git-annex/Assistant/Threads/Transferrer.hs

{- git-annex assistant data transferrer thread
 -
 - Copyright 2012 Joey Hess <joey@kitenet.net>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

module Assistant.Threads.Transferrer where

import Assistant.Common
import Assistant.ThreadedMonad
import Assistant.DaemonStatus
import Assistant.TransferQueue
import Assistant.TransferSlots
import Assistant.Alert
import Logs.Transfer
import Logs.Location
import Annex.Content
import qualified Remote
import Types.Key
import Locations.UserConfig

import System.Process (create_group)

thisThread :: ThreadName
thisThread = "Transferrer"

{- For now only one transfer is run at a time. -}
maxTransfers :: Int
maxTransfers = 1

{- Dispatches transfers from the queue. -}
transfererThread :: ThreadState -> DaemonStatusHandle -> TransferQueue -> TransferSlots -> IO ()
transfererThread st dstatus transferqueue slots = go =<< readProgramFile
	where
		go program = getNextTransfer transferqueue dstatus notrunning >>= handle program
		handle program Nothing = go program
		handle program (Just (t, info)) = do
			ifM (runThreadState st $ shouldTransfer t info)
				( do
					debug thisThread [ "Transferring:" , show t ]
					notifyTransfer dstatus
					transferThread dstatus slots t info inTransferSlot program
				, do
					debug thisThread [ "Skipping unnecessary transfer:" , show t ]
					-- getNextTransfer added t to the
					-- daemonstatus's transfer map.
					void $ removeTransfer dstatus t
				)
			go program
		{- Skip transfers that are already running. -}
		notrunning i = startedTime i == Nothing

{- Checks if the file to download is already present, or the remote
 - being uploaded to isn't known to have the file. -}
shouldTransfer :: Transfer -> TransferInfo -> Annex Bool
shouldTransfer t info
	| transferDirection t == Download =
		not <$> inAnnex key
	| transferDirection t == Upload =
		{- Trust the location log to check if the
		 - remote already has the key. This avoids
		 - a roundtrip to the remote. -}
		case transferRemote info of
			Nothing -> return False
			Just remote -> 
				notElem (Remote.uuid remote)
					<$> loggedLocations key
	| otherwise = return False
	where
		key = transferKey t

{- A sepeate git-annex process is forked off to run a transfer,
 - running in its own process group. This allows killing it and all its
 - children if the user decides to cancel the transfer.
 -
 - A thread is forked off to run the process, and the thread
 - occupies one of the transfer slots. If all slots are in use, this will
 - block until one becomes available. The thread's id is also recorded in
 - the transfer info; the thread will also be killed when a transfer is
 - stopped, to avoid it displaying any alert about the transfer having
 - failed. -}
transferThread :: DaemonStatusHandle -> TransferSlots -> Transfer -> TransferInfo -> TransferSlotRunner -> FilePath -> IO ()
transferThread dstatus slots t info runner program = case (transferRemote info, associatedFile info) of
	(Nothing, _) -> noop
	(_, Nothing) -> noop
	(Just remote, Just file) -> do
		tid <- runner slots $
			transferprocess remote file
		updateTransferInfo dstatus t $ info { transferTid = Just tid }
	where
		direction = transferDirection t
		isdownload = direction == Download

		transferprocess remote file = void $ do
			(_, _, _, pid)
				<- createProcess (proc program $ toCommand params)
					{ create_group = True }
			status <- waitForProcess pid
			addAlert dstatus $
				makeAlertFiller (status == ExitSuccess) $ 
					transferFileAlert direction file
			where
				params =
					[ Param "transferkey"
					, Param $ key2file $ transferKey t
					, Param $ if isdownload
						then "--from"
						else "--to"
					, Param $ Remote.name remote
					, Param "--file"
					, File file
					]