+// register registers all the prometheus.Collectors
+func (c *collector) register() error {
+	collectors := []prometheus.Collector{
+		c.requestCounter,
+		c.latencyHistogram,
+	}
+
+	for _, collector := range collectors {
+		if collector == nil {
+			continue
+		}
+
+		if err := prometheus.Register(collector); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// addObservationToLatencyHistogram adds an observation to the latency histogram collector
+func (c *collector) addObservationToLatencyHistogram(code, method, path string, seconds float64) {
+	if c.latencyHistogram == nil {
+		return
+	}
+
+	c.latencyHistogram.WithLabelValues(code, method, path).Observe(seconds)
+}
+
+// incrementRequestCounter increments the current request counter collector by 1
+func (c *collector) incrementRequestCounter(code, method, path string) {
+	if c.requestCounter == nil {
+		return
+	}
+
+	c.requestCounter.WithLabelValues(code, method, path).Inc()
+}

examples/std/main.go

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+package main
+
+import (
+	"fmt"
+	"github.com/imbue11235/promware"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"log"
+	"net/http"
+)
+
+func main() {
+	addr := ":8080"
+
+	middleware := promware.Default()
+
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		fmt.Fprintln(w, "hello world")
+	})
+
+	mux := http.NewServeMux()
+	mux.Handle("/metrics", promhttp.Handler())
+	mux.Handle("/", middleware(handler))
+
+	log.Printf("Serving on addr %s", addr)
+
+	http.ListenAndServe(addr, mux)
+}

go.mod

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+module github.com/imbue11235/promware
+
+go 1.16
+
+require (
+	github.com/appleboy/gofight/v2 v2.1.2 // indirect
+	github.com/prometheus/client_golang v1.12.2
+	github.com/stretchr/testify v1.8.0 // indirect
+)