Workflow-0.8.0.7: Control/Workflow.hs
{-# LANGUAGE OverlappingInstances
, UndecidableInstances
, ExistentialQuantification
, ScopedTypeVariables
, MultiParamTypeClasses
, FlexibleInstances
, FlexibleContexts
, TypeSynonymInstances
, DeriveDataTypeable
, RecordWildCards
, BangPatterns
#-}
{-# OPTIONS -IControl/Workflow #-}
{- | A workflow can be seen as a persistent thread.
The workflow monad writes a log that permit to restore the thread
at the interrupted point. `step` is the (partial) monad transformer for
the Workflow monad. A workflow is defined by its name and, optionally
by the key of the single parameter passed. There primitives for starting workflows
also restart the interrupted workflow when it has been in execution previously.
A small example that print the sequence of integers in te console
if you interrupt the progam, when restarted again, it will
start from the last printed number
@module Main where
import Control.Workflow
import Control.Concurrent(threadDelay)
import System.IO (hFlush,stdout)
mcount n= do `step` $ do
putStr (show n ++ \" \")
hFlush stdout
threadDelay 1000000
mcount (n+1)
return () -- to disambiguate the return type
main= `exec1` \"count\" $ mcount (0 :: Int)@
>>>runghc demos\sequence.hs
>0 1 2 3
>CTRL-C Pressed
>>>runghc demos\sequence.hs
>3 4 5 6 7
>CTRL-C Pressed
>>>runghc demos\sequence.hs
>7 8 9 10 11
...
The program restart at the last saved step.
As you can see, some side effect can be re-executed after recovery if
the log is not complete. This may happen after an unexpected shutdown (in this case)
or due to an asynchronous log writing policy. (see `syncWrite`)
When the step results are big and complex, use the "Data.RefSerialize" package to define the (de)serialization instances
The log size will be reduced. printWFHistory` method will print the structure changes
in each step.
If instead of `RefSerialize`, you use read and show instances, there will
be no reduction. but still it will work, and the log will be readable for debugging purposes.
The RefSerialize istance is automatically derived from Read, Show instances.
Data.Binary instances are also fine for serialization. To use Binary, just define a binary instance
of your data by using `showpBinary` and `readpBinary`.
Within the RefSerialize instance of a structure, you can freely mix
Show,Read RefSerialize and Data Binary instances.
"Control.Workflow.Patterns" contains higher level workflow patterns for handling multiple workflows
"Control.Workflow.Configuration" permits the use of workflows for configuration purposes
-}
module Control.Workflow
(
Stat
, Workflow -- a useful type name
, WorkflowList
, PMonadTrans (..)
, MonadCatchIO (..)
, HasFork(..)
, throw
, Indexable(..)
, keyWF
-- * Start/restart workflows
, start
, exec
, exec1d
, exec1
, exec1nc
, wfExec
, startWF
, restartWorkflows
, WFErrors(..)
-- * Lifting to the Workflow monad
, step
, getWFStat
, stepExec
--, while
--, label
--, stepControl
--, stepDebug
, unsafeIOtoWF
-- * References to intermediate values in the workflow log
, WFRef
, newWFRef
, stepWFRef
, readWFRef
-- * State manipulation
, writeWFRef
, moveState
-- * Workflow inspection
, waitWFActive
, getAll
--, getStep
, safeFromIDyn
, getWFKeys
, getWFHistory
, waitFor
, waitForSTM
-- * Persistent timeouts
, waitUntilSTM
, getTimeoutFlag
, withTimeout
, withKillTimeout
-- * Trace logging
, logWF
-- * Termination of workflows
, clearRunningFlag
, killThreadWF
, killWF
, delWF
, killThreadWF1
, delWFHistory
, delWFHistory1
-- * Log writing policy
, syncWrite
, SyncMode(..)
-- * Print log history
, showHistory
, isInRecover
-- * Low leve, internal use
, runWF1
, getState
)
where
import Prelude hiding (catch)
import System.IO.Unsafe
import Control.Monad(when,liftM)
import Control.Applicative
import qualified Control.Exception as CE (Exception,AsyncException(ThreadKilled), SomeException, ErrorCall, throwIO, handle,finally,catch,block,unblock)
import Control.Concurrent -- (forkIO,threadDelay, ThreadId, myThreadId, killThread)
import Control.Concurrent.STM
import GHC.Conc(unsafeIOToSTM)
import GHC.Base (maxInt)
import Data.ByteString.Lazy.Char8 as B hiding (index)
import Data.ByteString.Lazy as BL(putStrLn)
import Data.List as L
import Data.Typeable
import System.Time
import Control.Monad.Trans
--import Control.Concurrent.MonadIO(HasFork(..),MVar,newMVar,takeMVar,putMVar,readMVar)
import System.IO(hPutStrLn, stderr)
import Data.List(elemIndex)
import Data.Maybe
import Data.IORef
import System.IO.Unsafe(unsafePerformIO)
import Data.Map as M(Map,fromList,elems, insert, delete, lookup,toList, fromList,keys)
import qualified Control.Monad.CatchIO as CMC
import qualified Control.Exception.Extensible as E
import Data.TCache
import Data.TCache.Defs
import Data.RefSerialize
import Data.Persistent.IDynamic
import Unsafe.Coerce
import System.Mem.StableName
import Control.Workflow.Stat
--import Debug.Trace
--(!>)= flip trace
type Workflow m = WF Stat m -- not so scary
type WorkflowList m a b= M.Map String (a -> Workflow m b)
instance Monad m => Monad (WF s m) where
return x = WF (\s -> return (s, x))
WF g >>= f = WF (\s -> do
(s1, x) <- g s
let WF fun= f x
fun s1)
instance (Monad m,Functor m) => Functor (Workflow m ) where
fmap f (WF g)= WF (\s -> do
(s1, x) <- g s
return (s1, f x))
tvRunningWfs = getDBRef $ keyRunning :: DBRef Stat
-- | Executes a computation inside of the workflow monad whatever the monad encapsulated in the workflow.
