Avoid crashing when "git annex get" fails to download from one location,
and falls back to downloading from a second location.
The problem is that git annex get calls download recursively from within
itself if the first download attempt fails. So the first time through, it
writes a transfer info file, which is then overwritten on the second,
recursive call. Then on cleanup, it tries to delete the file twice, which
of course doesn't work.
Fixed both by not crashing if the transfer file is removed, and by
changing Get to not run download recursively like that. It's the only
thing that did so, and it just seems like a bad idea.
This *almost* works.
Along the way, I noticed that the --uuid parameter was being accidentially
passed after the --, so that has never been actually used by
git-annex-shell to verify it's running in the expected repository. Oops. Fixed.
Not yet tested and places git-annex-shell is run need to be modified to
pass the new field settings.
Note that rsyncServerSend was changed to fork, rather than directly exec
rsync, because it needs to keep the transfer lock held, and clean up the
transfer log when done.
In order to record a semi-useful filename associated with the key,
this required plumbing the filename all the way through to the remotes'
storeKey and retrieveKeyFile.
Note that there is potential for deadlock here, narrowly avoided.
Suppose the repos are A and B. A sends file foo to B, and at the same
time, B gets file foo from A. So, A locks its upload transfer info file,
and then locks B's download transfer info file. At the same time,
B is taking the two locks in the opposite order. This is only not a
deadlock because the lock code does not wait, and aborts. So one of A or
B's transfers will be aborted and the other transfer will continue.
Whew!
Note this is per-remote, so trying to get the same file from multiple
remotes can still let duplicate downloads run. (And uploading the same file
to multiple remotes is not duplicate at all of course.)
get, move, and copy are the only git-annex subcommands that transfer
files, but there's still git-annex-shell recvkey and sendkey to deal with too.
I considered modifying retrieveKeyFile or getViaTmp, but they are called
by other code that does not involve expensive file transfers (migrate)
or that does file transfers that should not be checked by this (fsck --from).
While this word may be less familiar to some users, it avoids the
connotation that version 2 is better than version 1, which is wrong
when the two variants were conflicting.
Kqueue needs to remember which files failed to be added due to being open,
and retry them. This commit gets the data in place for such a retry thread.
Broke KeySource out into its own file, and added Eq and Ord instances
so it can be stored in a Set.
Was decoding the git-cat-file of the symlink target as utf8, but that can't
do, unix filenames are from the 70's and need this shiny disco
fileSystemEncoding.
Now it starts really, really fast! Down from 15 minutes or so on my big
tree to around 1 minute.
The trick is to remember the last time the daemon was running. Links with a
ctime from before that point don't need to be restaged on startup (as long
as they are correct), since the old daemon would have handled them already.
We also assume that if the daemon has never run before, any links that
already exist are good. The pre-commit hook fixes links, so this should be
a safe assumption.
Adds another MVar holding a DaemonStatus data structure. Also
allowed getting rid of the Annex.Fast hack. This data structure will
probably grow a lot of details about the daemon's status, that will
later be used by the webapp's UI.
The code to actually track when the daemon was last running is not written
yet. It's 3 am.
The idea, not yet done, is to use this to detect when a file
has an old change time, and avoid expensive restaging of the file.
If git-annex watch keeps track of the last time it finished a full scan,
then any symlink that is older than that time must have been scanned
before, so need not be added. (Relying on moving, copying, etc of a file
all updating its change time.)
Anyway, this info is available for free since inotify already checks it,
so it might as well make it available.
Now really only done in the startup scan.
It turns out to be quite hard for event handlers to know when the startup
scan is complete. I tried to make addWatch pass that info, but found
threading the state very difficult. For now, a quick hack, using the fast
flag.
Note that it's actually possible for inotify events to come in while the
startup scan is still ongoing. Due to my hack, the expensive check will
be done for files added in such inotify events.
This requires a relatively expensive test at file add time to see if it's
in git already. But it can be optimised to only happen during the startup
scan.
I thought this might be a lock conflict that explains the deadlock when
built with -threaded, but it seems not.. it still locks! It even locks
without the committer thread.
Indeed, it locks when running "git annex add"! -threaded is exposing some
other problem.
Still, this seems conceptually cleaner and did not add any inneficiencies.
Also added some high-level documentation about the threads used.
