This doesn't avoid it sometimes attempting to commit when there are no
changes. Typically that happens when a change is pushed in from another
repo; the watcher sees the file and tries to stage it, resulting in an
empty commit. Really fixing that would probably use more CPU than
occasionally trying to make an empty commit.
However, this does save a lot of unnecessary work, as those empty commits
had to be synced out, which no longer happens.
This ensures file propigate takes place in situations such as: Usb drive A
is connected to B. A's master branch is already in sync with B, but it is
being used to sneakernet some files around, so B downloads those. There is no
master branch change, so C does not request these files. B needs to upload
the files it just downloaded on to C, etc.
My first try at this, I saw loops happen. B uploaded to C, which then
tried to upload back to B (because it had not received the updated
git-annex branch from B yet). B already had the file, but it still created
a transfer info file from the incoming transfer, and its watcher saw
that be removed, and tried to upload back to C.
These loops should have been fixed by my previous commit. (They never
affected ssh remotes, only local ones, it seemed.) While C might still try
to upload to B, or to some other remote that already has the file, the
extra work dies out there.
I was seeing some interesting crashes after the previous commit,
when making file changes slightly faster than the assistant could keep up.
error: Ref refs/heads/master is at 7074f8e0a11110c532d06746e334f2fec6af6ab4 but expected 95ea86008d72a40d97a81cfc8fb47a0da92166bd
fatal: cannot lock HEAD ref
Committer crashed: git commit [Param "--allow-empty-message",Param "-m",Param "",Param "--allow-empty",Param "--quiet"] failed
Pusher crashed: thread blocked indefinitely in an STM transaction
Clearly the the merger ended up running at the same time as the committer,
and with both modifying HEAD the committer crashed. I fixed that by
making the Merger run its merge inside the annex monad, which avoids
it running concurrently with other git operations. Also by making
the committer not crash if git fails.
What I don't understand is why the pusher then crashed with a STM deadlock.
That must be in either the DaemonStatusHandle or the FailedPushMap,
and the latter is only used by the pusher. Did the committer's crash somehow
break STM?
The BlockedIndefinitelyOnSTM exception is described as:
-- |The thread is waiting to retry an STM transaction, but there are no
-- other references to any @TVar@s involved, so it can't ever continue.
If the Committer had a reference to a TVar and crashed, I can sort of see
this leading to that exception..
The crash was quite easy to reproduce after the previous commit, but
after making the above change, I have yet to see it again. Here's hoping.
Now when a download is queued and there's no known remote to get it from,
it's added to a deferred download list, which will be retried later.
The Merger thread tries to queue any deferred downloads when it receives
a push to the git-annex branch.
Note that the Merger thread now also forces an update of the git-annex
branch. The assistant was not updating this branch before, and it saw a
(mostly) correct view of state, but now that incoming pushes go to
synced/git-annex, it needs to be merged in.
Don't expose these as branches in refs/heads/. Instead hide them away in
refs/synced/ where only show-ref will find them.
Make unused only look at branches and tags, not these other things,
so it won't care if some stale sync ref used to use a file.
This means they don't need to be deleted, which could have
led to an incoming sync being missed.
The fallback branches pushed to contain the uuid of the pusher, which is
ugly. That's why syncing doesn't normally use this method.
The merger deletes fallback branches after merging them, to contain the
ugliness, and so unused doesn't look at data from these branches.
(The fallback git-annex branch is left behind for now.)
Finally.
Last bug fixes here: Send PairResp with same UUID in the PairReq.
Fix off-by-one in code that filters out our own pairing messages.
Also reworked the pairing alerts, which are still slightly buggy.
Pair requests the the same UUID are part of the same pairing session,
which allows us to detect attempts to brute force the shared secret,
as that will result in pair requests with the same UUID that are
not verified with the right secret.
They work fine. But I had to go to a lot of trouble to get Yesod to render
routes in a pure function. It may instead make more sense to have each
alert have an assocated IO action, and a single route that runs the IO
action of a given alert id. I just wish I'd realized that before the past
several hours of struggling with something Yesod really doesn't want to
allow.
Avoid trying to git push/pull to special remotes, but still do transfer
scans of them, after git pull from any other remotes, so we know about
any values that have been placed on them.
