93 lines
3 KiB
Haskell
93 lines
3 KiB
Haskell
{- Adds hooks to remotes.
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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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module Remote.Helper.Hooks (addHooks) where
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import qualified Data.Map as M
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import Common.Annex
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import Types.Remote
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import qualified Annex
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import Annex.LockPool
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import Config
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import Annex.Perms
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{- Modifies a remote's access functions to first run the
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- annex-start-command hook, and trigger annex-stop-command on shutdown.
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- This way, the hooks are only run when a remote is actively being used.
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-}
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addHooks :: Remote -> Annex Remote
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addHooks r = addHooks' r <$> lookupHook r "start" <*> lookupHook r "stop"
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addHooks' :: Remote -> Maybe String -> Maybe String -> Remote
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addHooks' r Nothing Nothing = r
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addHooks' r starthook stophook = r'
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where
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r' = r
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{ storeKey = \k -> wrapper $ storeKey r k
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, retrieveKeyFile = \k f -> wrapper $ retrieveKeyFile r k f
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, retrieveKeyFileCheap = \k f -> wrapper $ retrieveKeyFileCheap r k f
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, removeKey = \k -> wrapper $ removeKey r k
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, hasKey = \k -> wrapper $ hasKey r k
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}
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where
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wrapper = runHooks r' starthook stophook
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runHooks :: Remote -> Maybe String -> Maybe String -> Annex a -> Annex a
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runHooks r starthook stophook a = do
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dir <- fromRepo gitAnnexRemotesDir
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let lck = dir </> remoteid ++ ".lck"
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whenM (not . any (== lck) . M.keys <$> getPool) $ do
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liftIO $ createDirectoryIfMissing True dir
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firstrun lck
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a
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where
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remoteid = show (uuid r)
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run Nothing = return ()
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run (Just command) = void $ liftIO $
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boolSystem "sh" [Param "-c", Param command]
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firstrun lck = do
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-- Take a shared lock; This indicates that git-annex
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-- is using the remote, and prevents other instances
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-- of it from running the stophook. If another
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-- instance is shutting down right now, this
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-- will block waiting for its exclusive lock to clear.
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lockFile lck
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-- The starthook is run even if some other git-annex
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-- is already running, and ran it before.
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-- It would be difficult to use locking to ensure
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-- it's only run once, and it's also possible for
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-- git-annex to be interrupted before it can run the
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-- stophook, in which case the starthook
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-- would be run again by the next git-annex.
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-- So, requiring idempotency is the right approach.
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run starthook
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Annex.addCleanup (remoteid ++ "-stop-command") $
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runstop lck
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runstop lck = do
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-- Drop any shared lock we have, and take an
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-- exclusive lock, without blocking. If the lock
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-- succeeds, we're the only process using this remote,
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-- so can stop it.
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unlockFile lck
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mode <- annexFileMode
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fd <- liftIO $ noUmask mode $
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openFd lck ReadWrite (Just mode) defaultFileFlags
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v <- liftIO $ tryIO $
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setLock fd (WriteLock, AbsoluteSeek, 0, 0)
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case v of
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Left _ -> return ()
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Right _ -> run stophook
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liftIO $ closeFd fd
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lookupHook :: Remote -> String -> Annex (Maybe String)
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lookupHook r n = go =<< getRemoteConfig (repo r) hookname ""
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where
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go "" = return Nothing
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go command = return $ Just command
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hookname = n ++ "-command"
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