content: {-# LANGUAGE TemplateHaskell, NoMonomorphismRestriction, FlexibleContexts #-}
  
  {-|  The WConfd functions for direct configuration manipulation
  
  This module contains the client functions exported by WConfD for
  specific configuration manipulation.
  
  -}
  
  {-
  
  Copyright (C) 2014 Google Inc.
  All rights reserved.
  
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are
  met:
  
  1. Redistributions of source code must retain the above copyright notice,
  this list of conditions and the following disclaimer.
  
  2. Redistributions in binary form must reproduce the above copyright
  notice, this list of conditions and the following disclaimer in the
  documentation and/or other materials provided with the distribution.
  
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
  IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  -}
  
  module Ganeti.WConfd.ConfigModifications where
  
  import Control.Lens (_2)
  import Control.Lens.Getter ((^.))
  import Control.Lens.Setter ((.~), (%~))
  import qualified Data.ByteString.UTF8 as UTF8
  import Control.Lens.Traversal (mapMOf)
  import Control.Monad (unless, when, forM_, foldM, liftM2)
  import Control.Monad.Except (MonadError, throwError)
  import Control.Monad.Fail (MonadFail)
  import Control.Monad.IO.Class (liftIO)
  import Control.Monad.Trans.State (StateT, get, put, modify,
                                    runStateT, execStateT)
  import Data.Foldable (fold)
  import Data.List (elemIndex)
  import Data.Maybe (isJust, maybeToList, fromMaybe, fromJust)
  import Language.Haskell.TH (Name)
  import System.Time (getClockTime, ClockTime)
  import Text.Printf (printf)
  import qualified Data.Map as M
  import qualified Data.Set as S
  
  import Ganeti.BasicTypes (GenericResult(..), genericResult, toError)
  import Ganeti.Constants (lastDrbdPort)
  import Ganeti.Errors (GanetiException(..))
  import Ganeti.JSON (Container, GenericContainer(..), alterContainerL
                     , lookupContainer, MaybeForJSON(..), TimeAsDoubleJSON(..))
  import Ganeti.Locking.Locks (ClientId, ciIdentifier)
  import Ganeti.Logging.Lifted (logDebug, logInfo)
  import Ganeti.Objects
  import Ganeti.Objects.Lens
  import Ganeti.Types (AdminState, AdminStateSource)
  import Ganeti.WConfd.ConfigState (ConfigState, csConfigData, csConfigDataL)
  import Ganeti.WConfd.Monad (WConfdMonad, modifyConfigWithLock
                             , modifyConfigAndReturnWithLock)
  import qualified Ganeti.WConfd.TempRes as T
  
  type DiskUUID = String
  type InstanceUUID = String
  type NodeUUID = String
  
  -- * accessor functions
  
  getInstanceByUUID :: ConfigState
                    -> InstanceUUID
                    -> GenericResult GanetiException Instance
  getInstanceByUUID cs uuid = lookupContainer
    (Bad . ConfigurationError $
      printf "Could not find instance with UUID %s" uuid)
    (UTF8.fromString uuid)
    (configInstances . csConfigData $ cs)
  
  -- * getters
  
  -- | Gets all logical volumes in the cluster
  getAllLVs :: ConfigState -> S.Set String
  getAllLVs = S.fromList . concatMap getLVsOfDisk . M.elems
            . fromContainer . configDisks  . csConfigData
    where convert (LogicalVolume lvG lvV) = lvG ++ "/" ++ lvV
          getDiskLV :: Disk -> Maybe String
          getDiskLV disk = case diskLogicalId disk of
            Just (LIDPlain lv) -> Just (convert lv)
            _ -> Nothing
          getLVsOfDisk :: Disk -> [String]
          getLVsOfDisk disk = maybeToList (getDiskLV disk)
                            ++ concatMap getLVsOfDisk (diskChildren disk)
  