-- Warning: this computation is executed whenever
-- the workflow restarts, no matter if it has been already executed previously. This is useful for intializations or debugging.
-- To avoid re-execution when restarting use: @'step' $ unsafeIOtoWF...@
--
-- To perform IO actions in a workflow that encapsulates an IO monad, use step over the IO action directly:
--
-- @ 'step' $ action @
--
-- instead of
--
-- @ 'step' $ unsafeIOtoWF $ action @
unsafeIOtoWF :: (Monad m) => IO a -> Workflow m a
unsafeIOtoWF x= let y= unsafePerformIO ( x >>= return) in y `seq` return y
{- | @PMonadTrans@ permits |to define a partial monad transformer. They are not defined for all kinds of data
but the ones that have instances of certain classes.That is because in the lift instance code there are some
hidden use of these classes. This also may permit an accurate control of effects.
An instance of MonadTrans is an instance of PMonadTrans
-}
class PMonadTrans t m a where
plift :: Monad m => m a -> t m a
-- | @plift= step@
instance (Monad m
, MonadIO m
, Serialize a
, Typeable a)
=> PMonadTrans (WF Stat) m a
where
plift = step
instance (Monad m, Functor m) => Applicative (Workflow m) where
pure x= return x
WF f <*> WF g= WF $ \s -> do
(s1, k) <- f s
(s2, x) <- g s1
return (s2,k x)
-- | An instance of MonadTrans is an instance of PMonadTrans
instance (MonadTrans t, Monad m) => PMonadTrans t m a where
plift= Control.Monad.Trans.lift
--- | Handle with care: this instance will force
-- the execution at recovery of every liftted IO procedure
-- better use 'step . liftIO' instead of 'liftIO'
instance MonadIO m => MonadIO (WF Stat m) where
liftIO= unsafeIOtoWF
{- | Adapted from the @MonadCatchIO-mtl@ package. However, in this case it is needed to express serializable constraints about the returned values,
so the usual class definitions for lifting IO functions are not suitable.
-}
class MonadCatchIO m a where
-- | Generalized version of 'E.catch'
catch :: E.Exception e => m a -> (e -> m a) -> m a
-- | Generalized version of 'E.block'
block :: m a -> m a
-- | Generalized version of 'E.unblock'
unblock :: m a -> m a
-- | Generalized version of 'E.throwIO'
throw :: (MonadIO m, E.Exception e) => e -> m a
throw = liftIO . E.throwIO
instance (Serialize a
, Typeable a,MonadIO m, CMC.MonadCatchIO m)
=> MonadCatchIO (WF Stat m) a where
catch exp exc = do
expwf <- step $ getTempName
excwf <- step $ getTempName
step $ do
ex <- CMC.catch (exec1d expwf exp >>= return . Right ) $ \e-> return $ Left e
case ex of
Right r -> return r -- All right
Left e ->exec1d excwf (exc e)
-- An exception occured in the main workflow
-- the exception workflow is executed
block exp=WF $ \s -> CMC.block (st exp $ s)
unblock exp= WF $ \s -> CMC.unblock (st exp $ s)
data WFInfo= WFInfo{ name :: String
, finished :: Bool
, haserror :: Maybe WFErrors }
deriving (Typeable,Read, Show)
class MonadIO io => HasFork io where
fork :: io () -> io ThreadId
instance HasFork IO where
fork= forkIO
instance (HasFork io, MonadIO io
, CMC.MonadCatchIO io)
=> HasFork (WF Stat io) where
fork f = do
(r,info@(WFInfo str finished status)) <- stepWFRef $ getTempName >>= \n -> return(WFInfo n False Nothing)
WF $ \s -> do
th <- if finished then fork $ return()
else
fork $
exec1 str f >> labelFinish r str Nothing
`CMC.catch` \(E.ErrorCall str) -> do
liftIO . atomicallySync $ writeWFRef r (WFInfo str True (Just $ WFException str)) -- !> ("ERROR *****"++show e)
killWF1 $ keyWF str ()
`CMC.catch` \(e :: E.SomeException) -> do
liftIO . atomicallySync $ writeWFRef r (WFInfo str True (Just . WFException $ show e)) -- !> ("ERROR *****"++show e)
killWF1 $ keyWF str ()
return (s,th)
where
labelFinish r str err= liftIO . atomicallySync $ writeWFRef r (WFInfo str True err) -- !> "finished"
-- | Start or restart an anonymous workflow inside another workflow.
