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{-| Ganeti lock structure

-}

{-

Copyright (C) 2014 Google Inc.

This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2 of the License, or

(at your option) any later version.

This program is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program; if not, write to the Free Software

Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301, USA.

-}

module Ganeti.Locking.Locks

  ( GanetiLocks(..)

  , GanetiLockAllocation

  , loadLockAllocation

  ) where

import Control.Monad (liftM, (>=>))

import qualified Text.JSON as J

import Ganeti.BasicTypes

import Ganeti.Errors (ResultG)

import Ganeti.JSON (asJSObject, fromObj, fromJResultE)

import Ganeti.Locking.Allocation

import Ganeti.Locking.Types

import Ganeti.Types

-- | The type of Locks available in Ganeti. The order of this type

-- is the lock oder.

data GanetiLocks = BGL deriving (Ord, Eq, Show)

-- TODO: add the remaining locks

-- | Describe the parts the pieces of information that are needed to

-- describe the lock.

lockData :: GanetiLocks -> [(String, J.JSValue)]

lockData BGL = [("type", J.showJSON "BGL")]

-- | Read a lock form its JSON representation.

readLock :: J.JSValue -> J.Result GanetiLocks

readLock v =  do

  fields <- liftM J.fromJSObject $ asJSObject v

  tp <- fromObj fields "type"

  case tp of

    "BGL" -> return BGL

    _ -> fail $ "Unknown lock type " ++ tp

instance J.JSON GanetiLocks where

  showJSON = J.JSObject . J.toJSObject . lockData

  readJSON = readLock

instance Lock GanetiLocks where

  lockImplications BGL = []

-- | The type of lock Allocations in Ganeti. In Ganeti, the owner of

-- locks are jobs.

type GanetiLockAllocation = LockAllocation GanetiLocks JobId

-- | Load a lock allocation from disk.

loadLockAllocation :: FilePath -> ResultG GanetiLockAllocation

loadLockAllocation =

  liftIO . readFile

  >=> fromJResultE "parsing lock allocation" . J.decodeStrict