Add option to start http server for profiling (#323)

https://rafallorenz.com/go/go-profiling-http-service-with-pprof-and-expvar/
Reviewed-on: https://codeberg.org/Codeberg/pages-server/pulls/323
Co-authored-by: crapStone <me@crapstone.dev>
Co-committed-by: crapStone <me@crapstone.dev>

Justfile

@@ -1,13 +1,13 @@
 CGO_FLAGS := '-extldflags "-static" -linkmode external'
 TAGS      := 'sqlite sqlite_unlock_notify netgo'
 
-dev:
+dev *FLAGS:
     #!/usr/bin/env bash
     set -euxo pipefail
     set -a # automatically export all variables
     source .env-dev
     set +a
-    go run -tags '{{TAGS}}' .
+    go run -tags '{{TAGS}}' . {{FLAGS}}
 
 build:
     CGO_ENABLED=1 go build -tags '{{TAGS}}' -ldflags '-s -w {{CGO_FLAGS}}' -v -o build/codeberg-pages-server ./

README.md

@@ -124,3 +124,18 @@ now these pages should work:
 - <https://momar.localhost.mock.directory:4430/ci-testing/>
 - <https://momar.localhost.mock.directory:4430/pag/@master/>
 - <https://mock-pages.codeberg-test.org:4430/README.md>
+
+### Profiling
+
+> This section is just a collection of commands for quick reference. If you want to learn more about profiling read [this](https://go.dev/doc/diagnostics) article or google `golang profiling`.
+
+First enable profiling by supplying the cli arg `--enable-profiling` or using the environment variable `EENABLE_PROFILING`.
+
+Get cpu and mem stats:
+
+```bash
+go tool pprof -raw -output=cpu.txt 'http://localhost:9999/debug/pprof/profile?seconds=60' &
+curl -so mem.txt 'http://localhost:9999/debug/pprof/heap?seconds=60'
+```
+
+More endpoints are documented here: <https://pkg.go.dev/net/http/pprof>

cli/flags.go

@@ -139,6 +139,18 @@ var (
 			EnvVars: []string{"CONFIG_FILE"},
 		},
 
+		&cli.BoolFlag{
+			Name:    "enable-profiling",
+			Usage:   "enables the go http profiling endpoints",
+			EnvVars: []string{"ENABLE_PROFILING"},
+		},
+		&cli.StringFlag{
+			Name:    "profiling-address",
+			Usage:   "specify ip address and port the profiling server should listen on",
+			EnvVars: []string{"PROFILING_ADDRESS"},
+			Value:   "localhost:9999",
+		},
+
 		// ############################
 		// ### ACME Client Settings ###
 		// ############################

server/profiling.go

@@ -0,0 +1,21 @@
+package server
+
+import (
+	"net/http"
+	_ "net/http/pprof"
+
+	"github.com/rs/zerolog/log"
+)
+
+func StartProfilingServer(listeningAddress string) {
+	server := &http.Server{
+		Addr:    listeningAddress,
+		Handler: http.DefaultServeMux,
+	}
+
+	log.Info().Msgf("Starting debug server on %s", listeningAddress)
+
+	go func() {
+		log.Fatal().Err(server.ListenAndServe()).Msg("Failed to start debug server")
+	}()
+}

server/startup.go

@@ -3,7 +3,6 @@ package server
 import (
 	"context"
 	"crypto/tls"
-	"encoding/json"
 	"fmt"
 	"net"
 	"net/http"
@@ -43,9 +42,6 @@ func Serve(ctx *cli.Context) error {
 	}
 	log.Logger = zerolog.New(zerolog.ConsoleWriter{Out: os.Stderr}).With().Timestamp().Logger().Level(logLevel)
 
-	foo, _ := json.Marshal(cfg)
-	log.Trace().RawJSON("config", foo).Msg("starting server with config")
-
 	listeningSSLAddress := fmt.Sprintf("%s:%d", cfg.Server.Host, cfg.Server.Port)
 	listeningHTTPAddress := fmt.Sprintf("%s:%d", cfg.Server.Host, cfg.Server.HttpPort)
 
@@ -133,6 +129,10 @@ func Serve(ctx *cli.Context) error {
 		}()
 	}
 
+	if ctx.IsSet("enable-profiling") {
+		StartProfilingServer(ctx.String("profiling-address"))
+	}
+
 	// Create ssl handler based on settings
 	sslHandler := handler.Handler(cfg.Server, giteaClient, dnsLookupCache, canonicalDomainCache, redirectsCache)