golang run gc sample

go_gc.go

package main

import (
	"fmt"
	"net/http"
	"runtime"
	"strconv"
	"strings"
	"time"
)

type S struct {
	id    int
	num   int
	value string
}

var m map[string]*S

func init() {
	m = make(map[string]*S)
}

func main() {
	go server()

	fin := make(chan bool)
	go loop(fin)
	go mem(fin)
	<-fin
	<-fin
	fmt.Println("done")
}

func loop(c chan bool) {

	snooze := time.NewTicker(1 * time.Second)

	mem := time.Tick(9 * time.Second)

	after := time.After(5 * time.Minute)

	//sec := 0

	go func() {
		for {
			select {
			case <-snooze.C:
				//fmt.Print(sec, " ")
				//sec += 1
			case <-mem:
				go func() {
					fmt.Println("start putting to heap")
					for i := 0; i < 10000000; i++ {
						key := fmt.Sprintf("key_%d", i)
						m[key] = &S{id: i, num: i, value: "foo"}
					}
					fmt.Println("done to put")
					m = make(map[string]*S)
					
					fmt.Println("run GC")
					runtime.GC()
				}()
			}
		}
	}()

	<-after
	snooze.Stop()

	c <- true
}

func numberFormat(v uint64) string {
	s := strconv.FormatUint(v, 10)
	leftLen := len(s) % 3
	rightBlock := len(s) / 3

	var str []string
	if leftLen > 0 {
		left := s[0:leftLen]
		str = append(str, left)
	}

	for i := 0; i < rightBlock; i++ {
		base := i*3 + leftLen
		b := s[base : base+3]
		str = append(str, b)
	}
	return strings.Join(str, ",")
}

func mem(c chan bool) {
	snooze := time.NewTicker(1 * time.Second)
	fin := time.After(5 * time.Minute)
	go func() {
		for {
			select {
			case <-snooze.C:
				var mem runtime.MemStats
				runtime.ReadMemStats(&mem)
				
				fmt.Printf("Memory Stats:: Heap Allocated: %s, Heap Idle: %s, Heap In Use: %s, Heap Objects: %s\n",
					numberFormat(mem.HeapAlloc), numberFormat(mem.HeapIdle), numberFormat(mem.HeapInuse), numberFormat(mem.HeapObjects))
			}
		}
	}()
	<-fin
	snooze.Stop()
	c <- true
}

func server() {
	fmt.Println("start server:: localhost:18080")
	http.HandleFunc("/", handler)
	err := http.ListenAndServe(":18080", nil)
	if err != nil {
		panic("failed to start server")
	}
}

func handler(w http.ResponseWriter, req *http.Request) {
	_, _ = fmt.Fprintf(w, "hello")
}