  -- | Gets the ids of nodes, instances, node groups,
  --   networks, disks, nics, and the cluster itself.
  getAllIDs :: ConfigState -> S.Set String
  getAllIDs cs =
    let lvs = getAllLVs cs
        keysFromC :: GenericContainer a b -> [a]
        keysFromC = M.keys . fromContainer
  
        valuesFromC :: GenericContainer a b -> [b]
        valuesFromC = M.elems . fromContainer
  
        instKeys = keysFromC . configInstances . csConfigData $ cs
        nodeKeys = keysFromC . configNodes . csConfigData $ cs
  
        instValues = map uuidOf . valuesFromC
                   . configInstances . csConfigData $ cs
        nodeValues = map uuidOf . valuesFromC . configNodes . csConfigData $ cs
        nodeGroupValues = map uuidOf . valuesFromC
                        . configNodegroups . csConfigData $ cs
        networkValues = map uuidOf . valuesFromC
                      . configNetworks . csConfigData $ cs
        disksValues = map uuidOf . valuesFromC . configDisks . csConfigData $ cs
  
        nics = map nicUuid . concatMap instNics
             . valuesFromC . configInstances . csConfigData $ cs
  
        cluster = uuidOf . configCluster . csConfigData $ cs
    in S.union lvs . S.fromList $ map UTF8.toString instKeys
         ++ map UTF8.toString nodeKeys
         ++ instValues
         ++ nodeValues
         ++ nodeGroupValues
         ++ networkValues
         ++ disksValues
         ++ map UTF8.toString nics ++ [cluster]
  
  getAllMACs :: ConfigState -> S.Set String
  getAllMACs = S.fromList . map nicMac . concatMap instNics . M.elems
             . fromContainer . configInstances . csConfigData
  
  -- | Checks if the two objects are equal,
  -- excluding timestamps. The serial number of
  -- current must be one greater than that of target.
  --
  -- If this is true, it implies that the update RPC
  -- updated the config, but did not successfully return.
  isIdentical :: (Eq a, SerialNoObjectL a, TimeStampObjectL a)
              => ClockTime
              -> a
              -> a
              -> Bool
  isIdentical now target current = (mTimeL .~ now $ current) ==
    ((serialL %~ (+1)) . (mTimeL .~ now) $ target)
  
  -- | Checks if the two objects given have the same serial number
  checkSerial :: SerialNoObject a => a -> a -> GenericResult GanetiException ()
  checkSerial target current = if serialOf target == serialOf current
    then Ok ()
    else Bad . ConfigurationError $ printf
      "Configuration object updated since it has been read: %d != %d"
      (serialOf current) (serialOf target)
  
  -- | Updates an object present in a container.
  -- The presence of the object in the container
  -- is determined by the uuid of the object.
  --
  -- A check that serial number of the
  -- object is consistent with the serial number
  -- of the object in the container is performed.
  --
  -- If the check passes, the object's serial number
  -- is incremented, and modification time is updated,
  -- and then is inserted into the container.
  replaceIn :: (UuidObject a, TimeStampObjectL a, SerialNoObjectL a)
            => ClockTime
            -> a
            -> Container a
            -> GenericResult GanetiException (Container a)
  replaceIn now target = alterContainerL (UTF8.fromString (uuidOf target)) extract
    where extract Nothing = Bad $ ConfigurationError
            "Configuration object unknown"
          extract (Just current) = do
            checkSerial target current
            return . Just . (serialL %~ (+1)) . (mTimeL .~ now) $ target
  
  -- | Utility fuction that combines the two
  -- possible actions that could be taken when
  -- given a target.
  --
  -- If the target is identical to the current
  -- value, we return the modification time of
  -- the current value, and not change the config.
  --
  -- If not, we update the config.
  updateConfigIfNecessary :: (Monad m, MonadError GanetiException m, Eq a,
                              UuidObject a, SerialNoObjectL a, TimeStampObjectL a)
                          => ClockTime
                          -> a
                          -> (ConfigState -> Container a)
                          -> (ConfigState
                             -> m ((Int, ClockTime), ConfigState))
                          -> ConfigState
                          -> m ((Int, ClockTime), ConfigState)
  updateConfigIfNecessary now target getContainer f cs = do
    let container = getContainer cs
    current <- lookupContainer (toError . Bad . ConfigurationError $
      "Configuraton object unknown")
      (UTF8.fromString (uuidOf target))
      container
    if isIdentical now target current
      then return ((serialOf current, mTimeOf current), cs)
      else f cs
  
  -- * UUID config checks
  
  -- | Checks if the config has the given UUID
  checkUUIDpresent :: UuidObject a
                   => ConfigState
                   -> a
                   -> Bool
  checkUUIDpresent cs a = uuidOf a `S.member` getAllIDs cs
  
