WriteBatch.Flush panics if called twice

Issues
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1

Moved from GitHub badger/1394

Posted by mvdan:

I understand that flushing twice doesn’t make sense, since a batch can only be flushed once, but the second call should error with a helpful message instead of panicking.

$ go version
go version devel +152ffca82f Mon Jun 29 08:06:32 2020 +0000 linux/amd64
$ go list -m github.com/dgraph-io/badger/v2
github.com/dgraph-io/badger/v2 v2.0.3
$ cat main.go
package main

import (
	"io/ioutil"
	"os"

	"github.com/dgraph-io/badger/v2"
)

func main() {
	dir, err := ioutil.TempDir("", "badger-test")
	if err != nil {
		panic(err)
	}
	defer os.RemoveAll(dir)
	db, err := badger.Open(badger.DefaultOptions(dir))
	if err != nil {
		panic(err)
	}
	defer db.Close()

	wb := db.NewWriteBatch()
	wb.Flush()
	wb.Flush()
}
$ go run main.go
badger 2020/06/30 18:36:15 INFO: All 0 tables opened in 0s
badger 2020/06/30 18:36:15 INFO: Got compaction priority: {level:0 score:1.73 dropPrefix:[]}
panic: send on closed channel

goroutine 1 [running]:
github.com/dgraph-io/badger/v2/y.(*Throttle).Do(0xc0000200c0, 0x6e7260, 0xc0000200c0)
	/home/mvdan/go/pkg/mod/github.com/dgraph-io/badger/v2@v2.0.3/y/y.go:260 +0xc9
github.com/dgraph-io/badger/v2.(*WriteBatch).commit(0xc000020180, 0x0, 0x0)
	/home/mvdan/go/pkg/mod/github.com/dgraph-io/badger/v2@v2.0.3/batch.go:141 +0x45
github.com/dgraph-io/badger/v2.(*WriteBatch).Flush(0xc000020180, 0x0, 0x0)
	/home/mvdan/go/pkg/mod/github.com/dgraph-io/badger/v2@v2.0.3/batch.go:155 +0x45
main.main()
	/home/mvdan/src/test/main.go:24 +0x1fa
exit status 2
2

mvdan commented :

Flush after Cancel similarly panics.

3

@mvdan PR for Fix: Throttle.Do does not panic after Finish by ekalinin · Pull Request #1396 · dgraph-io/badger · GitHub

4

Oh. I would have noticed and likely reviewed the change if an issue tracker was actually used for bugs. The forum doesn’t integrate at all with PRs, and I’m entirely too late now.

5

Understood. Going forward we can post our PRs before they are merged. I will communicate that with the team. thanks for bringing this up. Please PM me directly if you want to reopen the issue. I am closing it for now.

1 Like