When multiple downloads of a key are queued, it starts the first, but leaves the
other downloads in the queue. This ensures that we don't lose a queued
download if the one that got started failed.
Run code that pops off the next queued transfer and adds it to the active
transfer map within an allocated transfer slot, rather than before
allocating a slot. Fixes the transfers display, which had been displaying
the next transfer as a running transfer, while the previous transfer was
still running.
Currently only the web special remote is readonly, but it'd be possible to
also have readonly drives, or other remotes. These are handled in the
assistant by only downloading from them, and never trying to upload to
them.
The expensive transfer scan now scans a whole set of remotes in one pass.
So at startup, or when network comes up, it will run only once.
Note that this can result in transfers from/to higher cost remotes being
queued before other transfers of other content from/to lower cost remotes.
Before, low cost remotes were scanned first and all their transfers came
first. When multiple transfers are queued for a key, the lower cost ones
are still queued first. However, this could result in transfers from slow
remotes running for a long time while transfers of other data from faster
remotes waits.
I expect to make the transfer queue smarter about ordering
and/or make it allow multiple transfers at a time, which should eliminate
this annoyance. (Also, it was already possible to get into that situation,
for example if the network was up, lots of transfers from slow remotes
might be queued, and then a disk is mounted and its faster transfers have
to wait.)
Also note that this means I don't need to improve the code in
Assistant.Sync that currently checks if any of the reconnected remotes
have diverged, and if so, queues scans of all of them. That had been very
innefficient, but now doesn't matter.
Used by the assistant, rather than copy, this is faster because it avoids
using git ls-files, avoids checking the location log redundantly, and
runs in oneshot mode, avoiding making a commit to the git-annex branch
for every file transferred.
There are multiple reasons to do this:
* The local network may be up solid, but a route to a networked remote
is having trouble. Any transfers to it that fail should be retried.
* Someone might have wicd running, but like to bring up new networks
by hand too. This way, it'll eventually notice them.
The problem with using it here is that, if a removable drive is scanned
and gets disconnected during the scan, testing for all the files will
indicate it doesn't have them, and the scan is logged as completed
successfully, without necessary transfers being queued.
This deals with interruptions in network connectevity, by listening
for a new network interface coming up (using dbus to see when
network-manager or wicd do it), and forcing a rescan of
This seems to work pretty well.
Handled the process groups like this:
- git-annex processes started by the assistant for transfers are run in their
own process groups.
- otherwise, rely on the shell to allocate a process group for git-annex
There is potentially a problem if some other program runs git-annex
directly (not using sh -c) The program and git-annex would then be in
the same process group. If that git-annex starts a transfer and it's
canceled, the program would also get killed. May or may not be a desired
result.
Also, the new updateTransferInfo probably closes a race where it was
possible for the thread id to not be recorded in the transfer info, if
the transfer info file from the transfer process is read first.
This doesn't quite work, because canceling a transfer sends a signal
to git-annex, but not to rsync (etc).
Looked at making git-annex run in its own process group, which could then
be killed, and would kill child processes. But, rsync checks if it's
process group is the foreground process group and doesn't show progress if
not, and when git has run git-annex, if git-annex makes a new process
group, that is not the case. Also, if git has run git-annex, ctrl-c
wouldn't be propigated to it if it made a new process group.
So this seems like a blind alley, but recording it here just in case.
Now an alert tracks files that have recently been added. As a large file
is added, it will have its own alert, that then combines with the tracker
when dones.
Also used for combining sanity checker alerts, as it could possibly want to
display a lot.
This allows me to not build-depend on blaze-markup, which was causing
me some trouble when tring to build with cabal on debian. Seems debian
ships Text.Blaze.Renderer.String in two packages.
Now the javascript does an ajax call at the start to request the url
to use to poll, and the notification id is generated then, once we know
javascript is working.
Depending on how the webapp was started up and whether the user clicked on
any links in it, window.close() may be disallowed by browser security
policy. Also if that fails, display a modal dialog that nicely blackens out
the webapp.
TODO: avoid Escape closing it. Bootstrap's docs are unclear about how to do
that.
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.