  -- | Checks if the given UUID is new (i.e., no in the config)
  checkUniqueUUID :: UuidObject a
                  => ConfigState
                  -> a
                  -> Bool
  checkUniqueUUID cs a = not $ checkUUIDpresent cs a
  
  -- * RPC checks
  
  -- | Verifications done before adding an instance.
  -- Currently confirms that the instance's macs are not
  -- in use, and that the instance's UUID being
  -- present (or not present) in the config based on
  -- weather the instance is being replaced (or not).
  --
  -- TODO: add more verifications to this call;
  -- the client should have a lock on the name of the instance.
  addInstanceChecks :: Instance
                    -> Bool
                    -> ConfigState
                    -> GenericResult GanetiException ()
  addInstanceChecks inst replace cs = do
    let macsInUse = S.fromList (map nicMac (instNics inst))
                    `S.intersection` getAllMACs cs
    unless (S.null macsInUse) . Bad . ConfigurationError $ printf
      "Cannot add instance %s; MAC addresses %s already in use"
      (show $ instName inst) (show macsInUse)
    if replace
      then do
        let check = checkUUIDpresent cs inst
        unless check . Bad . ConfigurationError $ printf
               "Cannot add %s: UUID %s already in use"
               (show $ instName inst) (UTF8.toString (instUuid inst))
      else do
        let check = checkUniqueUUID cs inst
        unless check . Bad . ConfigurationError $ printf
               "Cannot replace %s: UUID %s not present"
               (show $ instName inst) (UTF8.toString (instUuid inst))
  
  addDiskChecks :: Disk
                -> Bool
                -> ConfigState
                -> GenericResult GanetiException ()
  addDiskChecks disk replace cs =
    if replace
      then
        unless (checkUUIDpresent cs disk) . Bad . ConfigurationError $ printf
               "Cannot add %s: UUID %s already in use"
               (show $ diskName disk) (UTF8.toString (diskUuid disk))
      else
        unless (checkUniqueUUID cs disk) . Bad . ConfigurationError $ printf
               "Cannot replace %s: UUID %s not present"
               (show $ diskName disk) (UTF8.toString (diskUuid disk))
  
  attachInstanceDiskChecks :: InstanceUUID
                           -> DiskUUID
                           -> MaybeForJSON Int
                           -> ConfigState
                           -> GenericResult GanetiException ()
  attachInstanceDiskChecks uuidInst uuidDisk idx' cs = do
    let diskPresent = elem uuidDisk . map (UTF8.toString . diskUuid) . M.elems
                    . fromContainer . configDisks . csConfigData $ cs
    unless diskPresent . Bad . ConfigurationError $ printf
      "Disk %s doesn't exist" uuidDisk
  
    inst <- getInstanceByUUID cs uuidInst
    let numDisks = length $ instDisks inst
        idx = fromMaybe numDisks (unMaybeForJSON idx')
  
    when (idx < 0) . Bad . GenericError $
      "Not accepting negative indices"
    when (idx > numDisks) . Bad . GenericError $ printf
      "Got disk index %d, but there are only %d" idx numDisks
  
    let insts = M.elems . fromContainer . configInstances . csConfigData $ cs
    forM_ insts (\inst' -> when (uuidDisk `elem` instDisks inst') . Bad
      . ReservationError $ printf "Disk %s already attached to instance %s"
          uuidDisk (show . fromMaybe "" $ instName inst'))
  
  -- * Pure config modifications functions
  
  attachInstanceDisk' :: InstanceUUID
                      -> DiskUUID
                      -> MaybeForJSON Int
                      -> ClockTime
                      -> ConfigState
                      -> ConfigState
  attachInstanceDisk' iUuid dUuid idx' ct cs =
    let inst = genericResult (error "impossible") id (getInstanceByUUID cs iUuid)
        numDisks = length $ instDisks inst
        idx = fromMaybe numDisks (unMaybeForJSON idx')
  
        insert = instDisksL %~ (\ds -> take idx ds ++ [dUuid] ++ drop idx ds)
        incr = instSerialL %~ (+ 1)
        time = instMtimeL .~ ct
  
        inst' = time . incr . insert $ inst
        disks = updateIvNames idx inst' (configDisks . csConfigData $ cs)
  
        ri = csConfigDataL . configInstancesL
           . alterContainerL (UTF8.fromString iUuid) .~ Just inst'
        rds = csConfigDataL . configDisksL .~ disks
    in rds . ri $ cs
      where updateIvNames :: Int -> Instance -> Container Disk -> Container Disk
            updateIvNames idx inst (GenericContainer m) =
              let dUuids = drop idx (instDisks inst)
                  upgradeIv m' (idx'', dUuid') =
                    M.adjust (diskIvNameL .~ "disk/" ++ show idx'') dUuid' m'
              in GenericContainer $ foldl upgradeIv m
                  (zip [idx..] (fmap UTF8.fromString dUuids))
  
