e5b4d447b6
So that remotes that use a persistent network connection are restarted. A remote might keep open a long duration network connection, and could fail to deal well with losing the connection. This is particularly a concern now that we have external special reotes. An external special remote that is implemented naively might open the connection only when PREPARE is sent, and if it loses connection, throw errors on each request that is made. (Note that the ssh connection caching should not have this problem; if the long-duration ssh process loses connection, the named pipe is disconnected and the next ssh attempt will reconnect. Also, XMPP already deals with disconnection robustly in its own way.) There's no way for git-annex to know if a lost network connection actually affects a given remote, which might have a transfer in process. It does not make sense to force kill the transferkeys process every time the NetWatcher detects a change. (Especially because the NetWatcher sometimes polls 1 change per hour.) In any case, the NetWatcher only detects connection to a network, not disconnection. So if a transfer is in progress over the network, and the network goes down, that will need to time out on its own. An alternate approch that was considered is to use a separate transferkeys process for each remote, and detect when a request fails, and assume that means that process is in a failing state and restart it. The problem with that approach is that if a resource is not available and a remote fails every time, it degrades to starting a new transferkeys process for every file transfer, which is too expensive. Instead, this commit only handles the network reconnection case, and restarts transferkeys only once the network has reconnected and another transfer needs to be made. So, a transferkeys process will be reused for 1 hour, or until the next network connection. ---- The NotificationBroadcaster was rewritten to use TMVars rather than MSampleVars, to allow checking without blocking if a notification has been received. ---- This commit was sponsored by Tobias Brunner.
95 lines
3.2 KiB
Haskell
95 lines
3.2 KiB
Haskell
{- A pool of "git-annex transferkeys" processes
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-
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- Copyright 2013 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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module Assistant.TransferrerPool where
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import Assistant.Common
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import Assistant.Types.TransferrerPool
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import Logs.Transfer
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import Utility.Batch
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import qualified Command.TransferKeys as T
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import Control.Concurrent.STM hiding (check)
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import System.Process (create_group, std_in, std_out)
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import Control.Exception (throw)
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import Control.Concurrent
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{- Runs an action with a Transferrer from the pool.
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-
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- Only one Transferrer is left running in the pool at a time.
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- So if this needed to start a new Transferrer, it's stopped when done.
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-}
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withTransferrer :: FilePath -> BatchCommandMaker -> TransferrerPool -> (Transferrer -> IO a) -> IO a
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withTransferrer program batchmaker pool a = do
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i@(TransferrerPoolItem (Just t) _) <- maybe
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(mkTransferrerPoolItem pool =<< mkTransferrer program batchmaker)
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(checkTransferrerPoolItem program batchmaker)
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=<< atomically (popTransferrerPool pool)
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v <- tryNonAsync $ a t
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sz <- atomically $ pushTransferrerPool pool i
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when (sz > 1) $
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void $ forkIO $ stopTransferrer t
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either throw return v
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{- Check if a Transferrer from the pool is still ok to be used.
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- If not, stop it and start a new one. -}
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checkTransferrerPoolItem :: FilePath -> BatchCommandMaker -> TransferrerPoolItem -> IO TransferrerPoolItem
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checkTransferrerPoolItem program batchmaker i = case i of
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TransferrerPoolItem (Just t) check -> ifM check
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( return i
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, do
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stopTransferrer t
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new check
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)
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TransferrerPoolItem Nothing check -> new check
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where
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new check = do
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t <- mkTransferrer program batchmaker
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return $ TransferrerPoolItem (Just t) check
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{- Requests that a Transferrer perform a Transfer, and waits for it to
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- finish. -}
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performTransfer :: Transferrer -> Transfer -> AssociatedFile -> IO Bool
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performTransfer transferrer t f = catchBoolIO $ do
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T.sendRequest t f (transferrerWrite transferrer)
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T.readResponse (transferrerRead transferrer)
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{- Starts a new git-annex transferkeys process, setting up handles
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- that will be used to communicate with it. -}
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mkTransferrer :: FilePath -> BatchCommandMaker -> IO Transferrer
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mkTransferrer program batchmaker = do
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{- It runs as a batch job. -}
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let (program', params') = batchmaker (program, [Param "transferkeys"])
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{- It's put into its own group so that the whole group can be
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- killed to stop a transfer. -}
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(Just writeh, Just readh, _, pid) <- createProcess
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(proc program' $ toCommand params')
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{ create_group = True
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, std_in = CreatePipe
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, std_out = CreatePipe
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}
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fileEncoding readh
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fileEncoding writeh
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return $ Transferrer
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{ transferrerRead = readh
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, transferrerWrite = writeh
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, transferrerHandle = pid
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}
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{- Checks if a Transferrer is still running. If not, makes a new one. -}
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checkTransferrer :: FilePath -> BatchCommandMaker -> Transferrer -> IO Transferrer
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checkTransferrer program batchmaker t =
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maybe (return t) (const $ mkTransferrer program batchmaker)
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=<< getProcessExitCode (transferrerHandle t)
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{- Closing the fds will stop the transferrer. -}
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stopTransferrer :: Transferrer -> IO ()
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stopTransferrer t = do
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hClose $ transferrerRead t
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hClose $ transferrerWrite t
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void $ waitForProcess $ transferrerHandle t
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