fatal error: concurrent map writes

[qiukeren]

fatal error: concurrent map writes

goroutine 53 [running]:
runtime.throw(0x21d9a37, 0x15)
        /usr/local/go/src/runtime/panic.go:1117 +0x72 fp=0xc00059a5a8 sp=0xc00059a578 pc=0x56b952
runtime.mapdelete(0x204f0a0, 0xc00032e180, 0xc00059a638)
        /usr/local/go/src/runtime/map.go:702 +0x46e fp=0xc00059a608 sp=0xc00059a5a8 pc=0x544c6e
github.com/zekroTJA/timedmap.(*TimedMap).expireElement(0xc000618040, 0x2000940, 0xc007e1d690, 0x0, 0xc006694300)
        /root/go/pkg/mod/github.com/zekro!t!j!a/[email protected]/timedmap.go:177 +0xc5 fp=0xc00059a660 sp=0xc00059a608 pc=0x10756e5
github.com/zekroTJA/timedmap.(*TimedMap).cleanUp(0xc000618040)
        /root/go/pkg/mod/github.com/zekro!t!j!a/[email protected]/timedmap.go:190 +0x1a9 fp=0xc00059a758 sp=0xc00059a660 pc=0x10758a9
github.com/zekroTJA/timedmap.New.func1(0xc0000cc3c0, 0xc000618040)
        /root/go/pkg/mod/github.com/zekro!t!j!a/[email protected]/timedmap.go:62 +0x97 fp=0xc00059a7d0 sp=0xc00059a758 pc=0x1075f77
runtime.goexit()
        /usr/local/go/src/runtime/asm_amd64.s:1371 +0x1 fp=0xc00059a7d8 sp=0xc00059a7d0 pc=0x5a1ce1
created by github.com/zekroTJA/timedmap.New
        /root/go/pkg/mod/github.com/zekro!t!j!a/[email protected]/timedmap.go:58 +0xc5

[qiukeren]

离谱的是 我自己跑bench跑不出来这个结果

it is confusing i can't provide it with main.

package main

import (
	"github.com/remeh/sizedwaitgroup"
	"github.com/zekroTJA/timedmap"
	"math/rand"
	"time"
)

func main() {
	tm := timedmap.New(5 * time.Millisecond)
	rand.Seed(time.Now().UnixNano())

	swg := sizedwaitgroup.New(80)
	for i := 0; i < 5000000000; i++ {
		swg.Add()
		go func(i int) {
			defer swg.Done()
			//k := RandStringRunes(10)
			k := "a"
			tm.Set(k, rand.Int31(), 3*time.Millisecond)
		}(i)
	}
	swg.Wait()
}

[zekroTJA]

Well, that's actually an issue when writing to the map while concurrently reading an existing but expired value, which then would be removed from the map on getting it. The call to expireElement() is not protected by a RWLock, so the concurrent map write panic occurs.

I was actually able to reproduce the behavior in the following test:

timedmap/timedmap_test.go

Lines 279 to 298 in d533e81

	func TestGetExpiredConcurrent(t *testing.T) {
	tm := New(dCleanupTick)
	wg := sync.WaitGroup{}
	for i := 0; i < 50000; i++ {
	wg.Add(1)
	go func() {
	defer wg.Done()
	tm.Set(1, 1, 0)
	}()
	wg.Add(1)
	go func() {
	defer wg.Done()
	tm.GetValue(1)
	}()
	}
	wg.Wait()
	}

Result:
https://github.com/zekroTJA/timedmap/runs/2065005503?check_suite_focus=true#step:5:53

Now, it should be fixed with this change: e8e3b1e.

Thank you for the issue. ^^