From b511fad9682ce373c484070ef5b785b1302370c7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sybren=20A=2E=20St=C3=BCvel?= <sybren@blender.org>
Date: Fri, 15 Jul 2022 14:43:48 +0200
Subject: [PATCH] Manager: add profiler support

Add a `-pprof` CLI option to enable the profiler. It will expose profiler
info on the web interface at `/debug/pprof/`.

To have a nice view of this, including flame graphs, run:

```
go tool pprof -http localhost:8082 http://localhost:8080/debug/pprof/profile
```
---
 cmd/flamenco-manager/main.go | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/cmd/flamenco-manager/main.go b/cmd/flamenco-manager/main.go
index 6b4b5ca4..b2e65ef6 100644
--- a/cmd/flamenco-manager/main.go
+++ b/cmd/flamenco-manager/main.go
@@ -11,10 +11,12 @@ import (
 	"math/rand"
 	"net"
 	"net/http"
+	http_pprof "net/http/pprof"
 	"net/url"
 	"os"
 	"os/signal"
 	"runtime"
+	"runtime/pprof"
 	"strings"
 	"sync"
 	"syscall"
@@ -55,6 +57,7 @@ var cliArgs struct {
 	writeConfig     bool
 	delayResponses  bool
 	firstTimeWizard bool
+	pprof           bool
 }
 
 const (
@@ -381,6 +384,20 @@ func buildWebService(
 		return c.Redirect(http.StatusTemporaryRedirect, "/app/")
 	})
 
+	// Register profiler functions.
+	if cliArgs.pprof {
+		e.GET("/debug/pprof/", echo.WrapHandler(http.HandlerFunc(http_pprof.Index)))
+		e.GET("/debug/pprof/cmdline", echo.WrapHandler(http.HandlerFunc(http_pprof.Cmdline)))
+		e.GET("/debug/pprof/profile", echo.WrapHandler(http.HandlerFunc(http_pprof.Profile)))
+		e.GET("/debug/pprof/symbol", echo.WrapHandler(http.HandlerFunc(http_pprof.Symbol)))
+		e.GET("/debug/pprof/trace", echo.WrapHandler(http.HandlerFunc(http_pprof.Trace)))
+		for _, profile := range pprof.Profiles() {
+			name := profile.Name()
+			e.GET("/debug/pprof/"+name, echo.WrapHandler(http_pprof.Handler(name)))
+		}
+		log.Info().Msg("profiler debugging info available on /debug/pprof/")
+	}
+
 	// Log available routes
 	routeLogger := log.Level(zerolog.TraceLevel)
 	routeLogger.Trace().Msg("available routes:")
@@ -476,6 +493,7 @@ func parseCliArgs() {
 	flag.BoolVar(&cliArgs.delayResponses, "delay", false,
 		"Add a random delay to any HTTP responses. This aids in development of Flamenco Manager's web frontend.")
 	flag.BoolVar(&cliArgs.firstTimeWizard, "wizard", false, "Open a webbrowser with the first-time configuration wizard.")
+	flag.BoolVar(&cliArgs.pprof, "pprof", false, "Expose profiler endpoints on /debug/pprof/.")
 
 	flag.Parse()