This makes a couple of small improvements to the folder summary
mechanism:
- The folder summary includes the local and remote sequence numbers in
clear text, rather than some odd sum that I'm not sure what it was
intended to represent.
- The folder summary event is generated when appropriate, regardless of
whether there is an event listener. We did this before because
generating it was expensive, and we wanted to avoid doing it
unnecessarily. Nowadays, however, it's mostly just reading out
pre-calculated metadata, and anyway, it's nice if it shows up reliably
when running with -verbose.
The point of all this is to make it easier to use these events to judge
when devices are, in fact, in sync. As-is, if I'm looking at two
devices, it's very difficult to reliably determine if they are in sync
or not. The reason is that while we can ask device A if it thinks it's
in sync, we can't see if the answer is "yes" because it has processed
all changes from B, or if it just doesn't know about the changes from B
yet. With proper sequence numbers in the event we can compare the two
and determine the truth. This makes testing a lot easier.
Group the global list of files by version, instead of having one flat list for all devices. This removes lots of duplicate protocol.Vectors.
Co-authored-by: Jakob Borg <jakob@kastelo.net>
If we decide to recalculate the metadata we shouldn't start from
whatever we loaded from the database, as that data is wrong. We should
start from a clean slate.
This adds metadata updates to the same write batch as the underlying
file change. The odds of a metadata update going missing is greatly
reduced.
Bonus change: actually commit the transaction in recalcMeta.
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 PR does two things, because one lead to the other:
- Move the leveldb specific stuff into a small "backend" package that
defines a backend interface and the leveldb implementation. This allows,
potentially, in the future, switching the db implementation so another
KV store should we wish to do so.
- Add proper error handling all along the way. The db and backend
packages are now errcheck clean. However, I drew the line at modifying
the FileSet API in order to keep this manageable and not continue
refactoring all of the rest of Syncthing. As such, the FileSet methods
still panic on database errors, except for the "database is closed"
error which is instead handled by silently returning as quickly as
possible, with the assumption that we're anyway "on the way out".
To do so the BlockMap struct has been removed. It behaves like any other prefixed
part of the database, but was not integrated in the recent keyer refactor. Now
the database is only flushed when files are in a consistent state.
There was a problem in iterating the sequence index that could result
in missing updates. The issue is that while the index was (correctly)
iterated in a snapshot, the actual file infos were read dirty outside of
the snapshot. This fixes this by doing the reads inside the snapshot,
and also updates a couple of other places that did the same thing more
or less harmfully (I didn't investigate).
To avoid similar issues in the future I did some renaming of the
getFile* methods - the ones in a transaction are just getFile, while the
ones directly on the database are variants of getFileDirty to highlight
what's going on.
This adds a thin type that holds the state associated with the
leveldb.DB, leaving the huge Instance type more or less stateless. Also
moves some keying stuff into the DB package so that other packages need
not know the keying specifics.
(This does not, yet, fix the cmd/stindex program, in order to keep the
diff size down. Hence the keying constants are still exported.)
The problem here is that we would update the sequence index before
updating the FileInfos, which would result in a high sequence number
pointing to a low-sequence FileInfo. The index sender would pick up the
high sequence number, send the old file, and think everything was good.
On the receiving side the old file is a no-op and ignored. The file
remains out of sync until another update for it happens.
This fixes that by correcting the order of operations in the database
update: first we remove old sequence index entries, then we update the
FileInfos (which now don't have anything pointing to them) and then we
add the sequence indexes (which the index sender can see).
The other option is to add "proper" transactions where required at the
database layer. I actually have a branch for that, but it's literally
thousands of lines of diff and I'm putting that off for another day as
this solves the problem...