-- Its state is deleted when finished and the result is stored in
-- the parent's WF state.
wfExec
:: (Serialize a, Typeable a
, CMC.MonadCatchIO m, MonadIO m)
=> Workflow m a -> Workflow m a
wfExec f= do
str <- step $ getTempName
step $ exec1 str f
-- | A version of exec1 that deletes its state after complete execution or thread killed
exec1d :: (MonadIO m, CMC.MonadCatchIO m)
=> String -> (Workflow m b) -> m b
exec1d str f= do
r <- exec1 str f
delit
return r
`CMC.catch` (\e@CE.ThreadKilled -> delit >> throw e)
where
delit= do
delWF str ()
-- | A version of exec with no seed parameter.
exec1 :: ( Monad m, MonadIO m, CMC.MonadCatchIO m)
=> String -> Workflow m a -> m a
exec1 str f= exec str (const f) ()
-- | Start or continue a workflow with exception handling
-- the workflow flags are updated even in case of exception
-- `WFerrors` are raised as exceptions
exec :: ( Indexable a, Serialize a, Typeable a
, Monad m, MonadIO m, CMC.MonadCatchIO m)
=> String -> (a -> Workflow m b) -> a -> m b
exec str f x =
(do
v <- getState str f x
case v of
Right (name, f, stat) -> do
r <- runWF name (f x) stat
return r
Left err -> CMC.throw err)
`CMC.catch`
(\(e :: CE.SomeException) -> liftIO $ do
let name= keyWF str x
clearRunningFlag name --`debug` ("exception"++ show e)
CMC.throw e )
-- | executes a workflow, but does not mark it as finished even if
-- the process ended.
-- It this case, the workflow just will return the last result.
-- If the workflow was gathering data from user questions for a configuration, then this
-- primitive will store them in the log the first time, and can be retrieve it the next time.
exec1nc :: ( Monad m, MonadIO m, CMC.MonadCatchIO m)
=> String -> Workflow m a -> m a
exec1nc str f =do
v <- getState str f ()
case v of
Left err -> CMC.throw err
Right (name, f, stat) -> do
runWF1 name f stat False
`CMC.catch`
(\(e :: CE.SomeException) -> liftIO $ do
let name= keyWF str ()
clearRunningFlag name --`debug` ("exception"++ show e)
CMC.throw e )
`CMC.finally`
(liftIO . atomically .
when(recover stat) $ do
let ref= self stat
s <- readDBRef ref `justifyM` error ("step: not found: "++ wfName stat)
writeDBRef ref s{recover= False,versions=L.reverse $ versions s})
mv :: MVar Int
mv= unsafePerformIO $ newMVar 0
getTempName :: MonadIO m => m String
getTempName= liftIO $ do
seq <- takeMVar mv
putMVar mv (seq + 1)
TOD t _ <- getClockTime
return $ "anon"++ show t ++ show seq
-- Permits the modification of the workflow state by the procedure being lifted
-- if the boolean value is True. This is used internally for control purposes
--stepControl :: ( Monad m
-- , MonadIO m
-- , Serialize a
-- , Typeable a)
-- => m a
-- -> Workflow m a
--stepControl= stepControl1 True
-- | Lifts a monadic computation to the WF monad, and provides transparent state loging and resuming the computation
-- Note: Side effect can be repeated at recovery time if the log was not complete before shut down
-- see the integer sequence example, above.
step :: ( MonadIO m
, Serialize a
, Typeable a)
=> m a
-> Workflow m a
step mx= WF(\s -> do
let
recovers= recover s
versionss= versions s
-- !> "vvvvvvvvvvvvvvvvvvv"
-- !> (unpack $ runW $ showp $ versions s)
-- !> (show $ references s)
-- !> (show $ "recover="++ show( recover s))
-- !> "^^^^^^^^^^^^^^^^^^^"
if recovers && not (L.null versionss)
then
return (s{versions=L.tail versionss }, fromIDyn $ L.head versionss )
else do
let ref= self s
when (recovers && L.null versionss) $ do
liftIO $ atomically $ do
s' <- readDBRef ref `justifyM` error ("step: not found: "++ wfName s)
writeDBRef ref s'{recover= False,references= references s}
stepExec1 ref mx)
getWFStat :: Monad m => Workflow m (DBRef Stat)
getWFStat= WF $ \s -> return (s,self s)
stepExec
:: (Typeable t, Serialize t, MonadIO m) =>
DBRef Stat -> m t -> m (DBRef Stat, t)
stepExec ref mx= do
(s,x) <- stepExec1 ref mx
return (self s, x)
stepExec1 sref mx= do
x' <- mx
liftIO . atomicallySync $ do
s <- readDBRef sref >>= return . fromMaybe (error $ "step: readDBRef: not found:" ++ keyObjDBRef sref)
let versionss= versions s
dynx= toIDyn x'
ver= dynx: versionss
s'= s{ recover= False, versions = ver, state= state s+1}
writeDBRef sref s'
return (s', x')
--undoStep :: Monad m => Workflow m ()
--undoStep= WF $ \s@Stat{..} -> return(s{state=state-1, versions= L.tail versions},())
-- | True if the workflow in recovery mode, reading the log to recover the process state
isInRecover :: Monad m => Workflow m Bool
isInRecover = WF(\s@Stat{..} ->
if recover && not (L.null versions ) then return(s,True )
else if recover== True then return(s{recover=False}, False)
else return (s,False))
-- | For debugging purposes.
-- At recovery time, instead of returning the stored value from the log
-- , stepDebug executes the computation 'f' as normally.
