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|
{- A pool of "git-annex transferkeys" processes
-
- Copyright 2013 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Assistant.TransferrerPool where
import Assistant.Common
import Assistant.Types.TransferrerPool
import Logs.Transfer
import qualified Command.TransferKeys as T
import Control.Concurrent.STM
import System.Process (create_group)
import Control.Exception (throw)
import Control.Concurrent
{- Runs an action with a Transferrer from the pool. -}
withTransferrer :: FilePath -> TransferrerPool -> (Transferrer -> IO a) -> IO a
withTransferrer program pool a = do
t <- maybe (mkTransferrer program) (checkTransferrer program)
=<< atomically (tryReadTChan pool)
v <- tryNonAsync $ a t
unlessM (putback t) $
void $ forkIO $ stopTransferrer t
either throw return v
where
putback t = atomically $ ifM (isEmptyTChan pool)
( do
writeTChan pool t
return True
, return False
)
{- Requests that a Transferrer perform a Transfer, and waits for it to
- finish. -}
performTransfer :: Transferrer -> Transfer -> AssociatedFile -> IO Bool
performTransfer transferrer t f = catchBoolIO $ do
T.sendRequest t f (transferrerWrite transferrer)
T.readResponse (transferrerRead transferrer)
{- Starts a new git-annex transferkeys process, setting up a pipe
- that will be used to communicate with it. -}
mkTransferrer :: FilePath -> IO Transferrer
mkTransferrer program = do
(myread, twrite) <- createPipe
(tread, mywrite) <- createPipe
mapM_ (\fd -> setFdOption fd CloseOnExec True) [myread, mywrite]
let params =
[ Param "transferkeys"
, Param "--readfd", Param $ show tread
, Param "--writefd", Param $ show twrite
]
{- It's put into its own group so that the whole group can be
- killed to stop a transfer. -}
(_, _, _, pid) <- createProcess (proc program $ toCommand params)
{ create_group = True }
closeFd twrite
closeFd tread
myreadh <- fdToHandle myread
mywriteh <- fdToHandle mywrite
fileEncoding myreadh
fileEncoding mywriteh
return $ Transferrer
{ transferrerRead = myreadh
, transferrerWrite = mywriteh
, transferrerHandle = pid
}
{- Checks if a Transferrer is still running. If not, makes a new one. -}
checkTransferrer :: FilePath -> Transferrer -> IO Transferrer
checkTransferrer program t = maybe (return t) (const $ mkTransferrer program)
=<< getProcessExitCode (transferrerHandle t)
{- Closing the fds will stop the transferrer. -}
stopTransferrer :: Transferrer -> IO ()
stopTransferrer t = do
hClose $ transferrerRead t
hClose $ transferrerWrite t
void $ waitForProcess $ transferrerHandle t
|
