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If not, see . + +Also add information on how to contact you by electronic and paper mail. + + If the program does terminal interaction, make it output a short +notice like this when it starts in an interactive mode: + + Copyright (C) + This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. + This is free software, and you are welcome to redistribute it + under certain conditions; type `show c' for details. + +The hypothetical commands `show w' and `show c' should show the appropriate +parts of the General Public License. Of course, your program's commands +might be different; for a GUI interface, you would use an "about box". + + You should also get your employer (if you work as a programmer) or school, +if any, to sign a "copyright disclaimer" for the program, if necessary. +For more information on this, and how to apply and follow the GNU GPL, see +. + + The GNU General Public License does not permit incorporating your program +into proprietary programs. If your program is a subroutine library, you +may consider it more useful to permit linking proprietary applications with +the library. If this is what you want to do, use the GNU Lesser General +Public License instead of this License. But first, please read +. diff --git a/distributed-fork.cabal b/distributed-fork.cabal new file mode 100644 --- /dev/null +++ b/distributed-fork.cabal @@ -0,0 +1,53 @@ +name: distributed-fork +version: 0.0.1.0 +synopsis: Like 'forkIO', but uses remote machines instead of local threads. +homepage: https://github.com/utdemir/distributed-fork +license: BSD3 +license-file: LICENSE +author: Utku Demir +maintainer: me@utdemir.com +copyright: Utku Demir +category: Control +build-type: Simple +cabal-version: >=1.10 + +description: + This library provides a way to offload a computation to another machine. + . + It uses pluggable 'Backend''s to spawn remote executors. It currently only supports AWS Lambda using library. + . + See for the rationale behind the library and "Control.Distributed.Fork" module for the usage. + +library + hs-source-dirs: src + default-language: Haskell2010 + exposed-modules: Control.Distributed.Fork + , Control.Distributed.Fork.Utils + , Control.Distributed.Fork.LocalProcessBackend + , Control.Distributed.Fork.Backend + other-modules: Control.Distributed.Fork.Internal + ghc-options: -Wall + build-depends: base >= 4.7 && < 5 + , async + , binary + , bytestring + , constraints + , distributed-closure + , exceptions + , stm + , text + , terminal-size + , transformers + , typed-process + +test-suite tests + type: exitcode-stdio-1.0 + hs-source-dirs: test + main-is: Test.hs + default-language: Haskell2010 + ghc-options: -Wall -threaded + build-depends: base >=4.7 && < 5 + , distributed-fork + , tasty + , tasty-hunit + , unix diff --git a/src/Control/Distributed/Fork.hs b/src/Control/Distributed/Fork.hs new file mode 100644 --- /dev/null +++ b/src/Control/Distributed/Fork.hs @@ -0,0 +1,88 @@ +-- | +-- This module provides a common interface for offloading an IO action to remote executors. +-- +-- It uses +-- and +-- library +-- for serializing closures to run remotely. +-- +-- is a good introduction for those. +-- +-- In short, if you you need a @'Closure' a@: +-- +-- * If @a@ is statically known (eg. a top level value, or if it does not +-- depend on anything on the scope), use @static@ keyword coming from +-- @StaticPointers@ extension. +-- +-- * If @a@ is a runtime value, use 'cpure' to lift it to @Closure a@. It will ask +-- for a @('Closure' ('Dict' ('Serializable' a)))@. If there is @('Binary' a)@ and +-- @('Typeable' a)@ instances, you can