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Deal with zero-length segments

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Signed-off-by: Fabian Reinartz <freinartz@google.com>
This commit is contained in:
Fabian Reinartz 2018-06-05 04:50:20 -04:00
parent 92e1b20957
commit 22fd3ef24e
3 changed files with 28 additions and 6 deletions
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2
repair_test.go
View file

@ -76,7 +76,7 @@ func TestRepairBadIndexVersion(t *testing.T) {
} }
// On DB opening all blocks in the base dir should be repaired. // On DB opening all blocks in the base dir should be repaired.
db, _ := Open("testdata/repair_index_version", nil, nil, nil) db, err := Open("testdata/repair_index_version", nil, nil, nil)
if err != nil { if err != nil {
t.Fatal(err) t.Fatal(err)
} }

15
wal.go
View file

@ -1214,6 +1214,9 @@ func (r *walReader) decodeDeletes(flag byte, b []byte, res *[]Stone) error {
// MigrateWAL rewrites the deprecated write ahead log into the new format. // MigrateWAL rewrites the deprecated write ahead log into the new format.
func MigrateWAL(logger log.Logger, dir string) (err error) { func MigrateWAL(logger log.Logger, dir string) (err error) {
if logger == nil {
logger = log.NewNopLogger()
}
// Detect whether we still have the old WAL. // Detect whether we still have the old WAL.
fns, err := sequenceFiles(dir) fns, err := sequenceFiles(dir)
if err != nil && !os.IsNotExist(err) { if err != nil && !os.IsNotExist(err) {
@ -1222,7 +1225,8 @@ func MigrateWAL(logger log.Logger, dir string) (err error) {
if len(fns) == 0 { if len(fns) == 0 {
return nil // No WAL at all yet. return nil // No WAL at all yet.
} }
// Check header of first segment. // Check header of first segment to see whether we are still dealing with an
// old WAL.
f, err := os.Open(fns[0]) f, err := os.Open(fns[0])
if err != nil { if err != nil {
return errors.Wrap(err, "check first existing segment") return errors.Wrap(err, "check first existing segment")
@ -1230,13 +1234,14 @@ func MigrateWAL(logger log.Logger, dir string) (err error) {
defer f.Close() defer f.Close()
var hdr [4]byte var hdr [4]byte
if n, err := f.Read(hdr[:]); err != nil { if _, err := f.Read(hdr[:]); err != nil && err != io.EOF {
return errors.Wrap(err, "read header from first segment") return errors.Wrap(err, "read header from first segment")
} else if n != 4 {
return errors.New("could not read full header from segment")
} }
// If we cannot read the magic header for segments of the old WAL, abort.
// Either it's migrated already or there's a corruption issue with which
// we cannot deal here anyway. Subsequent attempts to open the WAL will error in that case.
if binary.BigEndian.Uint32(hdr[:]) != WALMagic { if binary.BigEndian.Uint32(hdr[:]) != WALMagic {
return nil // Not the old WAL anymore. return nil
} }
level.Info(logger).Log("msg", "migrating WAL format") level.Info(logger).Log("msg", "migrating WAL format")

17
wal_test.go
View file

@ -434,6 +434,23 @@ func TestWALRestoreCorrupted(t *testing.T) {
} }
} }
func TestMigrateWAL_Empty(t *testing.T) {
// The migration proecedure must properly deal with a zero-length segment,
// which is valid in the new format.
dir, err := ioutil.TempDir("", "walmigrate")
testutil.Ok(t, err)
defer os.RemoveAll(dir)
wdir := path.Join(dir, "wal")
// Initialize empty WAL.
w, err := wal.New(nil, nil, wdir)
testutil.Ok(t, err)
testutil.Ok(t, w.Close())
testutil.Ok(t, MigrateWAL(nil, wdir))
}
func TestMigrateWAL_Fuzz(t *testing.T) { func TestMigrateWAL_Fuzz(t *testing.T) {
dir, err := ioutil.TempDir("", "walmigrate") dir, err := ioutil.TempDir("", "walmigrate")
testutil.Ok(t, err) testutil.Ok(t, err)