-- . It permits the exact re-execution of a workflow process
stepDebug :: ( Monad m
, MonadIO m
, Serialize a
, Typeable a)
=> m a
-> Workflow m a
stepDebug f = r
where
r= do
WF(\s ->
let stat= state s
in case recover s && not(L.null $ versions s) of
True -> f >>= \x -> return (s{versions= L.tail $ versions s},x)
False -> stepExec1 (self s) f)
-- Executes a computation 'f' in a loop while the return value meets the condition 'cond' is met.
-- At recovery time, the current state of the loop is restored.
-- The loop restart at the last internal state that was (saved) before shutdown.
--
-- The use of 'while' permits a faster recovery when the loop has many steps and the log is very long, as is the case in
-- MFlow applications,
--while
-- :: MonadIO m =>
-- (b -> Bool) -> Workflow m b -> Workflow m b
--while cond f= do
-- n <- WF $ \s -> return (s,state s - L.length (versions s))
---- do
---- let versionss= versions s
---- if recover s && not (L.null versionss)
---- then return (s{versions=L.tail versionss }, fromIDyn $ L.head versionss )
----
---- else return(s{recover= False, state=state s + 1
---- ,versions= (toIDyn $ state s):versionss}
---- ,state s)
-- while1 n
-- where
-- while1 n =do
-- label n
-- x <- f
-- if cond x
-- then while1 n
-- else return x
--
--data Label= Label Int deriving (Eq,Typeable,Read,Show)
--label n = do
-- let !label= Label n
-- r <- isInRecover
-- if r
-- then WF(\s@Stat{..} ->
-- let !label@(Label n) = fromIDyn $ L.head versions
-- !vers = filterMax (\d -> Just label /= safeFromIDyn d) versions -- !> (show label)
-- in return (s{versions= L.tail vers}, fromIDyn . L.head $ vers ))
-- else do
-- step $ return label
-- where
-- filterMax f xs=
-- case L.dropWhile f (L.tail xs) of
-- [] -> xs
-- [_] -> xs
-- xs' -> filterMax f xs'
--
-- | Start or continue a workflow .
-- 'WFErrors' and exceptions are returned as @Left err@ (even if they were triggered as exceptions).
-- Other exceptions are returned as @Left (Exception e)@
-- use `killWF` or `delWF` in case of error to clear the log.
start
:: ( CMC.MonadCatchIO m
, MonadIO m
, Indexable a
, Serialize a
, Typeable a)
=> String -- ^ name that identifies the workflow.
-> (a -> Workflow m b) -- ^ workflow to execute
-> a -- ^ initial value (ever use the initial value for restarting the workflow)
-> m (Either WFErrors b) -- ^ result of the computation
start namewf f1 v = do
ei <- getState namewf f1 v
case ei of
Left error -> return $ Left error
Right (name, f, stat) ->
runWF name (f v) stat >>= return . Right
`CMC.catch`
(\(e :: WFErrors) -> do
let name= keyWF namewf v
clearRunningFlag name
return $ Left e )
`CMC.catch`
(\(E.ErrorCall msg) ->do
let name= keyWF namewf v
clearRunningFlag name
return . Left $ WFException msg )
`CMC.catch`
(\(e :: CE.SomeException) -> liftIO $ do
let name= keyWF namewf v
clearRunningFlag name
return . Left $ WFException $ show e )
-- | Return conditions from the invocation of start/restart primitives
data WFErrors = NotFound | AlreadyRunning | Timeout | WFException String deriving (Typeable, Read, Show)
--instance Show WFErrors where
-- show NotFound= "Not Found"
-- show AlreadyRunning= "Already Running"
-- show Timeout= "Timeout"
-- show (Exception e)= "Exception: "++ show e
--instance Serialize WFErrors where
-- showp NotFound= insertString "NotFound"
-- showp AlreadyRunning= insertString "AlreadyRunning"
-- showp Timeout= insertString "Timeout"
-- showp (Exception e)= insertString "Exception: ">> showp e
--
-- readp= choice[notfound,already,timeout, exc]
-- where
-- notfound= symbol "NotFound" >> return NotFound
-- already= symbol "AlreadyRunning" >> return AlreadyRunning
-- timeout= symbol "Timeout" >> return Timeout
-- exc= symbol "Exception" >> readp >>= \s -> return (Exception s)
instance CE.Exception WFErrors
{-
lookup for any workflow for the entry value v
if namewf is found and is running, return arlready running
if is not runing, restart it
else start anew.
