Putting the transfer on the currentTransfers atomically introduced a bug:
It checks to see if the transfer is in progress, and cancels it.
Fixed by moving that check inside the STM transaction.
This may be customised differently than the main page later on, but
for now the important thing is that this constantly refreshed page does not
allocate a new NotificationHandle each time it's loaded.
WebApp now shows changes with no delay. Comparing a running git-annex get
and the webapp side-by-side, they both show each new transfer at the same
time.
The fun part was making it move things from TransferQueue to currentTransfers
entirely atomically. Which will avoid inconsistent display if the WebApp
renders the current status at just the wrong time. STM to the rescue!
I've convinced myself that nothing in DaemonStatus can deadlock,
as it always keepts the TMVar full. That was the only reason it was in the
Annex monad.
This avoids forking another process, avoids polling, fixes a race,
and avoids a rare forkProcess thread hang that I saw once time
when starting the webapp.
Had to switch to toWaiAppPlain to avoid a seeming bug in toWaiApp;
chromium only received a partial copy of jquery. Always the same length
each time, which makes me think it's a bug in the compression, although
a bug in the autohead middleware is also a possibility.
Anyway, there's little need for compression for a local webapp. Not wasting
time compressing things is probably a net gain.
Similarly, I've not worried about minifying this yet. Although that would
avoid bloating the git-annex binary quite so much.
Very happy to have a reusable autoUpdate widget that can make any Yesod
widget automatically refresh!
Also added support for non-javascript browsers, falling back to meta
refresh.
Also, the home page is now rendered with the webapp status on it, before
any refreshing is done.
The webapp is now a constantly updating clock! I accomplished this amazing
feat using "long polling", with some jquery and a little custom java
script.
There are more modern techniques, but this one works everywhere.
Broke hamlet out into standalone files.
I don't like the favicon display; it should be served from /favicon.ico,
but I could only get the static site to serve /static/favicon.ico, so
I had to use a <link rel=icon> to pull it in. I looked at
Yesod.Default.Handlers.getFaviconR, but it doesn't seem to embed
the favicon into the binary?
Best dbus events I could find were setupDone from org.kde.Solid.Device.
There may be some spurious events, but that's ok, the code will only
check to see if new mounts are available.
It does not try to auto-start this service if it's not running.
This should fix OSX/BSD issues with not noticing transfer information
files with kqueue. Now that threads are used, the thread can manage the
transfer slot allocation and deallocation by itself; much cleaner.
Check first if a transfer needs to be done, using the location log only
(for speed), and avoid occupying a slot if not. Always write a transfer
info file, and keep it open throughout the tranfer process.
Now transfers to remotes seem reliable.
There's still a bug; if the child updates its transfer info file,
then the data from it will superscede the TransferInfo, losing the
info that we should wait on this child.
Added knownRemotes to DaemonStatus. This list is not entirely trivial to
calculate, and having it here should make it easier to add/remove remotes
on the fly later on. It did require plumbing the daemonstatus through to
some more threads.
The reason the DirWatcher had to wait for program termination was because
it used withINotify, so when it finished, its watcher threads were killed.
But since I have two DirWatcher threads now, that was not good, and could
perhaps explain the MVar problem I saw yesterday. In any case, fixed this
part of the code by making the DirWatcher return a handle that can be used
to stop it, and now the main Assistant thread is the only one calling
waitForTermination.
Avoid MVar deadlock issue, which I don't understand.
Have not taken the time to debug it fully, because it turns out I don't
need to resolve merge conflicts when a new branch ref is written... I
think.
Ensure the git-annex branch is merged when doing a manual pull.
Otherwise it can get out of sync, since git-annex normally only merges it
once per run.
SampleMVar won't work; between getting the current value and changing
it, another thread could made a change, which would get lost.
TMVar works well; this update situation is handled by atomic transactions.
Note that, since this always pushes branch synced/master to the remote, it
assumes that master has already gotten all the commits that are on the
remote merged in. Otherwise, fast-forward prevention may prevent the push.
That's probably ok, because the next stage is to automatically detect
incoming pushes and merge.
It's possible for there to be multiple queued changes all adding the same
file, and for those changes to be reordered. Maybe. This check will guard
against that ending up adding the wrong version of the file last.
Rethought how to keep track of pending adds that need to be retried later.
The commit thread already run up every second when there are changes,
so let's keep pending adds queued as changes until they're safe to add.
Also, the committer is now smarter about avoiding empty commits when
all the adds are currently unsafe, or in the rare case that an add event
for a symlink is not received in time. It may avoid them entirely.
This seems to work as before for inotify, and is untested for kqueue.
(Actually commit batching seems to be improved for inotify, although I'm
not sure why. I'm seeing only two commits made during large batch
operations, and the first of those is the non-batch mode commit.)
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.
There is indeed a race waiting for LinkChanges:
1. file annexed, link made
2. link deleted
3. inotify event for link creation runs, but as link is gone, handler is not run
Defer adding files to the annex until commit time, when during a batch
operation, a bundle of files will be available. This will allow for
checking a them all with a single lsof call.
The tricky part is that adding the file causes a symlink change inotify.
So I made it wait for an appropriate number of symlink changes to be
received before continuing with the commit. This avoids any delay
in the commit process. It is possible that some unrelated symlink change is
made; if that happens it'll commit it and delay committing the newly added
symlink for 1 second. This seems ok. I do rely on the expected symlink
change event always being received, but only when the add succeeds.
Another way to do it might be to directly stage the symlink, and then
ignore the redundant symlink change event. That would involve some
redundant work, and perhaps an empty commit, but if this code turns
out to have some bug, that'd be the best way to avoid it.
FWIW, this change seems to, as a bonus, have produced better grouping
of batch changes into single commits. Before, a large batch change would
result in a series of commits, with the first containing only one file,
and each of the rest bundling a number of files. Now, the added wait for
the symlink changes to arrive gives time for additional add changes to
be processed, all within the same commit.
A few places catch IO errors after calling runThreadState,
but since the MVar was not restored, it'd later deadlock trying to read
from it.
I'd like to catch all exceptions here, but I could not get the types
to unify.
