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lib/db: Recover sequence number and metadata on startup (fixes #6335) (#6336)

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lib/db: Recover sequence number and metadata on startup (fixes #6335)

If we crashed after writing new file entries but before updating
metadata in the database the sequence number and metadata will be wrong.
This fixes that.
This commit is contained in:
Jakob Borg 2020-02-13 13:05:26 +01:00 committed by GitHub
parent d95a087829
commit 51fa36d61f
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 47 additions and 13 deletions
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60
lib/db/set.go
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@ -71,7 +71,7 @@ func init() {
}
func NewFileSet(folder string, fs fs.Filesystem, db *Lowlevel) *FileSet {
var s = FileSet{
var s = &FileSet{
folder: folder,
fs: fs,
db: db,
@ -79,26 +79,34 @@ func NewFileSet(folder string, fs fs.Filesystem, db *Lowlevel) *FileSet {
updateMutex: sync.NewMutex(),
}
if err := s.meta.fromDB(db, []byte(folder)); err != nil {
l.Infof("No stored folder metadata for %q: recalculating", folder)
if err := s.recalcCounts(); backend.IsClosed(err) {
return nil
} else if err != nil {
panic(err)
}
} else if age := time.Since(s.meta.Created()); age > databaseRecheckInterval {
l.Infof("Stored folder metadata for %q is %v old; recalculating", folder, age)
if err := s.recalcCounts(); backend.IsClosed(err) {
recalc := func() *FileSet {
if err := s.recalcMeta(); backend.IsClosed(err) {
return nil
} else if err != nil {
panic(err)
}
return s
}
return &s
if err := s.meta.fromDB(db, []byte(folder)); err != nil {
l.Infof("No stored folder metadata for %q; recalculating", folder)
return recalc()
}
if metaOK := s.verifyLocalSequence(); !metaOK {
l.Infof("Stored folder metadata for %q is out of date after crash; recalculating", folder)
return recalc()
}
if age := time.Since(s.meta.Created()); age > databaseRecheckInterval {
l.Infof("Stored folder metadata for %q is %v old; recalculating", folder, age)
return recalc()
}
return s
}
func (s *FileSet) recalcCounts() error {
func (s *FileSet) recalcMeta() error {
s.meta = newMetadataTracker()
if err := s.db.checkGlobals([]byte(s.folder), s.meta); err != nil {
@ -123,6 +131,32 @@ func (s *FileSet) recalcCounts() error {
return s.meta.toDB(s.db, []byte(s.folder))
}
// Verify the local sequence number from actual sequence entries. Returns
// true if it was all good, or false if a fixup was necessary.
func (s *FileSet) verifyLocalSequence() bool {
// Walk the sequence index from the current (supposedly) highest
// sequence number and raise the alarm if we get anything. This recovers
// from the occasion where we have written sequence entries to disk but
// not yet written new metadata to disk.
//
// Note that we can have the same thing happen for remote devices but
// there it's not a problem -- we'll simply advertise a lower sequence
// number than we've actually seen and receive some duplicate updates
// and then be in sync again.
curSeq := s.meta.Sequence(protocol.LocalDeviceID)
snap := s.Snapshot()
ok := true
snap.WithHaveSequence(curSeq+1, func(fi FileIntf) bool {
ok = false // we got something, which we should not have
return false
})
snap.Release()
return ok
}
func (s *FileSet) Drop(device protocol.DeviceID) {
l.Debugf("%s Drop(%v)", s.folder, device)