-}
getState :: (Monad m, MonadIO m, Indexable a, Serialize a, Typeable a)
=> String -> x -> a
-> m (Either WFErrors (String, x, Stat))
getState namewf f v= liftIO . atomically $ getStateSTM
where
getStateSTM = do
mrunning <- readDBRef tvRunningWfs
case mrunning of
Nothing -> do
writeDBRef tvRunningWfs (Running $ fromList [])
getStateSTM
Just(Running map) -> do
let key= keyWF namewf v
dynv= toIDyn v
stat1= stat0{wfName= key,versions=[dynv],state=1, self= sref`seq`sref}
sref= getDBRef $ keyResource stat1
case M.lookup key map of
Nothing -> do -- no workflow started for this object
mythread <- unsafeIOToSTM $ myThreadId
safeIOToSTM $ delResource stat1 >> writeResource stat1
writeDBRef tvRunningWfs . Running $ M.insert key (namewf,Just mythread) map
writeDBRef sref stat1
return $ Right (key, f, stat1) -- !> "NEW WF"
Just (wf, started) -> -- a workflow has been initiated for this object
if isJust started
then return $ Left AlreadyRunning -- !> "already running"
else do
mst <- readDBRef sref -- !> "has been running but not running now"
stat' <- case mst of
Nothing -> return stat1 -- error $ "getState: Workflow not found: "++ key
Just s' -> do
-- the thread may have been killed by an exception when running
s <- case recover s' of
True -> return s'
False -> do
s'' <- safeIOToSTM $ readResource s' `onNothing` return stat1
let i= state s''
j= state s'
return s'{versions= versions s'' ++ L.reverse ( L.take ( j - i) $ versions s')}
if isJust (timeout s)
then do
tnow <- unsafeIOToSTM getTimeSeconds
if lastActive s+ fromJust(timeout s) > tnow -- !>("lastActive="++show (lastActive s) ++ "tnow="++show tnow)
then
return s{recover= True,timeout=Nothing}
else
-- has been inactive for too much time, clean it
return stat1
else return s{recover= True}
writeDBRef sref stat'
mythread <- unsafeIOToSTM myThreadId
writeDBRef tvRunningWfs . Running $ M.insert key (namewf,Just mythread) map
return $ Right (key, f, stat')
runWF :: ( Monad m, MonadIO m)
=> String -> Workflow m b -> Stat -> m b
runWF n f s = runWF1 n f s True
runWF1 n f s clear= do
(s', v') <- st f s{versions= L.tail $ versions s}
liftIO $ if clear then clearFromRunningList n
else clearRunningFlag n >> return ()
return v'
where
-- eliminate the thread from the list of running workflows but leave the state
clearFromRunningList n = atomicallySync $ do
Just(Running map) <- readDBRef tvRunningWfs -- !> "clearFormRunning"
writeDBRef tvRunningWfs . Running $ M.delete n map
-- flushDBRef (getDBRef n :: DBRef Stat)
-- | Start or continue a workflow from a list of workflows with exception handling.
-- see 'start' for details about exception and error handling
startWF
:: ( CMC.MonadCatchIO m, MonadIO m
, Serialize a, Serialize b
, Typeable a
, Indexable a)
=> String -- ^ Name of workflow in the workflow list
-> a -- ^ Initial value (ever use the initial value even to restart the workflow)
-> WorkflowList m a b -- ^ function to execute
-> m (Either WFErrors b) -- ^ Result of the computation
startWF namewf v wfs=
case M.lookup namewf wfs of
Nothing -> return $ Left NotFound
Just f -> start namewf f v
-- | Re-start the non finished workflows in the list, for all the initial values that they may have been invoked
restartWorkflows
:: (Serialize a, Typeable a)
=> M.Map String (a -> Workflow IO b) -- the list of workflows that implement the module
-> IO () -- Only workflows in the IO monad can be restarted with restartWorkflows
restartWorkflows map = do
mw <- liftIO $ getResource ((Running undefined ) ) -- :: IO (Maybe(Stat a))
case mw of
Nothing -> return ()
Just (Running all) -> mapM_ start . mapMaybe filter . toList $ all
where
filter (a, (b,Nothing)) = Just (b, a)
filter _ = Nothing
start (key, kv)= do
let mf= M.lookup key map
case mf of
Nothing -> return ()
Just f -> do
let st0= stat0{wfName = kv}
mst <- liftIO $ getResource st0
case mst of
Nothing -> error $ "restartWorkflows: workflow not found "++ keyResource st0
Just st-> do
liftIO . forkIO $ runWF key (f (fromIDyn . L.head $ versions st )) st{recover=True} >> return ()
return ()
-- ei <- getState namewf f1 v
-- case ei of
-- Left error -> return $ Left error
-- Right (name, f, stat) ->
-- | Return all the steps of the workflow log. The values are dynamic
--
-- to get all the steps with result of type Int:
-- @all <- `getAll`
-- let lfacts = mapMaybe `safeFromIDyn` all :: [Int]@
getAll :: Monad m => Workflow m [IDynamic]
getAll= WF(\s -> return (s, versions s))
--getStep
-- :: (Serialize a, Typeable a, Monad m)
-- => Int -- ^ the step number. If negative, count from the current state backwards
-- -> Workflow m a -- ^ return the n-tn intermediate step result
--getStep i= WF(\s -> do
--
-- let stat= state s
--
-- return (s, if i > 0 && i < stat then fromIDyn $ versions s !! (stat -i-1)
-- else if i <= 0 && i > -stat then fromIDyn $ versions s !! (stat - ind +i-1)
-- else error "getStep: wrong index")
-- )
-- | Return the keys of the workflows that are running with a given prefix
getWFKeys :: String -> IO [String]
getWFKeys wfname= do
mwfs <- atomically $ readDBRef tvRunningWfs
case mwfs of
Nothing -> return []
Just (Running wfs) -> return $ Prelude.filter (L.isPrefixOf wfname) $ M.keys wfs
-- | Return the current state of the computation, in the IO monad
getWFHistory :: (Indexable a, Serialize a) => String -> a -> IO (Maybe Stat)
getWFHistory wfname x= getResource stat0{wfName= keyWF wfname x}
-- | Delete the history of a workflow.
-- Be sure that this WF has finished.
