8ba9830653
A paused transfer's thread keeps running, keeping the slot in use. This is intentional; pausing a transfer should not let other queued transfers to run in its place.
62 lines
1.7 KiB
Haskell
62 lines
1.7 KiB
Haskell
{- git-annex assistant transfer slots
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-
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- Copyright 2012 Joey Hess <joey@kitenet.net>
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-
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- Licensed under the GNU GPL version 3 or higher.
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-}
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{-# LANGUAGE DeriveDataTypeable #-}
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module Assistant.TransferSlots where
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import qualified Control.Exception as E
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import Control.Concurrent
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import Data.Typeable
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import Common.Annex
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import Utility.ThreadScheduler
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type TransferSlots = QSemN
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{- A special exception that can be thrown to pause or resume a transfer, while
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- keeping its slot in use. -}
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data TransferException = PauseTransfer | ResumeTransfer
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deriving (Show, Eq, Typeable)
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instance E.Exception TransferException
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{- Number of concurrent transfers allowed to be run from the assistant.
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-
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- Transfers launched by other means, including by remote assistants,
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- do not currently take up slots.
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-}
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numSlots :: Int
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numSlots = 1
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newTransferSlots :: IO TransferSlots
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newTransferSlots = newQSemN numSlots
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{- Waits until a transfer slot becomes available, and runs a transfer
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- action in the slot, in its own thread.
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-
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- Note that the action is subject to being killed when the transfer
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- is canceled or paused.
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-
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- A PauseTransfer exception is handled by letting the action be killed,
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- then pausing the thread until a ResumeTransfer exception is raised,
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- then rerunning the action.
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-}
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inTransferSlot :: TransferSlots -> IO () -> IO ThreadId
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inTransferSlot s transfer = do
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waitQSemN s 1
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forkIO $ E.bracket_ noop (signalQSemN s 1) go
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where
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go = catchPauseResume transfer
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pause = catchPauseResume $ runEvery (Seconds 86400) noop
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catchPauseResume a = E.catch a handlePauseResume
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handlePauseResume PauseTransfer = do
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putStrLn "pause"
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pause
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handlePauseResume ResumeTransfer = do
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putStrLn "resume"
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go
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