root / src / Ganeti / WConfd / Monad.hs @ b28f715a
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{-# LANGUAGE MultiParamTypeClasses, TypeFamilies, FlexibleContexts #-} |
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{-| All RPC calls are run within this monad. |
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It encapsulates: |
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* IO operations, |
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* failures, |
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* working with the daemon state. |
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Code that is specific either to the configuration or the lock management, should |
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go into their corresponding dedicated modules. |
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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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|
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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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|
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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.WConfd.Monad |
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( DaemonHandle |
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, dhConfigPath |
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, dhSaveConfigWorker |
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, mkDaemonHandle |
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, WConfdMonadInt |
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, runWConfdMonadInt |
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, WConfdMonad |
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, daemonHandle |
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, modifyConfigState |
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, readConfigState |
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, modifyLockAllocation |
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) where |
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import Control.Applicative |
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import Control.Monad |
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import Control.Monad.Base |
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import Control.Monad.Error |
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import Control.Monad.Reader |
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import Control.Monad.Trans.Control |
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import Data.IORef.Lifted |
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import Ganeti.BasicTypes |
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import Ganeti.Errors |
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import Ganeti.Locking.Locks |
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import Ganeti.Logging |
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import Ganeti.Utils.AsyncWorker |
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import Ganeti.WConfd.ConfigState |
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-- * Pure data types used in the monad |
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-- | The state of the daemon, capturing both the configuration state and the |
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-- locking state. |
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data DaemonState = DaemonState |
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{ dsConfigState :: ConfigState |
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, dsLockAllocation :: GanetiLockAllocation |
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} |
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data DaemonHandle = DaemonHandle |
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{ dhDaemonState :: IORef DaemonState -- ^ The current state of the daemon |
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, dhConfigPath :: FilePath -- ^ The configuration file path |
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-- all static information that doesn't change during the life-time of the |
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-- daemon should go here; |
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-- all IDs of threads that do asynchronous work should probably also go here |
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, dhSaveConfigWorker :: AsyncWorker () |
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} |
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mkDaemonHandle :: FilePath |
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-> ConfigState |
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-> GanetiLockAllocation |
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-> (IO ConfigState -> ResultG (AsyncWorker ())) |
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-- ^ A function that creates a worker that asynchronously |
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-- saves the configuration to the master file. |
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-> ResultG DaemonHandle |
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mkDaemonHandle cpath cstat lstat saveWorkerFn = do |
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ds <- newIORef $ DaemonState cstat lstat |
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saveWorker <- saveWorkerFn $ dsConfigState `liftM` readIORef ds |
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return $ DaemonHandle ds cpath saveWorker |
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-- * The monad and its instances |
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-- | A type alias for easier referring to the actual content of the monad |
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-- when implementing its instances. |
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type WConfdMonadIntType = ReaderT DaemonHandle IO |
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-- | The internal part of the monad without error handling. |
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newtype WConfdMonadInt a = WConfdMonadInt |
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{ getWConfdMonadInt :: WConfdMonadIntType a } |
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instance Functor WConfdMonadInt where |
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fmap f = WConfdMonadInt . fmap f . getWConfdMonadInt |
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instance Applicative WConfdMonadInt where |
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pure = WConfdMonadInt . pure |
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WConfdMonadInt f <*> WConfdMonadInt k = WConfdMonadInt $ f <*> k |
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instance Monad WConfdMonadInt where |
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return = WConfdMonadInt . return |
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(WConfdMonadInt k) >>= f = WConfdMonadInt $ k >>= getWConfdMonadInt . f |
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instance MonadIO WConfdMonadInt where |
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liftIO = WConfdMonadInt . liftIO |
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instance MonadBase IO WConfdMonadInt where |
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liftBase = WConfdMonadInt . liftBase |
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instance MonadBaseControl IO WConfdMonadInt where |
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newtype StM WConfdMonadInt b = StMWConfdMonadInt |
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{ runStMWConfdMonadInt :: StM WConfdMonadIntType b } |
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liftBaseWith f = WConfdMonadInt . liftBaseWith |
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$ \r -> f (liftM StMWConfdMonadInt . r . getWConfdMonadInt) |
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restoreM = WConfdMonadInt . restoreM . runStMWConfdMonadInt |
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instance MonadLog WConfdMonadInt where |
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logAt p = WConfdMonadInt . logAt p |
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-- | Runs the internal part of the WConfdMonad monad on a given daemon |
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-- handle. |
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runWConfdMonadInt :: WConfdMonadInt a -> DaemonHandle -> IO a |
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runWConfdMonadInt (WConfdMonadInt k) = runReaderT k |
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-- | The complete monad with error handling. |
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type WConfdMonad = ResultT GanetiException WConfdMonadInt |
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-- * Basic functions in the monad |
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-- | Returns the daemon handle. |
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daemonHandle :: WConfdMonad DaemonHandle |
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daemonHandle = lift . WConfdMonadInt $ ask |
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-- | Returns the current configuration, given a handle |
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readConfigState :: WConfdMonad ConfigState |
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readConfigState = liftM dsConfigState . readIORef . dhDaemonState |
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=<< daemonHandle |
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-- | Atomically modifies the configuration state in the WConfdMonad. |
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modifyConfigState :: (ConfigState -> (ConfigState, a)) -> WConfdMonad a |
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modifyConfigState f = do |
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dh <- daemonHandle |
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-- TODO: Use lenses to modify the daemons state here |
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let mf ds = let (cs', r) = f (dsConfigState ds) |
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in (ds { dsConfigState = cs' }, r) |
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r <- atomicModifyIORef (dhDaemonState dh) mf |
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-- trigger the config. saving worker and wait for it |
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logDebug "Triggering config write" |
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liftBase . triggerAndWait . dhSaveConfigWorker $ dh |
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logDebug "Config write finished" |
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-- trigger the config. distribution worker asynchronously |
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-- TODO |
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return r |
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-- | Atomically modifies the lock allocation state in WConfdMonad. |
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modifyLockAllocation :: (GanetiLockAllocation -> (GanetiLockAllocation, a)) |
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-> WConfdMonad a |
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modifyLockAllocation f = do |
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dh <- lift . WConfdMonadInt $ ask |
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let mf ds = let (la', r) = f (dsLockAllocation ds) |
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in (ds { dsLockAllocation = la' }, r) |
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atomicModifyIORef (dhDaemonState dh) mf |
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-- TODO: Trigger the async. lock saving worker |