--{-# DEPRECATED delWFHistory, delWFHistory1 "use delWF instead" #-}
delWFHistory name1 x = do
let name= keyWF name1 x
delWFHistory1 name
delWFHistory1 name = do
let proto= stat0{wfName= name}
-- when (isJust mdir) $
-- moveFile (defPath proto ++ key proto) (defPath proto ++ fromJust mdir)
atomically . withSTMResources [] $ const resources{ toDelete= [proto] }
-- | wait until the workflow is restarted
waitWFActive wf= do
r <- threadWF wf
case r of -- wait for change in the wofkflow state
Just (_, Nothing) -> retry
_ -> return ()
where
threadWF wf= do
Just(Running map) <- readDBRef tvRunningWfs
return $ M.lookup wf map
-- | Kill the executing thread if not killed, but not its state.
-- `exec` `start` or `restartWorkflows` will continue the workflow
killThreadWF :: ( Indexable a
, Serialize a
, Typeable a
, MonadIO m)
=> String -> a -> m()
killThreadWF wfname x= do
let name= keyWF wfname x
killThreadWF1 name
-- | A version of `KillThreadWF` for workflows started wit no parameter by `exec1`
killThreadWF1 :: MonadIO m => String -> m()
killThreadWF1 name= killThreadWFm name >> return ()
killThreadWFm name= do
(map,f) <- clearRunningFlag name
case f of
Just th -> liftIO $ killThread th
Nothing -> return()
return map
-- | Kill the process (if running) and drop it from the list of
-- restart-able workflows. Its state history remains , so it can be inspected with
-- `getWfHistory` `printWFHistory` and so on.
--
-- When the workflow has been called with no parameter, use: ()
--
killWF :: (Indexable a,MonadIO m) => String -> a -> m ()
killWF name1 x= do
let name= keyWF name1 x
killWF1 name
killWF1 :: MonadIO m => String -> m ()
killWF1 name = do
map <- killThreadWFm name
liftIO . atomically . writeDBRef tvRunningWfs . Running $ M.delete name map
return ()
-- | Delete the WF from the running list and delete the workflow state from persistent storage.
-- Use it to perform cleanup if the process has been killed.
--
-- When the workflow has been called with no parameter, use: ()
delWF :: ( Indexable a
, MonadIO m
, Typeable a)
=> String -> a -> m()
delWF name1 x= do
let name= keyWF name1 x
delWF1 name
delWF1 :: MonadIO m => String -> m()
delWF1 name= liftIO $ atomicallySync $ do
mrun <- readDBRef tvRunningWfs
case mrun of
Nothing -> return()
Just (Running map) -> do
writeDBRef tvRunningWfs . Running $! M.delete name map
delDBRef (getDBRef $ keyResource $ stat0{wfName= name} :: DBRef Stat)
clearRunningFlag name= liftIO $ atomically $ do
Running map <- readDBRef tvRunningWfs `onNothing` error ( "clearRunningFLag: no workflow list" ++ name)
case M.lookup name map of
Just(_, Nothing) -> return (map,Nothing)
Just(v, Just th) -> do
writeDBRef tvRunningWfs . Running $ M.insert name (v, Nothing) map
-- flushDBRef (getDBRef $ keyResource stat0{wfName=name} :: DBRef Stat)
return (map,Just th)
Nothing ->
return (map, Nothing)
-- | Log a value in the workflow log and return a reference to it.
--
-- @newWFRef x= `stepWFRef` (return x) >>= return . fst@
newWFRef :: ( Serialize a
, Typeable a
, MonadIO m
, CMC.MonadCatchIO m)
=> a -> Workflow m (WFRef a)
newWFRef x= stepWFRef (return x) >>= return . fst
-- | Execute an step and return a reference to the result besides the result itself
--
stepWFRef :: ( Serialize a
, Typeable a
, MonadIO m)
=> m a -> Workflow m (WFRef a,a)
stepWFRef exp= do
r <- step exp -- !> "stepWFRef"
WF(\s@Stat{..} -> do
let (n,flag)= if recover
then (state - (L.length versions) -1 ,False)
else (state -1 ,True)
ref = WFRef n self
s'= s{references= (n,(toIDyn r,flag)):references }
liftIO $ atomically $ writeDBRef self s'
r `seq` return (s',(ref,r)) )
-- | return a reference to the last logged entry in the workflow
-- In case the type of the reference is not of the type expected, it return an error string.