  -- * Monadic config modification functions which can return errors
  
  detachInstanceDisk' :: MonadError GanetiException m
                      => InstanceUUID
                      -> DiskUUID
                      -> ClockTime
                      -> ConfigState
                      -> m ConfigState
  detachInstanceDisk' iUuid dUuid ct cs =
    let resetIv :: MonadError GanetiException m
                => Int
                -> [DiskUUID]
                -> ConfigState
                -> m ConfigState
        resetIv startIdx disks = mapMOf (csConfigDataL . configDisksL)
          (\cd -> foldM (\c (idx, dUuid') -> mapMOf (alterContainerL dUuid')
            (\md -> case md of
              Nothing -> throwError . ConfigurationError $
                printf "Could not find disk with UUID %s" (UTF8.toString dUuid')
              Just disk -> return
                         . Just
                         . (diskIvNameL .~ ("disk/" ++ show idx))
                         $ disk) c)
            cd (zip [startIdx..] (fmap UTF8.fromString disks)))
        iL = csConfigDataL . configInstancesL . alterContainerL
             (UTF8.fromString iUuid)
    in case cs ^. iL of
      Nothing -> throwError . ConfigurationError $
        printf "Could not find instance with UUID %s" iUuid
      Just ist -> case elemIndex dUuid (instDisks ist) of
        Nothing -> return cs
        Just idx ->
          let ist' = (instDisksL %~ filter (/= dUuid))
                   . (instSerialL %~ (+1))
                   . (instMtimeL .~ ct)
                   $ ist
              cs' = iL .~ Just ist' $ cs
              dks = drop (idx + 1) (instDisks ist)
          in resetIv idx dks cs'
  
  removeInstanceDisk' :: MonadError GanetiException m
                      => InstanceUUID
                      -> DiskUUID
                      -> ClockTime
                      -> ConfigState
                      -> m ConfigState
  removeInstanceDisk' iUuid dUuid ct =
    let f cs
          | elem dUuid
            . fold
            . fmap instDisks
            . configInstances
            . csConfigData
            $ cs
          = throwError . ProgrammerError $
          printf "Cannot remove disk %s. Disk is attached to an instance" dUuid
          | elem dUuid
            . foldMap (:[])
            . fmap (UTF8.toString . diskUuid)
            . configDisks
            . csConfigData
            $ cs
          = return
           . ((csConfigDataL . configDisksL . alterContainerL
              (UTF8.fromString dUuid)) .~ Nothing)
           . ((csConfigDataL . configClusterL . clusterSerialL) %~ (+1))
           . ((csConfigDataL . configClusterL . clusterMtimeL) .~ ct)
           $ cs
          | otherwise = return cs
    in (f =<<) . detachInstanceDisk' iUuid dUuid ct
  
  -- * RPCs
  
  -- | Add a new instance to the configuration, release DRBD minors,
  -- and commit temporary IPs, all while temporarily holding the config
  -- lock. Return True upon success and False if the config lock was not
  -- available and the client should retry.
  addInstance :: Instance -> ClientId -> Bool -> WConfdMonad Bool
  addInstance inst cid replace = do
    ct <- liftIO getClockTime
    logDebug $ "AddInstance: client " ++ show (ciIdentifier cid)
               ++ " adding instance " ++ uuidOf inst
               ++ " with name " ++ show (instName inst)
    let setCtime = instCtimeL .~ ct
        setMtime = instMtimeL .~ ct
        addInst i = csConfigDataL . configInstancesL
                    . alterContainerL (UTF8.fromString $ uuidOf i)
                       .~ Just i
        commitRes tr = mapMOf csConfigDataL $ T.commitReservedIps cid tr
    r <- modifyConfigWithLock
           (\tr cs -> do
             toError $ addInstanceChecks inst replace cs
             commitRes tr $ addInst (setMtime . setCtime $ inst) cs)
           . T.releaseDRBDMinors . UTF8.fromString $ uuidOf inst
    logDebug $ "AddInstance: result of config modification is " ++ show r
    return $ isJust r
  
