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|
{- git-annex assistant transfer slots
-
- Copyright 2012 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Assistant.TransferSlots where
import Assistant.Common
import Utility.ThreadScheduler
import Assistant.Types.TransferSlots
import Assistant.DaemonStatus
import Logs.Transfer
import qualified Control.Exception as E
import Control.Concurrent
import qualified Control.Concurrent.MSemN as MSemN
type TransferGenerator = Assistant (Maybe (Transfer, TransferInfo, Assistant ()))
{- Waits until a transfer slot becomes available, then runs a
- TransferGenerator, and then runs the transfer action in its own thread.
-}
inTransferSlot :: TransferGenerator -> Assistant ()
inTransferSlot gen = do
flip MSemN.wait 1 <<~ transferSlots
runTransferThread =<< gen
{- Runs a TransferGenerator, and its transfer action,
- without waiting for a slot to become available. -}
inImmediateTransferSlot :: TransferGenerator -> Assistant ()
inImmediateTransferSlot gen = do
flip MSemN.signal (-1) <<~ transferSlots
runTransferThread =<< gen
{- Runs a transfer action, in an already allocated transfer slot.
- Once it finishes, frees the transfer slot.
-
- Note that the action is subject to being killed when the transfer
- is canceled or paused.
-
- A PauseTransfer exception is handled by letting the action be killed,
- then pausing the thread until a ResumeTransfer exception is raised,
- then rerunning the action.
-}
runTransferThread :: Maybe (Transfer, TransferInfo, Assistant ()) -> Assistant ()
runTransferThread Nothing = flip MSemN.signal 1 <<~ transferSlots
runTransferThread (Just (t, info, a)) = do
d <- getAssistant id
aio <- asIO a
tid <- liftIO $ forkIO $ runTransferThread' d aio
updateTransferInfo t $ info { transferTid = Just tid }
runTransferThread' :: AssistantData -> IO () -> IO ()
runTransferThread' d a = go
where
go = catchPauseResume a
pause = catchPauseResume $ runEvery (Seconds 86400) noop
{- Note: This must use E.try, rather than E.catch.
- When E.catch is used, and has called go in its exception
- handler, Control.Concurrent.throwTo will block sometimes
- when signaling. Using E.try avoids the problem. -}
catchPauseResume a' = do
r <- E.try a' :: IO (Either E.SomeException ())
case r of
Left e -> case E.fromException e of
Just PauseTransfer -> pause
Just ResumeTransfer -> go
_ -> done
_ -> done
done = runAssistant d $
flip MSemN.signal 1 <<~ transferSlots
|