--getWFRef ::(Typeable b, Serialize b,MonadIO m) => Workflow m (Either String (WFRef b))
--getWFRef= WF $ \s -> liftIO $ doit s
-- where
-- doit s@Stat{..}= do
-- let (n,flag)= if recover
-- then (state - (L.length versions ) -1 ,False)
-- else (state - 1 ,True)
--
-- mr= (safeFromIDyn $ versions !! n !> show n !> show state) `asTypeOf` typeOfRef (doit s)
-- case mr `seq` mr of
-- Left r -> return (s,Left r)
-- Right r -> do
-- let s'= s{references= (n,(toIDyn r,flag)):references }
-- atomically $ writeDBRef self s'
-- let ref = WFRef n self
-- return (s,Right ref)
-- where
-- typeOfRef :: IO (Stat,Either String (WFRef a)) -> Either String a
-- typeOfRef= undefined
--getNRefs wfname= do
-- st <- getResource stat0{wfName= wfname} `onNothing` error ("Workflow not found: "++ wfname)
-- return $ L.length $ references st
-- |return a reference to the last step result
--getWFRef ::(MonadIO m,Serialize a, Typeable a) => Monad m => a -> Workflow m (WFRef a)
--getWFRef r = WF(\s@Stat{..} -> do
-- let (n,flag)= if recover
-- then (state - (L.length versions) -1 ,False)
-- else (state -1 ,True)
-- ref = WFRef n self
-- s'= s{references= (n,(toIDyn r,flag)):references }
-- liftIO $ atomically $ writeDBRef self s'
-- r `seq` return (s',ref) )
-- | Read the content of a Workflow reference. Note that its result is not in the Workflow monad
readWFRef :: ( Serialize a
, Typeable a)
=> WFRef a
-> STM (Maybe a)
readWFRef (WFRef n ref)= do
mst <- readDBRef ref
case mst of
Nothing -> return Nothing
Just st -> do
case L.lookup n $! references st of
Just (r,_) -> return . Just $ fromIDyn r
Nothing -> do
let n1= if recover st then n else state st - n
return . Just . fromIDyn $ versions st !! n1 -- !> (show (L.length $ versions st) ++ " "++ show n1)
-- flushDBRef ref !> "readWFRef"
-- st <- readDBRef ref `justifyM` (error $ "readWFRef: reference has been deleted from storaga: "++ show ref)
-- let elems= case ms of
-- Just s -> versions s ++ (L.reverse $ L.take (state s' - state s) (versions s'))
-- Nothing -> L.reverse $ versions s'
-- x = elems !! n
-- writeDBRef ref s'
-- return . Just $! fromIDyn x
justifyM io y= io >>= return . fromMaybe y
-- | Writes a new value en in the workflow reference, that is, in the workflow log.
-- Why would you use this?. Don't do that!. modifiying the content of the workflow log would
-- change the excution flow when the workflow restarts. This metod is used internally in the package.
-- The best way to communicate with a workflow is trough a persistent queue, using "Data.Persistent.Collection":
--
-- @worflow= exec1 "wf" do
-- r <- `stepWFRef` expr
-- `push` \"queue\" r
-- back <- `pop` \"queueback\"
-- ...
-- @
writeWFRef :: ( Serialize a
, Typeable a)
=> WFRef a
-> a
-> STM ()
writeWFRef r@(WFRef n ref) x= do
mr <- readDBRef ref
case mr of
Nothing -> error $ "writeWFRef: workflow does not exist: " ++ show ref
Just st@Stat{..} ->
writeDBRef ref st{references= add x references} -- !> ("writeWFREF"++ show r)
where
add x xs= (n,(toIDyn x,False)) : L.filter (\(n',_) -> n/=n') xs
-- flushDBRef ref !> "writeWFRef"
-- s <- safeIOToSTM $ readResourceByKey (keyObjDBRef ref) `justifyM` (error $ "writeWFRef: reference has been deleted from storaga: "++ show ref)
-- let elems= versions s ++ (L.reverse $ L.take (state s' - state s) (versions s'))
--
-- (h,t)= L.splitAt n elems
-- elems'= h ++ (toIDyn x:tail' t)
--
-- tail' []= []
-- tail' t = L.tail t
-- elems `seq` writeDBRef ref s{ versions= elems'}
-- safeIOToSTM $ delResource s >> writeResource s{ versions= L.map tosave $ L.reverse elems'}
-- writeDBRef ref s'
-- | Moves the state of workflow with a seed value to become the state of other seed value
-- This may be of interest when the entry value
-- changes its key value but should not initiate a new workflow
-- but continues with the current one
moveState :: (MonadIO m
, Indexable a
, Serialize a
, Typeable a)
=>String -> a -> a -> m ()
moveState wf t t'= liftIO $ do
atomicallySync $ do
mrun <- readDBRef tvRunningWfs
case mrun of
Nothing -> return()
Just (Running map) -> do
let mr= M.lookup n map
let th= case mr of Nothing -> Nothing; Just(_,mt)-> mt
let map'= M.insert n' (wf,th) $ M.delete n map
writeDBRef tvRunningWfs $ Running map'
withSTMResources[stat0{wfName= n}] $ change n
where
n = keyWF wf t
n'= keyWF wf t'
change n [Nothing]= error $ "moveState: Workflow not found: "++ show n
change n [Just s] = resources{toAdd= [s{wfName=n'
,versions = toIDyn t': L.tail( versions s) }]
,toDelete=[s]}
-- | Log a message in the workflow history. I can be printed out with 'printWFhistory'
-- The message is printed in the standard output too
logWF :: MonadIO m => String -> Workflow m ()
logWF str=do
str <- step . liftIO $ do
time <- getClockTime >>= toCalendarTime >>= return . calendarTimeToString
Prelude.putStrLn str
return $ time ++ ": "++ str
WF $ \s -> str `seq` return (s, ())
--------- event handling--------------
-- | Wait until a TCache object (with a certaing key) meet a certain condition (useful to check external actions )
-- NOTE if anoter process delete the object from te cache, then waitForData will no longer work
-- inside the wokflow, it can be used by lifting it :
-- do
-- x <- step $ ..
-- y <- step $ waitForData ...
