bug: options for storage and log streams can be messed up

[ijsong]

LogStreamReplicas are initiated concurrently, like below.

varlog/internal/storagenode/storagenode.go

Lines 151 to 154 in 6f36b0d

	g.Go(func() error {
	_, err := sn.runLogStreamReplica(context.Background(), dataDir.TopicID, dataDir.LogStreamID, dataDir.String())
	return err
	})

When creating storage, default options that belong to the storage node are reused. However, it can be buggy when reusing a slice in different goroutines.

varlog/internal/storagenode/storagenode.go

Lines 309 to 313 in 6f36b0d

	stg, err := storage.New(append(
	sn.defaultStorageOptions,
	storage.WithPath(lsPath),
	storage.WithLogger(sn.logger.Named("storage").With(zap.String("path", lsPath))),
	)...)

Here is a simple reproducible code:

var common []int

func init() {
	common = make([]int, 0, 5)
	common = append(common, 1)
	common = append(common, 2)
}

func main() {
	var wg sync.WaitGroup
	wg.Add(2)
	go func() {
		defer wg.Done()
		fmt.Printf("%+v", append(common, 11, 12))
	}()
	go func() {
		defer wg.Done()
		fmt.Printf("%+v", append(common, 21, 22))
	}()
	wg.Wait()
}

// [1 2 11 12][1 2 11 12]