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{- Running a long or expensive batch operation niced.
-
- Copyright 2013 Joey Hess <joey@kitenet.net>
-
- License: BSD-2-clause
-}
{-# LANGUAGE CPP #-}
module Utility.Batch where
import Common
#if defined(linux_HOST_OS) || defined(__ANDROID__)
import Control.Concurrent.Async
import System.Posix.Process
#endif
import qualified Control.Exception as E
{- Runs an operation, at batch priority.
-
- This is done by running it in a bound thread, which on Linux can be set
- to have a different nice level than the rest of the program. Note that
- due to running in a bound thread, some operations may be more expensive
- to perform. Also note that if the action calls forkIO or forkOS itself,
- that will make a new thread that does not have the batch priority.
-
- POSIX threads do not support separate nice levels, so on other operating
- systems, the action is simply ran.
-}
batch :: IO a -> IO a
#if defined(linux_HOST_OS) || defined(__ANDROID__)
batch a = wait =<< batchthread
where
batchthread = asyncBound $ do
setProcessPriority 0 maxNice
a
#else
batch a = a
#endif
maxNice :: Int
maxNice = 19
{- Makes a command be run by whichever of nice, ionice, and nocache
- are available in the path. -}
type BatchCommandMaker = (String, [CommandParam]) -> (String, [CommandParam])
getBatchCommandMaker :: IO BatchCommandMaker
getBatchCommandMaker = do
#ifndef mingw32_HOST_OS
nicers <- filterM (inPath . fst)
[ ("nice", [])
#ifndef __ANDROID__
-- Android's ionice does not allow specifying a command,
-- so don't use it.
, ("ionice", ["-c3"])
#endif
, ("nocache", [])
]
return $ \(command, params) ->
case nicers of
[] -> (command, params)
(first:rest) -> (fst first, map Param (snd first ++ concatMap (\p -> fst p : snd p) rest ++ [command]) ++ params)
#else
return id
#endif
toBatchCommand :: (String, [CommandParam]) -> IO (String, [CommandParam])
toBatchCommand v = do
batchmaker <- getBatchCommandMaker
return $ batchmaker v
{- Runs a command in a way that's suitable for batch jobs that can be
- interrupted.
-
- If the calling thread receives an async exception, it sends the
- command a SIGTERM, and after the command finishes shuttting down,
- it re-raises the async exception. -}
batchCommand :: String -> [CommandParam] -> IO Bool
batchCommand command params = batchCommandEnv command params Nothing
batchCommandEnv :: String -> [CommandParam] -> Maybe [(String, String)] -> IO Bool
batchCommandEnv command params environ = do
batchmaker <- getBatchCommandMaker
let (command', params') = batchmaker (command, params)
let p = proc command' $ toCommand params'
(_, _, _, pid) <- createProcess $ p { env = environ }
r <- E.try (waitForProcess pid) :: IO (Either E.SomeException ExitCode)
case r of
Right ExitSuccess -> return True
Right _ -> return False
Left asyncexception -> do
terminateProcess pid
void $ waitForProcess pid
E.throwIO asyncexception
|
