func Exist(dirpath string) bool {
names, err := fileutil.ReadDir(dirpath)
if err != nil {
return false
}
return len(names) != 0
}
// openLast opens the last wal file for read and write.
func openLast(dirpath string) (*os.File, error) {
names, err := fileutil.ReadDir(dirpath)
if err != nil {
return nil, err
}
names = checkWalNames(names)
if len(names) == 0 {
return nil, ErrFileNotFound
}
last := path.Join(dirpath, names[len(names)-1])
return os.OpenFile(last, os.O_RDWR, 0)
}
func openAtIndex(dirpath string, snap walpb.Snapshot, write bool) (*WAL, error) {
names, err := fileutil.ReadDir(dirpath)
if err != nil {
return nil, err
}
names = checkWalNames(names)
if len(names) == 0 {
return nil, ErrFileNotFound
}
nameIndex, ok := searchIndex(names, snap.Index)
if !ok || !isValidSeq(names[nameIndex:]) {
return nil, ErrFileNotFound
}
// open the wal files for reading
rcs := make([]io.ReadCloser, 0)
ls := make([]fileutil.Lock, 0)
for _, name := range names[nameIndex:] {
f, err := os.Open(path.Join(dirpath, name))
if err != nil {
return nil, err
}
l, err := fileutil.NewLock(f.Name())
if err != nil {
return nil, err
}
err = l.TryLock()
if err != nil {
if write {
return nil, err
}
}
rcs = append(rcs, f)
ls = append(ls, l)
}
rc := MultiReadCloser(rcs...)
// create a WAL ready for reading
w := &WAL{
dir: dirpath,
start: snap,
decoder: newDecoder(rc),
locks: ls,
}
if write {
// open the lastest wal file for appending
seq, _, err := parseWalName(names[len(names)-1])
if err != nil {
rc.Close()
return nil, err
}
last := path.Join(dirpath, names[len(names)-1])
f, err := os.OpenFile(last, os.O_WRONLY|os.O_APPEND, 0)
if err != nil {
rc.Close()
return nil, err
}
err = fileutil.Preallocate(f, segmentSizeBytes)
if err != nil {
rc.Close()
plog.Errorf("failed to allocate space when creating new wal file (%v)", err)
return nil, err
}
w.f = f
w.seq = seq
}
return w, nil
}