git-annex/Assistant/Threads/TransferWatcher.hs
Joey Hess a76078a78e process group killing
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.
2012-08-10 15:52:22 -04:00

75 lines
2.2 KiB
Haskell

{- git-annex assistant transfer watching thread
-
- Copyright 2012 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Assistant.Threads.TransferWatcher where
import Assistant.Common
import Assistant.ThreadedMonad
import Assistant.DaemonStatus
import Logs.Transfer
import Utility.DirWatcher
import Utility.Types.DirWatcher
thisThread :: ThreadName
thisThread = "TransferWatcher"
{- This thread watches for changes to the gitAnnexTransferDir,
- and updates the DaemonStatus's map of ongoing transfers. -}
transferWatcherThread :: ThreadState -> DaemonStatusHandle -> IO ()
transferWatcherThread st dstatus = do
g <- runThreadState st $ fromRepo id
let dir = gitAnnexTransferDir g
createDirectoryIfMissing True dir
let hook a = Just $ runHandler st dstatus a
let hooks = mkWatchHooks
{ addHook = hook onAdd
, delHook = hook onDel
, errHook = hook onErr
}
void $ watchDir dir (const False) hooks id
debug thisThread ["watching for transfers"]
type Handler = ThreadState -> DaemonStatusHandle -> FilePath -> Maybe FileStatus -> IO ()
{- Runs an action handler.
-
- Exceptions are ignored, otherwise a whole thread could be crashed.
-}
runHandler :: ThreadState -> DaemonStatusHandle -> Handler -> FilePath -> Maybe FileStatus -> IO ()
runHandler st dstatus handler file filestatus = void $ do
either print (const noop) =<< tryIO go
where
go = handler st dstatus file filestatus
{- Called when there's an error with inotify. -}
onErr :: Handler
onErr _ _ msg _ = error msg
{- Called when a new transfer information file is written. -}
onAdd :: Handler
onAdd st dstatus file _ = case parseTransferFile file of
Nothing -> noop
Just t -> go t =<< runThreadState st (checkTransfer t)
where
go _ Nothing = noop -- transfer already finished
go t (Just info) = do
debug thisThread
[ "transfer starting:"
, show t
]
updateTransferInfo dstatus t info
{- Called when a transfer information file is removed. -}
onDel :: Handler
onDel _ dstatus file _ = case parseTransferFile file of
Nothing -> noop
Just t -> do
debug thisThread
[ "transfer finishing:"
, show t
]
void $ removeTransfer dstatus t