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blog for the day

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Joey Hess 2012-06-21 01:07:37 -04:00
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... I'm getting tired of kqueue.
But the end of the tunnel is in sight. Today I made git-annex handle files
that are still open for write after a kqueue creation event is received.
Unlike with inotify, which has a new event each time a file is closed,
kqueue only gets one event when a file is first created, and so git-annex
needs to retry adding files until there are no writers left.
Eventually I found an elegant way to do that. The committer thread already
wakes up every second as long as there's a pending change to commit. So for
adds that need to be retried, it can just push them back onto the change
queue, and the committer thread will wait one second and retry the add. One
second might be too frequent to check, but it will do for now.
This means that `git annex watch` should now be usable on OSX, FreeBSD, and
NetBSD! (It'll also work on Debian kFreeBSD once [lsof is ported to it](http://bugs.debian.org/589103).)
I've meged kqueue support to `master`.
I also think I've squashed the empty commits that were sometimes made.
Incidentally, I'm 50% through my first month, and finishing [[inotify]]
was the first half of my roadmap for this month. Seem to be right on
schedule.. Now I need to start thinking about [[syncing]].

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@ -13,11 +13,6 @@ There is a `watch` branch in git that adds the command.
* When you `git annex unlock` a file, it will immediately be re-locked.
* With kqueue, if a file is created and still has a writer, it'll
give up adding it, and it will never get added. This is because kqueue
cannot track file closes. Need to go back and check these files every
second or something.
* Kqueue has to open every directory it watches, so too many directories
will run it out of the max number of open files (typically 1024), and fail.
I may need to fork off multiple watcher processes to handle this.