aboutsummaryrefslogtreecommitdiff
path: root/Assistant/TransferSlots.hs
blob: 7c9f7470234ca97f724715c684151f14783b07d1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
{- 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