  addInstanceDisk :: InstanceUUID
                  -> Disk
                  -> MaybeForJSON Int
                  -> Bool
                  -> WConfdMonad Bool
  addInstanceDisk iUuid disk idx replace = do
    logInfo $ printf "Adding disk %s to configuration"
              (UTF8.toString (diskUuid disk))
    ct <- liftIO getClockTime
    let addD = csConfigDataL . configDisksL . alterContainerL
               (UTF8.fromString (uuidOf disk))
                 .~ Just disk
        incrSerialNo = csConfigDataL . configSerialL %~ (+1)
    r <- modifyConfigWithLock (\_ cs -> do
             toError $ addDiskChecks disk replace cs
             let cs' = incrSerialNo . addD $ cs
             toError $ attachInstanceDiskChecks iUuid
                 (UTF8.toString (diskUuid disk)) idx cs'
             return $ attachInstanceDisk' iUuid
                 (UTF8.toString (diskUuid disk)) idx ct cs')
         . T.releaseDRBDMinors $ UTF8.fromString (uuidOf disk)
    return $ isJust r
  
  attachInstanceDisk :: InstanceUUID
                     -> DiskUUID
                     -> MaybeForJSON Int
                     -> WConfdMonad Bool
  attachInstanceDisk iUuid dUuid idx = do
    ct <- liftIO getClockTime
    r <- modifyConfigWithLock (\_ cs -> do
             toError $ attachInstanceDiskChecks iUuid dUuid idx cs
             return $ attachInstanceDisk' iUuid dUuid idx ct cs)
         (return ())
    return $ isJust r
  
  -- | Detach a disk from an instance.
  detachInstanceDisk :: InstanceUUID -> DiskUUID -> WConfdMonad Bool
  detachInstanceDisk iUuid dUuid = do
    ct <- liftIO getClockTime
    isJust <$> modifyConfigWithLock
      (const $ detachInstanceDisk' iUuid dUuid ct) (return ())
  
  -- | Detach a disk from an instance and
  -- remove it from the config.
  removeInstanceDisk :: InstanceUUID -> DiskUUID -> WConfdMonad Bool
  removeInstanceDisk iUuid dUuid = do
    ct <- liftIO getClockTime
    isJust <$> modifyConfigWithLock
      (const $ removeInstanceDisk' iUuid dUuid ct) (return ())
  
  -- | Remove the instance from the configuration.
  removeInstance :: InstanceUUID -> WConfdMonad Bool
  removeInstance iUuid = do
    ct <- liftIO getClockTime
    let iL = csConfigDataL . configInstancesL . alterContainerL
             (UTF8.fromString iUuid)
        pL = csConfigDataL . configClusterL . clusterTcpudpPortPoolL
        sL = csConfigDataL . configClusterL . clusterSerialL
        mL = csConfigDataL . configClusterL . clusterMtimeL
  
        -- Add the instances' network port to the cluster pool
        f :: Monad m => StateT ConfigState m ()
        f = get >>= (maybe
          (return ())
          (maybe
            (return ())
            (modify . (pL %~) . (:))
            . instNetworkPort)
          . (^. iL))
  
        -- Release all IP addresses to the pool
        g :: (MonadError GanetiException m, Functor m, MonadFail m) =>
          StateT ConfigState m ()
        g = get >>= (maybe
          (return ())
          (mapM_ (\nic ->
            when ((isJust . nicNetwork $ nic) && (isJust . nicIp $ nic)) $ do
              let network = fromJust . nicNetwork $ nic
              ip <- readIp4Address (fromJust . nicIp $ nic)
              get >>= mapMOf csConfigDataL (T.commitReleaseIp
                                            (UTF8.fromString network) ip) >>= put)
            . instNics)
          . (^. iL))
  
        -- Remove the instance and update cluster serial num, and mtime
        h :: Monad m => StateT ConfigState m ()
        h = modify $ (iL .~ Nothing) . (sL %~ (+1)) . (mL .~ ct)
    isJust <$> modifyConfigWithLock (const $ execStateT (f >> g >> h)) (return ())
  