just use @(static 'Dict')@ for that. +-- +-- One important constraint when using this library is that it assumes the remote +-- environment is capable of executing the exact same binary. On most cases, this +-- requires your host environment to be Linux. In future I plan to provide a set +-- of scripts using Docker to overcome this limitation. +module Control.Distributed.Fork + ( fork + , await + , initDistributedFork + , Backend + , Handle + + , ExecutorStatus (..) + , ExecutorPendingStatus (..) + , ExecutorFinalStatus (..) + + -- * Exceptions + , ExecutorFailedException (..) + + -- * Re-exports + , Serializable + , Closure + , cap + , cpure + , Dict (Dict) + ) where + +-------------------------------------------------------------------------------- +import Control.Distributed.Closure +import Control.Monad +import Control.Monad.Catch +import Data.Text (Text) +-------------------------------------------------------------------------------- +import Control.Distributed.Fork.Internal +-------------------------------------------------------------------------------- + +-- | +-- Asynchronously executes the given function using the 'Backend' and returns +-- an 'Handle'. +-- +-- @ +-- {-\# LANGUAGE StaticPointers #-} +-- +-- import Control.Distributed.Fork +-- import Control.Distributed.Fork.LocalProcessBackend +-- +-- main :: IO () +-- main = do +-- 'initDistributedFork' +-- handle <- 'fork' 'localProcessBackend' (static 'Dict') (static (return "Hello World!")) +-- putStrLn =<< await handle +fork :: Backend + -> Closure (Dict (Serializable a)) + -> Closure (IO a) + -> IO (Handle a) +fork b d c = runBackend d c b + +-- | +-- Blocks until the 'Handle' completes. +-- +-- Can throw 'ExecutorFailedException'. +await :: Handle a -> IO a +await = tryAwait >=> either (throwM . ExecutorFailedException) return + +-------------------------------------------------------------------------------- + +newtype ExecutorFailedException = ExecutorFailedException Text + deriving (Show, Eq) +instance Exception ExecutorFailedException diff --git a/src/Control/Distributed/Fork/Backend.hs b/src/Control/Distributed/Fork/Backend.hs new file mode 100644 --- /dev/null +++ b/src/Control/Distributed/Fork/Backend.hs @@ -0,0 +1,56 @@ +{-| +You only need this module if you want to create a new backend for distributed-fork. + +See 'Control.Distributed.Fork.LocalProcessBackend' for a minimal example. +-} + +module Control.Distributed.Fork.Backend + ( + -- * Writing a 'Backend'. + Backend (..) + , BackendM + , argExecutorMode + + -- * Reporting status + , ExecutorFinalStatus (..) + , ExecutorStatus(..) + , ExecutorPendingStatus (..) + , waiting, waitingDesc + , submitted, submittedDesc + , started, startedDesc + + + -- * Re-exports + , liftIO + , getExecutablePath + ) where + +-------------------------------------------------------------------------------- +import Control.Monad.IO.Class +import Control.Monad.Trans.Reader +import Data.Text (Text) +import System.Environment +-------------------------------------------------------------------------------- +import Control.Distributed.Fork.Internal +-------------------------------------------------------------------------------- + +pendingStatus :: ExecutorPendingStatus -> BackendM () +pendingStatus s = BackendM ask >>= liftIO . ($ s) + +waiting :: BackendM () +waiting = pendingStatus $ ExecutorWaiting Nothing + +waitingDesc :: Text -> BackendM () +waitingDesc = pendingStatus . ExecutorWaiting . Just + +submitted :: BackendM () +submitted = pendingStatus $ ExecutorSubmitted Nothing + +submittedDesc :: Text -> BackendM () +submittedDesc = pendingStatus . ExecutorSubmitted . Just + +started :: BackendM () +started = pendingStatus $ ExecutorStarted Nothing + +startedDesc :: Text -> BackendM () +startedDesc = pendingStatus . ExecutorStarted . Just diff --git a/src/Control/Distributed/Fork/Internal.hs b/src/Control/Distributed/Fork/Internal.hs new file mode 100644 --- /dev/null +++ b/src/Control/Distributed/Fork/Internal.hs @@ -0,0 +1,163 @@ +{-# LANGUAGE DeriveGeneric #-} +{-# LANGUAGE GeneralizedNewtypeDeriving #-} +{-# LANGUAGE LambdaCase #-} +{-# LANGUAGE OverloadedStrings #-} +{-# LANGUAGE ScopedTypeVariables #-} +{-# LANGUAGE StaticPointers #-} +{-# LANGUAGE TypeApplications #-} + +module Control.Distributed.Fork.Internal where + +-------------------------------------------------------------------------------- +import Control.Concurrent +import Control.Concurrent.STM +import Control.Distributed.Closure +import Control.Monad.Catch +import Control.Monad.IO.Class +import Control.Monad.Trans.Reader +import Data.Binary +import qualified Data.ByteString as BS +import qualified Data.ByteString.Lazy as BL +import Data.Monoid ((<>)) +import Data.Text (Text) +import qualified Data.Text as T +import Data.Void +import GHC.Generics +import System.Environment +import System.Exit +import System.IO (stdin) +-------------------------------------------------------------------------------- + +-- | +-- We switch to executor mode only when @argv[1] == argExecutorMode@. +argExecutorMode :: String +argExecutorMode = "DISTRIBUTED_FORK_EXECUTOR_MODE" + +-- | +-- On distributed-fork, we run the same binary both in your machine (called +-- "driver") and in the remote environment (called "executor"). In order for the +-- program to act according to where it is, you should call this function as the +-- first thing in your @main@: +-- +-- @ +-- main = do +-- initDistributedFork +-- ... +-- @ +initDistributedFork :: IO () +initDistributedFork = + getArgs >>= \case + [x] + | x == argExecutorMode -> vacuous runExecutor + _ -> return () + +-- | +-- When on executor mode, we expect a serialised ExecutorClosure from `stdin`, +-- run it and exit. +runExecutor :: IO Void +runExecutor = + BL.hGetContents stdin + >>= unclosure . decode @ExecutorClosure + >> exitSuccess + +-- | +-- An ExecutorClosure is a serialisable IO action. +type ExecutorClosure = Closure (IO ()) + +-- | +-- 'Backend' is responsible for running your functions in a remote environment. +-- +-- See: +-- +-- * 'Control.Distributed.Fork.LocalProcessBackend.localProcessBackend' +-- +-- * +newtype Backend = Backend + { bExecute :: BS.ByteString -> BackendM BS.ByteString + -- ^ Should run the current binary in the target environment, put the given + -- string as standard input and return the executables answer on the standard + -- output. + } + +-- | +-- BackendM is essentially `IO`, but also has the ability to report the status of the +-- executor. +newtype BackendM a = + BackendM (ReaderT (ExecutorPendingStatus -> IO ()) IO a) + deriving (Functor, Applicative, Monad, MonadIO, MonadCatch, MonadThrow) + +instance Binary a => Binary (ExecutorFinalStatus a) + +-- | +-- Given an IO action and a static proof that the result is 'Serializable', this +-- function runs the action using the Backend in a separate thread and returns a +-- 'TVar' holding the 'ExecutorStatus'. +runBackend :: + Closure (Dict (Serializable i)) + -> Closure (IO i) + -> Backend + -> IO (Handle i) +runBackend dict cls (Backend backend) = + case unclosure dict of + Dict -> do + let BackendM m = + backend $ BL.toStrict $ encode @ExecutorClosure (toExecutorClosure dict cls) + t <- atomically (newTVar $ ExecutorPending (ExecutorWaiting Nothing)) + _ <- + forkIO $ do + r <- + either + (\(err :: SomeException) -> + ExecutorFailed $ + "Backend threw an exception: " <> T.pack (show err)) + parseAnswer <$> + try (runReaderT m (atomically . writeTVar t . ExecutorPending)) + atomically $ writeTVar t (ExecutorFinished r) + return () + return $ Handle t + +toExecutorClosure :: Closure (Dict (Serializable a)) -> Closure (IO a) -> Closure (IO ()) +toExecutorClosure dict cls = + case unclosure dict of + Dict -> static run `cap` dict `cap` cls + where + run :: forall a. Dict (Serializable a) -> IO a -> IO () + run Dict a = + (a >>= BL.putStr . encode . ExecutorSucceeded) + `catch` (\(ex :: SomeException) -> + BL.putStr . encode . ExecutorFailed @a $ + "Exception from executor: " <> T.pack (show ex)) + +parseAnswer :: Binary a => BS.ByteString -> ExecutorFinalStatus a +parseAnswer bs = + case decodeOrFail (BL.fromStrict bs) of + Left (_, _, err) -> ExecutorFailed $ "Error decoding answer: " <> T.pack err + Right (_, _, a) -> a + +data ExecutorStatus a + = ExecutorPending ExecutorPendingStatus + | ExecutorFinished (ExecutorFinalStatus a) + +data ExecutorPendingStatus + = ExecutorWaiting (Maybe Text) + | ExecutorSubmitted (Maybe Text) + | ExecutorStarted (Maybe Text) + +data ExecutorFinalStatus a + = ExecutorFailed Text + | ExecutorSucceeded a + deriving (Generic) + +-- | +-- Result of a 'fork' is an Handle where you can 'await' a result. +newtype Handle a = Handle (TVar (ExecutorStatus a)) + +tryAwait :: Handle a -> IO (Either Text a) +tryAwait (Handle t) = do + r <- liftIO . atomically $ + readTVar t >>= \case + ExecutorPending _ -> retry + ExecutorFinished a -> return a + return $ case r of + ExecutorFailed err -> Left err + ExecutorSucceeded a -> Right a diff --git a/src/Control/Distributed/Fork/LocalProcessBackend.hs b/src/Control/Distributed/Fork/LocalProcessBackend.hs new file mode 100644 --- /dev/null +++ b/src/Control/Distributed/Fork/LocalProcessBackend.hs @@ -0,0 +1,18 @@ +module Control.Distributed.Fork.LocalProcessBackend where + +-------------------------------------------------------------------------------- +import qualified Data.ByteString.Lazy as BL +import System.Process.Typed +-------------------------------------------------------------------------------- +import Control.Distributed.Fork.Backend +-------------------------------------------------------------------------------- + +-- | +-- A 'Backend' which uses local processes as executors. Useful for testing. +localProcessBackend :: Backend +localProcessBackend = Backend $ \stdin' -> do + executable <- liftIO getExecutablePath + let conf = + setStdin (byteStringInput $ BL.fromStrict stdin') $ + proc executable [argExecutorMode] + liftIO . fmap BL.toStrict $ readProcessStdout_ conf diff --git a/src/Control/Distributed/Fork/Utils.hs b/src/Control/Distributed/Fork/Utils.hs new file mode 100644 --- /dev/null +++ b/src/Control/Distributed/Fork/Utils.hs @@ -0,0 +1,82 @@ +{-# LANGUAGE LambdaCase #-} + +module Control.Distributed.Fork.Utils where + +-------------------------------------------------------------------------------- +import Control.Monad (forM, unless) +import Control.Concurrent.STM (newTVar, atomically, retry, readTVar, modifyTVar, writeTVar) +import Control.Monad.Trans.State (evalStateT, get, put) +import Control.Monad.IO.Class (liftIO) +import Control.Concurrent.Async (async, wait, waitBoth) +import Control.Exception (throwIO) +import Data.Function (fix) +import Control.Concurrent (threadDelay) +import qualified System.Console.Terminal.Size as TS +-------------------------------------------------------------------------------- +import Control.Distributed.Fork.Internal (Handle (..)) +import Control.Distributed.Fork +-------------------------------------------------------------------------------- + +-- | +-- Runs given closures concurrently using the 'Backend' with a progress bar. +-- +-- Throws 'ExecutorFailedException' if something fails. +mapConcurrentlyWithProgress :: Backend + -> Closure (Dict (Serializable a)) + -> [Closure (IO a)] + -> IO [a] +mapConcurrentlyWithProgress backend dict xs = do + st <- atomically $ newTVar (True, 0::Int, 0::Int, 0::Int, 0::Int) + handles <- mapM (fork backend dict) xs + asyncs <- forM handles $ \(Handle tv) -> + async . flip evalStateT (0, 0, 0, 0) . fix $ \recurse -> do + oldState <- get + (newState, result) <- liftIO $ atomically $ do + (n, r) <- readTVar tv >>= return . \case + ExecutorPending (ExecutorWaiting _) -> ((1, 0, 0, 0), Nothing) + ExecutorPending (ExecutorSubmitted _) -> ((0, 1, 0, 0), Nothing) + ExecutorPending (ExecutorStarted _) -> ((0, 0, 1, 0), Nothing) + ExecutorFinished fr -> ((0, 0, 0, 1), Just fr) + unless (oldState /= n) retry + return (n, r) + put newState + liftIO . atomically $ + modifyTVar st $ \case + (_, s1, s2, s3, s4) -> case (oldState, newState) of + ((o1, o2, o3, o4), (n1, n2, n3, n4)) -> + (True, s1 - o1 + n1, s2 - o2 + n2, s3 - o3 + n3, s4 - o4 + n4) + case result of + Nothing -> recurse + Just (ExecutorFailed err) -> liftIO . throwIO $ ExecutorFailedException err + Just (ExecutorSucceeded x) -> return x + + result <- async $ mapM wait asyncs + + termWidth <- maybe 40 TS.width <$> TS.size :: IO Int + let total = length xs + ratio = fromIntegral total / fromIntegral (termWidth - 2) :: Double + + pbar <- async . fix $ \recurse -> do + (waiting, submitted, started, finished) <- atomically $ + readTVar st >>= \case + (False, _, _, _, _) -> retry + (True, a, b, c, d) -> do + writeTVar st (False, a, b, c, d) + return (a, b, c, d) + + let p c n = replicate (truncate (fromIntegral n / ratio)) c + putStr . concat $ + [ "\r" + , "[" + , p '#' finished + , p ':' started + , p '.' submitted + , p ' ' waiting + , "]" + ] + + if finished < total + then threadDelay 10000 >> recurse + else putStrLn "" + + fst <$> waitBoth result pbar diff --git a/test/Test.hs b/test/Test.hs new file mode 100644 --- /dev/null +++ b/test/Test.hs @@ -0,0 +1,47 @@ +{-# LANGUAGE OverloadedStrings #-} +{-# LANGUAGE StaticPointers #-} + +module Main where + +-------------------------------------------------------------------------------- +import Control.Exception (try) +import System.Posix.Process (getProcessID) +import Test.Tasty +import Test.Tasty.HUnit +-------------------------------------------------------------------------------- +import Control.Distributed.Fork +import Control.Distributed.Fork.LocalProcessBackend +-------------------------------------------------------------------------------- + +main :: IO () +main = do + initDistributedFork + defaultMain tests + +tests :: TestTree +tests = + testGroup + "Tests" + [ testCase "localProcessBackend gives correct result" $ do + ret <- + await =<< fork + localProcessBackend + (static Dict) + (static (return (42 :: Integer, "fortytwo" :: String, Just True))) + ret @?= (42, "fortytwo", Just True) + , testCase "localProcessBackend actually spawns" $ do + localPid <- show <$> getProcessID + remotePid <- + await =<< fork + localProcessBackend + (static Dict) + (static (show <$> getProcessID)) + remotePid /= localPid @? "Spawned process should have a different PID." + , testCase "localProcessBackend handles exceptions" $ do + handle <- fork + localProcessBackend + (static Dict) + (static (return (div 1 0) :: IO Int)) + answer <- try $ await handle + answer @?= Left (ExecutorFailedException "Exception from executor: divide by zero") + ]