{-# LANGUAGE DeriveDataTypeable , ScopedTypeVariables , FlexibleInstances , FlexibleContexts #-} {-# OPTIONS -IControl/Workflow #-} {- | This module contains monadic combinators that express some workflow patterns. see the docAprobal.hs example included in the package EXAMPLE: This fragment below describes the approbal procedure of a document. First the document reference is sent to a list of bosses trough a queue. ithey return a boolean in a return queue ( askUser) the booleans are summed up according with a monoid instance (sumUp) if the resullt is false, the correctWF workflow is executed If the result is True, the pipeline continues to the next stage (`checkValidated`) the next stage is the same process with a new list of users (superbosses). There is a timeout of seven days. The result of the users that voted is summed up according with the same monoid instance if the result is true the document is added to the persistent list of approbed documents if the result is false, the document is added to the persistent list of rejectec documents (@checlkValidated1@) The program can be interrupted at any moment. The Workflow monad will restartWorkflows it at the point where it was interrupted. This example uses queues from "Data.Persistent.Queue" @docApprobal :: Document -> Workflow IO () docApprobal doc = `getWFRef` \>>= docApprobal1 docApprobal1 rdoc= return True \>>= log \"requesting approbal from bosses\" \>>= `sumUp` 0 (map (askUser doc rdoc) bosses) \>>= checkValidated \>>= log \"requesting approbal from superbosses or timeout\" \>>= `sumUp` (7*60*60*24) (map(askUser doc rdoc) superbosses) \>>= checkValidated1 askUser _ _ user False = return False askUser doc rdoc user True = do `step` $ `push` (quser user) rdoc `logWF` (\"wait for any response from the user: \" ++ user) `step` . `pop` $ qdocApprobal (title doc) log txt x = `logWF` txt >> return x checkValidated :: Bool -> `Workflow` IO Bool checkValidated val = case val of False -> correctWF (title doc) rdoc >> return False _ -> return True checkValidated1 :: Bool -> Workflow IO () checkValidated1 val = step $ do case val of False -> `push` qrejected doc _ -> `push` qapproved doc mapM (\u ->deleteFromQueue (quser u) rdoc) superbosses@ -} module Control.Workflow.Patterns( -- * Low level combinators split, merge, select, -- * High level conbinators vote, sumUp, Select(..) ) where import Control.Concurrent.STM import Data.Monoid import qualified Control.Monad.CatchIO as CMC import Control.Workflow.Stat import Control.Workflow import Data.Typeable import Prelude hiding (catch) import Control.Monad import Control.Monad.Trans import Control.Concurrent import Control.Exception.Extensible (Exception,SomeException) import Data.RefSerialize import Control.Workflow.Stat import qualified Data.Vector as V import Data.TCache import Debug.Trace import Data.Maybe data ActionWF a= ActionWF (WFRef(Maybe a)) ThreadId -- (WFRef (String, Bool)) -- | spawn a list of independent workflow 'actions' with a seed value 'a' -- The results are reduced by `merge` or `select` split :: ( Typeable b , Serialize b , HasFork io , CMC.MonadCatchIO io) => [a -> Workflow io b] -> a -> Workflow io [ActionWF b] split actions a = mapM (\ac -> do mv <- newWFRef Nothing th<- fork (ac a >>= \v -> (step . liftIO . atomicallySync . writeWFRef mv . Just) v ) return $ ActionWF mv th ) actions -- | wait for the results and apply the cond to produce a single output in the Workflow monad merge :: ( MonadIO io , Typeable a , Typeable b , Serialize a, Serialize b) => ([a] -> io b) -> [ActionWF a] -> Workflow io b merge cond results= step $ mapM (\(ActionWF mv _ ) -> liftIO (atomically $ readWFRef1 mv) ) results >>= cond -- !> "cond" readWFRef1 :: ( Serialize a , Typeable a) => WFRef (Maybe a) -> STM a readWFRef1 r = do mv <- readWFRef r case mv of Just(Just v) -> return v -- !> "return v" Just Nothing -> retry -- !