  -- | Allocate a port.
  -- The port will be taken from the available port pool or from the
  -- default port range (and in this case we increase
  -- highest_used_port).
  allocatePort :: WConfdMonad (MaybeForJSON Int)
  allocatePort = do
    maybePort <- modifyConfigAndReturnWithLock (\_ cs ->
      let portPoolL = csConfigDataL . configClusterL . clusterTcpudpPortPoolL
          hupL = csConfigDataL . configClusterL . clusterHighestUsedPortL
      in case cs ^. portPoolL of
        [] -> if cs ^. hupL >= lastDrbdPort
          then throwError . ConfigurationError $ printf
            "The highest used port is greater than %s. Aborting." lastDrbdPort
          else return (cs ^. hupL + 1, hupL %~ (+1) $ cs)
        (p:ps) -> return (p, portPoolL .~ ps $ cs))
      (return ())
    return . MaybeForJSON $ maybePort
  
  -- | Adds a new port to the available port pool.
  addTcpUdpPort :: Int -> WConfdMonad Bool
  addTcpUdpPort port =
    let pL = csConfigDataL . configClusterL . clusterTcpudpPortPoolL
        f :: Monad m => ConfigState -> m ConfigState
        f = mapMOf pL (return . (port:) . filter (/= port))
    in isJust <$> modifyConfigWithLock (const f) (return ())
  
  -- | Set the instances' status to a given value.
  setInstanceStatus :: InstanceUUID
                    -> MaybeForJSON AdminState
                    -> MaybeForJSON Bool
                    -> MaybeForJSON AdminStateSource
                    -> WConfdMonad (MaybeForJSON Instance)
  setInstanceStatus iUuid m1 m2 m3 = do
    ct <- liftIO getClockTime
    let modifyInstance = maybe id (instAdminStateL .~) (unMaybeForJSON m1)
                       . maybe id (instDisksActiveL .~) (unMaybeForJSON m2)
                       . maybe id (instAdminStateSourceL .~) (unMaybeForJSON m3)
        reviseInstance = (instSerialL %~ (+1))
                       . (instMtimeL .~ ct)
  
        g :: Instance -> Instance
        g i = if modifyInstance i == i
                then i
                else reviseInstance . modifyInstance $ i
  
        iL = csConfigDataL . configInstancesL . alterContainerL
               (UTF8.fromString iUuid)
  
        f :: MonadError GanetiException m => StateT ConfigState m Instance
        f = get >>= (maybe
          (throwError . ConfigurationError $
            printf "Could not find instance with UUID %s" iUuid)
          (liftM2 (>>)
            (modify . (iL .~) . Just)
            return . g)
          . (^. iL))
    MaybeForJSON <$> modifyConfigAndReturnWithLock
      (const $ runStateT f) (return ())
  
  -- | Sets the primary node of an existing instance
  setInstancePrimaryNode :: InstanceUUID -> NodeUUID -> WConfdMonad Bool
  setInstancePrimaryNode iUuid nUuid = isJust <$> modifyConfigWithLock
    (\_ -> mapMOf (csConfigDataL . configInstancesL . alterContainerL
        (UTF8.fromString iUuid))
      (\mi -> case mi of
        Nothing -> throwError . ConfigurationError $
          printf "Could not find instance with UUID %s" iUuid
        Just ist -> return . Just $ (instPrimaryNodeL .~ nUuid) ist))
    (return ())
  
  -- | The configuration is updated by the provided cluster
  updateCluster :: Cluster -> WConfdMonad (MaybeForJSON (Int, TimeAsDoubleJSON))
  updateCluster cluster = do
    ct <- liftIO getClockTime
    r <- modifyConfigAndReturnWithLock (\_ cs -> do
      let currentCluster = configCluster . csConfigData $ cs
      if isIdentical ct cluster currentCluster
        then return ((serialOf currentCluster, mTimeOf currentCluster), cs)
        else do
          toError $ checkSerial cluster currentCluster
          let updateC = (clusterSerialL %~ (+1)) . (clusterMtimeL .~ ct)
          return ((serialOf cluster + 1, ct)
                 , csConfigDataL . configClusterL .~ updateC cluster $ cs))
      (return ())
    return . MaybeForJSON $ fmap (_2 %~ TimeAsDoubleJSON) r
  
