Using pprof to find memory leaks for golang binaries

README.md

1. run the main.go using go run main.go
2. find the pid of the process and send a USR1 signal using kill -USR1 pid-of-main
3. the heap_profile.pprof will be generated in the directory the main process was running
4. run go tool pprof -http=:8081 heap_profile.pprof to visualize the heap

main.go

package main

import (
	"fmt"
	"math/rand"
	"os"
	"os/signal"
	"runtime/pprof"
	"sync"
	"syscall"
	"time"
)

func setupSignalHandlerForHeapProfile() {
	// Set up signal handler
	sigChan := make(chan os.Signal, 1)
	signal.Notify(sigChan, syscall.SIGUSR1)

	go func() {
		for {
			<-sigChan
			// Generate heap profile when SIGUSR1 is received
			f, _ := os.Create("heap_profile.pprof")
			pprof.WriteHeapProfile(f)
			f.Close()
		}
	}()
}

func main() {
	setupSignalHandlerForHeapProfile()

	cache := &Cache{
		items: make(map[string]*Resource),
	}

	var wg sync.WaitGroup
	for i := 0; i < 100; i++ {
		wg.Add(1)
		go leakyGoroutine(&wg, cache)
	}

	ticker := time.NewTicker(5 * time.Second)
	defer ticker.Stop()

	go func() {
		for range ticker.C {
			fmt.Printf("Cache size: %d\n", len(cache.items))
		}
	}()

	wg.Wait() // This will never complete
}

type Resource struct {
	data []byte
}

type Cache struct {
	mu    sync.Mutex
	items map[string]*Resource
}

func (c *Cache) Set(key string, value *Resource) {
	c.mu.Lock()
	defer c.mu.Unlock()
	c.items[key] = value
}

func (c *Cache) Get(key string) *Resource {
	c.mu.Lock()
	defer c.mu.Unlock()
	return c.items[key]
}

func leakyGoroutine(wg *sync.WaitGroup, cache *Cache) {
	defer wg.Done()
	for {
		key := fmt.Sprintf("key-%d", rand.Intn(1000))
		resource := &Resource{
			data: make([]byte, 1024*1024), // Allocate 1MB
		}
		cache.Set(key, resource)
		time.Sleep(time.Millisecond * 100)
	}
}