> "retry" Nothing -> error $ "readWFRef1: workflow not found "++ show r data Select = Select -- ^ select the source output | Discard -- ^ Discard the source output | Continue -- ^ Continue the source process | FinishDiscard -- ^ Discard this output, kill all and return the selected outputs | FinishSelect -- ^ Select this output, kill all and return the selected outputs deriving(Typeable, Read, Show) instance Exception Select -- | select the outputs of the workflows produced by `split` constrained within a timeout. -- The check filter, can select , discard or finish the entire computation before -- the timeout is reached. When the computation finalizes, it kill all -- the pending workflows and return the list of selected outputs -- the timeout is in seconds and it is is in the workflow monad, -- so it is possible to restart the process if interrupted, -- so it can proceed for years. -- -- This is necessary for the modelization of real-life institutional cycles such are political elections -- A timeout of 0 means no timeout. select :: ( Serialize a -- , Serialize [a] , Typeable a , HasFork io , CMC.MonadCatchIO io) => Integer -> (a -> STM Select) -> [ActionWF a] -> Workflow io [a] select timeout check actions= do res <- liftIO $ newTVarIO $ V.generate(length actions) (const Nothing) flag <- getTimeoutFlag timeout parent <- liftIO myThreadId checThreads <- liftIO $ newEmptyMVar count <- liftIO $ newMVar 1 let process = do let check' (ActionWF ac _) i = do liftIO . atomically $ do r <- readWFRef1 ac b <- check r case b of Discard -> return () Select -> addRes i r Continue -> addRes i r >> retry FinishDiscard -> do unsafeIOToSTM $ throwTo parent FinishDiscard FinishSelect -> do addRes i r unsafeIOToSTM $ throwTo parent FinishDiscard n <- liftIO $ CMC.block $ do n <- takeMVar count putMVar count (n+1) return n -- !> ("SELECT" ++ show n) if ( n == length actions) then liftIO $ throwTo parent FinishDiscard else return () `CMC.catch` (\(e :: Select) -> liftIO $ throwTo parent e) ws <- mapM (\(ac,i) -> fork $ check' ac i) $ zip actions [0..] liftIO $ putMVar checThreads ws liftIO $ atomically $ do v <- readTVar flag -- wait fo timeout case v of False -> retry True -> return () throw FinishDiscard where addRes i r= do l <- readTVar res writeTVar res $ l V.// [(i, Just r)] let killall = liftIO $ do ws <- readMVar checThreads liftIO $ mapM_ killThread ws liftIO $ mapM_ (\(ActionWF _ th) -> killThread th)actions -- !> "KILLALL" step $ CMC.catch process -- (WF $ \s -> process >>= \ r -> return (s, r)) (\(e :: Select)-> do liftIO $ return . catMaybes . V.toList =<< atomically ( readTVar res) ) `CMC.finally` killall justify str Nothing = error str justify _ (Just x) = return x -- | spawn a list of workflows and reduces the results according with the 'comp' parameter within a given timeout -- -- @ -- vote timeout actions comp x= -- split actions x >>= select timeout (const $ return Select) >>= comp -- @ vote :: ( Serialize b -- , Serialize [b] , Typeable b , HasFork io , CMC.MonadCatchIO io) => Integer -> [a -> Workflow io b] -> ([b] -> Workflow io c) -> a -> Workflow io c vote timeout actions comp x= split actions x >>= select timeout (const $ return Continue) >>= comp -- | sum the outputs of a list of workflows according with its monoid definition -- -- @ sumUp timeout actions = vote timeout actions (return . mconcat) @ sumUp :: ( Serialize b -- , Serialize [b] , Typeable b , Monoid b , HasFork io , CMC.MonadCatchIO io) => Integer -> [a -> Workflow io b] -> a -> Workflow io b sumUp timeout actions = vote timeout actions (return . mconcat) main= do syncWrite SyncManual r <- exec1 "sumup" $ sumUp 0 [f 1, f 2] "0" print r `CMC.catch` \(e::SomeException) -> syncCache -- !> "syncCache" f :: Int -> String -> Workflow IO String f n s= step ( threadDelay ( 5000000 * n)) >> return ( s ++"1") main2=do syncWrite SyncManual exec1 "split" $ split (take 10 $ repeat (step . print)) "hi" >>= merge (const $ return True) main3=do -- syncWrite SyncManual refs <- exec1 "WFRef" $ do refs <- replicateM 20 $ newWFRef Nothing --"bye initial valoe" mapM (\r -> fork $ unsafeIOtoWF $ atomically $ writeWFRef r $ Just "hi final value") refs return refs mapM (\r -> liftIO (atomically $ readWFRef1 r) >>= print) refs