a thing to watch memory usage

watcher.go

package main

import (
        "fmt"
        "os"
        "runtime"
        "runtime/pprof"
        "time"
)

func Watch(threshold uint64, maxFreq time.Duration, cb func()) {
        var lastNotif time.Time
        for range time.Tick(time.Second) {
                var mstats runtime.MemStats
                runtime.ReadMemStats(&mstats)
                if mstats.Alloc > threshold && time.Since(lastNotif) > maxFreq {
                        cb()
                        lastNotif = time.Now()
                }
        }
}

func main() {
        go Watch(1<<30, time.Second*60*5, func() {
                fmt.Println("memory threshold triggered! writing profile!")
                fi, err := os.Create(fmt.Sprintf("high-mem-profile-%d", time.Now().UnixNano()))
                if err != nil {
                        fmt.Println("Error: failed to open file for memory profile: ", err)
                        return
                }
                defer fi.Close()
                if err := pprof.WriteHeapProfile(fi); err != nil {
                        fmt.Println("failed to write memory profile: ", err)
                }
        })

        var stuff [][]byte
        for range time.Tick(time.Millisecond) {
                stuff = append(stuff, make([]byte, 500000))
        }
}