  -- | The configuration is updated by the provided node
  updateNode :: Node -> WConfdMonad (MaybeForJSON (Int, TimeAsDoubleJSON))
  updateNode node = do
    ct <- liftIO getClockTime
    let nL = csConfigDataL . configNodesL
        updateC = (clusterSerialL %~ (+1)) . (clusterMtimeL .~ ct)
    r <- modifyConfigAndReturnWithLock (\_ -> updateConfigIfNecessary ct node
      (^. nL) (\cs -> do
        nC <- toError $ replaceIn ct node (cs ^. nL)
        return ((serialOf node + 1, ct), (nL .~ nC)
                  . (csConfigDataL . configClusterL %~ updateC)
                  $ cs)))
      (return ())
    return . MaybeForJSON $ fmap (_2 %~ TimeAsDoubleJSON) r
  
  -- | The configuration is updated by the provided instance
  updateInstance :: Instance -> WConfdMonad (MaybeForJSON (Int, TimeAsDoubleJSON))
  updateInstance inst = do
    ct <- liftIO getClockTime
    let iL = csConfigDataL . configInstancesL
    r <- modifyConfigAndReturnWithLock (\_ -> updateConfigIfNecessary ct inst
      (^. iL) (\cs -> do
        iC <- toError $ replaceIn ct inst (cs ^. iL)
        return ((serialOf inst + 1, ct), (iL .~ iC) cs)))
      (return ())
    return . MaybeForJSON $ fmap (_2 %~ TimeAsDoubleJSON) r
  
  -- | The configuration is updated by the provided nodegroup
  updateNodeGroup :: NodeGroup
                  -> WConfdMonad (MaybeForJSON (Int, TimeAsDoubleJSON))
  updateNodeGroup ng = do
    ct <- liftIO getClockTime
    let ngL = csConfigDataL . configNodegroupsL
    r <- modifyConfigAndReturnWithLock (\_ -> updateConfigIfNecessary ct ng
      (^. ngL) (\cs -> do
        ngC <- toError $ replaceIn ct ng (cs ^. ngL)
        return ((serialOf ng + 1, ct), (ngL .~ ngC) cs)))
      (return ())
    return . MaybeForJSON $ fmap (_2 %~ TimeAsDoubleJSON) r
  
  -- | The configuration is updated by the provided network
  updateNetwork :: Network -> WConfdMonad (MaybeForJSON (Int, TimeAsDoubleJSON))
  updateNetwork net = do
    ct <- liftIO getClockTime
    let nL = csConfigDataL . configNetworksL
    r <- modifyConfigAndReturnWithLock (\_ -> updateConfigIfNecessary ct net
      (^. nL) (\cs -> do
        nC <- toError $ replaceIn ct net (cs ^. nL)
        return ((serialOf net + 1, ct), (nL .~ nC) cs)))
      (return ())
    return . MaybeForJSON $ fmap (_2 %~ TimeAsDoubleJSON) r
  
  -- | The configuration is updated by the provided disk
  updateDisk :: Disk -> WConfdMonad (MaybeForJSON (Int, TimeAsDoubleJSON))
  updateDisk disk = do
    ct <- liftIO getClockTime
    let dL = csConfigDataL . configDisksL
    r <- modifyConfigAndReturnWithLock (\_ -> updateConfigIfNecessary ct disk
      (^. dL) (\cs -> do
        dC <- toError $ replaceIn ct disk (cs ^. dL)
        return ((serialOf disk + 1, ct), (dL .~ dC) cs)))
      . T.releaseDRBDMinors . UTF8.fromString $ uuidOf disk
    return . MaybeForJSON $ fmap (_2 %~ TimeAsDoubleJSON) r
  
  -- * The list of functions exported to RPC.
  
  exportedFunctions :: [Name]
  exportedFunctions = [ 'addInstance
                      , 'addInstanceDisk
                      , 'addTcpUdpPort
                      , 'allocatePort
                      , 'attachInstanceDisk
                      , 'detachInstanceDisk
                      , 'removeInstance
                      , 'removeInstanceDisk
                      , 'setInstancePrimaryNode
                      , 'setInstanceStatus
                      , 'updateCluster
                      , 'updateDisk
                      , 'updateInstance
                      , 'updateNetwork
                      , 'updateNode
                      , 'updateNodeGroup
                      ]
  