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|
{- git-annex assistant daemon
-
- Copyright 2012 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-
- Overview of threads and MVars, etc:
-
- Thread 1: parent
- The initial thread run, double forks to background, starts other
- threads, and then stops, waiting for them to terminate,
- or for a ctrl-c.
- Thread 2: watcher
- Notices new files, and calls handlers for events, queuing changes.
- Thread 3: inotify internal
- Used by haskell inotify library to ensure inotify event buffer is
- kept drained.
- Thread 4: inotify startup scanner
- Scans the tree and registers inotify watches for each directory.
- A MVar lock is used to prevent other inotify handlers from running
- until this is complete.
- Thread 5: committer
- Waits for changes to occur, and runs the git queue to update its
- index, then commits.
- Thread 6: status logger
- Wakes up periodically and records the daemon's status to disk.
- Thread 7: sanity checker
- Wakes up periodically (rarely) and does sanity checks.
-
- ThreadState: (MVar)
- The Annex state is stored here, which allows resuscitating the
- Annex monad in IO actions run by the inotify and committer
- threads. Thus, a single state is shared amoung the threads, and
- only one at a time can access it.
- DaemonStatusHandle: (MVar)
- The daemon's current status. This MVar should only be manipulated
- from inside the Annex monad, which ensures it's accessed only
- after the ThreadState MVar.
- ChangeChan: (STM TChan)
- Changes are indicated by writing to this channel. The committer
- reads from it.
-}
module Assistant where
import Common.Annex
import Assistant.ThreadedMonad
import Assistant.DaemonStatus
import Assistant.Changes
import Assistant.Watcher
import Assistant.Committer
import Assistant.SanityChecker
import qualified Utility.Daemon
import Utility.LogFile
import Control.Concurrent
startDaemon :: Bool -> Annex ()
startDaemon foreground
| foreground = do
showStart "watch" "."
go id
| otherwise = do
logfd <- liftIO . openLog =<< fromRepo gitAnnexLogFile
pidfile <- fromRepo gitAnnexPidFile
go $ Utility.Daemon.daemonize logfd (Just pidfile) False
where
go a = withThreadState $ \st -> do
checkCanWatch
dstatus <- startDaemonStatus
liftIO $ a $ do
changechan <- newChangeChan
-- The commit thread is started early,
-- so that the user can immediately
-- begin adding files and having them
-- committed, even while the startup scan
-- is taking place.
_ <- forkIO $ commitThread st changechan
_ <- forkIO $ daemonStatusThread st dstatus
_ <- forkIO $ sanityCheckerThread st dstatus changechan
-- Does not return.
watchThread st dstatus changechan
stopDaemon :: Annex ()
stopDaemon = liftIO . Utility.Daemon.stopDaemon =<< fromRepo gitAnnexPidFile
|
