From 73266df0f5e2508fb7276b99069a0e858ab8c45e Mon Sep 17 00:00:00 2001
From: TheFox0x7 <thefox0x7@gmail.com>
Date: Tue, 14 Jan 2025 00:01:21 +0100
Subject: [PATCH] feat(metrics): add cache, process and http metrics

---
 modules/cache/cache.go        | 22 ++++++++++++++++++++++
 modules/cache/string_cache.go |  6 ++++++
 routers/common/middleware.go  | 28 ++++++++++++++++++++++++++++
 routers/web/web.go            |  2 ++
 4 files changed, 58 insertions(+)

diff --git a/modules/cache/cache.go b/modules/cache/cache.go
index f7828e3cae2..49bb3bff9f8 100644
--- a/modules/cache/cache.go
+++ b/modules/cache/cache.go
@@ -9,11 +9,33 @@ import (
 	"time"
 
 	"code.gitea.io/gitea/modules/setting"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
 
 	_ "gitea.com/go-chi/cache/memcache" //nolint:depguard // memcache plugin for cache, it is required for config "ADAPTER=memcache"
 )
 
 var defaultCache StringCache
+var hitCounter = promauto.NewCounter(prometheus.CounterOpts{
+	Namespace: "gitea",
+	Help:      "Cache hit count",
+	Subsystem: "cache",
+	Name:      "hit",
+})
+var missCounter = promauto.NewCounter(prometheus.CounterOpts{
+	Namespace: "gitea",
+	Help:      "Cache miss count",
+	Subsystem: "cache",
+	Name:      "miss",
+})
+var latencyHistogram = promauto.NewHistogram(
+	prometheus.HistogramOpts{
+		Namespace: "gitea",
+		Help:      "Cache latency",
+		Subsystem: "cache",
+		Name:      "duration",
+	},
+)
 
 // Init start cache service
 func Init() error {
diff --git a/modules/cache/string_cache.go b/modules/cache/string_cache.go
index 4f659616f50..328cb6d2135 100644
--- a/modules/cache/string_cache.go
+++ b/modules/cache/string_cache.go
@@ -6,6 +6,7 @@ package cache
 import (
 	"errors"
 	"strings"
+	"time"
 
 	"code.gitea.io/gitea/modules/json"
 	"code.gitea.io/gitea/modules/setting"
@@ -63,10 +64,15 @@ func (sc *stringCache) Ping() error {
 }
 
 func (sc *stringCache) Get(key string) (string, bool) {
+	start := time.Now()
 	v := sc.chiCache.Get(key)
+	elapsed := time.Since(start).Seconds()
+	latencyHistogram.Observe(elapsed)
 	if v == nil {
+		missCounter.Add(1)
 		return "", false
 	}
+	hitCounter.Add(1)
 	s, ok := v.(string)
 	return s, ok
 }
diff --git a/routers/common/middleware.go b/routers/common/middleware.go
index 2ba02de8edc..739c92918aa 100644
--- a/routers/common/middleware.go
+++ b/routers/common/middleware.go
@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"net/http"
 	"strings"
+	"time"
 
 	"code.gitea.io/gitea/modules/cache"
 	"code.gitea.io/gitea/modules/gtprof"
@@ -19,8 +20,17 @@ import (
 	"gitea.com/go-chi/session"
 	"github.com/chi-middleware/proxy"
 	"github.com/go-chi/chi/v5"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
 )
 
+var responseLatency = promauto.NewHistogramVec(prometheus.HistogramOpts{
+	Namespace: "http",
+	Subsystem: "request",
+	Name:      "duration_seconds",
+	Help:      "Gitea response time",
+}, []string{"route"})
+
 // ProtocolMiddlewares returns HTTP protocol related middlewares, and it provides a global panic recovery
 func ProtocolMiddlewares() (handlers []any) {
 	// the order is important
@@ -38,6 +48,9 @@ func ProtocolMiddlewares() (handlers []any) {
 	if setting.IsAccessLogEnabled() {
 		handlers = append(handlers, context.AccessLogger())
 	}
+	if setting.Metrics.Enabled {
+		handlers = append(handlers, RouteMetrics())
+	}
 
 	return handlers
 }
@@ -107,6 +120,21 @@ func ForwardedHeadersHandler(limit int, trustedProxies []string) func(h http.Han
 	return proxy.ForwardedHeaders(opt)
 }
 
+func RouteMetrics() func(h http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(resp http.ResponseWriter, req *http.Request) {
+			start := time.Now()
+			next.ServeHTTP(resp, req)
+			elapsed := time.Since(start).Seconds()
+			route := "ui"
+			if strings.HasPrefix(req.URL.Path, "/api") {
+				route = "api"
+			}
+			responseLatency.WithLabelValues(route).Observe(elapsed)
+		})
+	}
+}
+
 func Sessioner() func(next http.Handler) http.Handler {
 	return session.Sessioner(session.Options{
 		Provider:       setting.SessionConfig.Provider,
diff --git a/routers/web/web.go b/routers/web/web.go
index ef26dd9a743..02167b60d75 100644
--- a/routers/web/web.go
+++ b/routers/web/web.go
@@ -52,6 +52,7 @@ import (
 	"github.com/go-chi/cors"
 	"github.com/klauspost/compress/gzhttp"
 	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/collectors"
 )
 
 var GzipMinSize = 1400 // min size to compress for the body size of response
@@ -258,6 +259,7 @@ func Routes() *web.Router {
 	}
 
 	if setting.Metrics.Enabled {
+		prometheus.MustRegister(collectors.NewProcessCollector(collectors.ProcessCollectorOpts{Namespace: "gitea"}))
 		prometheus.MustRegister(metrics.NewCollector())
 		routes.Get("/metrics", append(mid, Metrics)...)
 	}