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{-| Utilities related to livelocks and death detection
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-}
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{-
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Copyright (C) 2014 Google Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301, USA.
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-}
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module Ganeti.Utils.Livelock
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( Livelock
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, mkLivelockFile
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) where
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import qualified Control.Exception as E
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import Control.Monad
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import Control.Monad.Error
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import System.Directory (doesFileExist)
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import System.IO
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import System.Posix.IO
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import System.Posix.Types (Fd)
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import System.Time (ClockTime(..), getClockTime)
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import Ganeti.BasicTypes
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import Ganeti.Path (livelockFile)
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import Ganeti.Utils (lockFile)
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type Livelock = FilePath
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-- | Appends the current time to the given prefix, creates
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-- the lockfile in the appropriate directory, and locks it.
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-- Returns its full path and the file's file descriptor.
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mkLivelockFile :: (Error e, MonadError e m, MonadIO m)
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=> FilePath -> m (Fd, Livelock)
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mkLivelockFile prefix = do
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(TOD secs _) <- liftIO getClockTime
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lockfile <- liftIO . livelockFile $ prefix ++ "_" ++ show secs
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fd <- liftIO (lockFile lockfile) >>= \r -> case r of
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Bad msg -> failError $ "Locking the livelock file " ++ lockfile
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++ ": " ++ msg
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Ok fd -> return fd
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return (fd, lockfile)
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