-- ..
waitForData :: (IResource a, Typeable a)
=> (a -> Bool) -- ^ The condition that the retrieved object must meet
-> a -- ^ a partially defined object for which keyResource can be extracted
-> IO a -- ^ return the retrieved object that meet the condition and has the given key
waitForData f x = atomically $ waitForDataSTM f x
waitForDataSTM :: (IResource a, Typeable a)
=> (a -> Bool) -- ^ The condition that the retrieved object must meet
-> a -- ^ a partially defined object for which keyResource can be extracted
-> STM a -- ^ return the retrieved object that meet the condition and has the given key
waitForDataSTM filter x= do
tv <- newDBRef x
do
mx <- readDBRef tv >>= \v -> return $ cast v
case mx of
Nothing -> retry
Just x ->
case filter x of
False -> retry
True -> return x
-- | Observe the workflow log until a condition is met.
waitFor
:: ( Indexable a, Serialize a, Serialize b, Typeable a
, Indexable b, Typeable b)
=> (b -> Bool) -- ^ The condition that the retrieved object must meet
-> String -- ^ The workflow name
-> a -- ^ the INITIAL value used in the workflow to start it
-> IO b -- ^ The first event that meet the condition
waitFor filter wfname x= atomically $ waitForSTM filter wfname x
waitForSTM
:: ( Indexable a, Serialize a, Serialize b, Typeable a
, Indexable b, Typeable b)
=> (b -> Bool) -- ^ The condition that the retrieved object must meet
-> String -- ^ The workflow name
-> a -- ^ The INITIAL value used in the workflow
-> STM b -- ^ The first event that meet the condition
waitForSTM filter wfname x= do
let name= keyWF wfname x
let tv= getDBRef . keyResource $ stat0{wfName= name} -- `debug` "**waitFor***"
mmx <- readDBRef tv
case mmx of
Nothing -> error ("waitForSTM: Workflow does not exist: "++ name)
Just mx -> do
let Stat{ versions= d:_}= mx
case safeFromIDyn d of
Left _ -> retry -- `debug` "waithFor retry Nothing"
Right x ->
case filter x of
False -> retry -- `debug` "waitFor false filter retry"
True -> return x -- `debug` "waitfor return"
--{-# DEPRECATED waitUntilSTM, getTimeoutFlag "use withTimeout instead" #-}
-- | Start the timeout and return the flag to be monitored by 'waitUntilSTM'
-- This timeout is persistent. This means that the counter is initialized in the first call to getTimeoutFlag
-- no matter if the workflow is restarted. The time during which the worlkflow has been stopped count also.
-- Thus, the wait time can exceed the time between failures.
-- when timeout is 0 means no timeout.
getTimeoutFlag
:: MonadIO m
=> Integer -- ^ wait time in secods. This timing start from the first time that the timeout was started on. Sucessive restarts of the workflow will respect this timing
-> Workflow m (TVar Bool) -- ^ the returned flag in the workflow monad
getTimeoutFlag 0 = WF $ \s -> liftIO $ newTVarIO False >>= \tv -> return (s, tv)
getTimeoutFlag t = do
tnow <- step $ liftIO getTimeSeconds
flag tnow t
where
flag tnow delta = WF $ \s -> do
tv <- liftIO $ newTVarIO False
liftIO $ do
let t = tnow + delta
atomically $ writeTVar tv False
forkIO $ do waitUntil t ; atomically $ writeTVar tv True
return (s, tv)
getTimeSeconds :: IO Integer
getTimeSeconds= do
TOD n _ <- getClockTime
return n
{- | Wait until a certain clock time has passed by monitoring its flag, in the STM monad.
This permits to compose timeouts with locks waiting for data using `orElse`
*example: wait for any respoinse from a Queue if no response is given in 5 minutes, it is returned True.
@
flag \<- 'getTimeoutFlag' $ 5 * 60
ap \<- `step` . atomically $ readSomewhere >>= return . Just `orElse` 'waitUntilSTM' flag >> return Nothing
case ap of
Nothing -> do 'logWF' "timeout" ...
Just x -> do 'logWF' $ "received" ++ show x ...
@
-}
--longWait :: Integer -> Workflow m a -> Workflow m a
--longWait time wf=
-- WF $ \s -> do
-- flag <- getTimeoutFlag time
-- forkIO $ do
-- atomically $ do
-- b <- readTVar flag
-- if b == False then retry else return ()
-- start (wfName s) wf ""
-- myThreadId >>= killThread
waitUntilSTM :: TVar Bool -> STM()
waitUntilSTM tv = do
b <- readTVar tv
if b == False then retry else return ()
-- | Wait until a certain clock time has passed by monitoring its flag, in the IO monad.
-- See `waitUntilSTM`
waitUntil:: Integer -> IO()
waitUntil t= getTimeSeconds >>= \tnow -> wait ((t-tnow)*1000000)
wait :: Integer -> IO()
wait delta= do
let delay | delta < 0= 0
| delta > (fromIntegral maxInt) = maxInt
| otherwise = fromIntegral $ delta
threadDelay $ delay
if delta <= 0 then return () else wait $ delta - (fromIntegral delay )
-- | Return either the result of the STM conputation or Nothing in case of timeout.
-- The computation can retry
-- This timeout is persistent. This means that the counter is initialized in the first call to getTimeoutFlag
-- no matter if the workflow is restarted. The time during which the worlkflow has been stopped count also.
-- Thus, the wait time can exceed the time between failures.
-- when timeout is 0 it means no timeout.
withTimeout :: ( MonadIO m, Typeable a, Serialize a)=> Integer -> STM a -> Workflow m (Maybe a)
withTimeout time f = do
flag <- getTimeoutFlag time
step . liftIO . atomically $ (f >>= return . Just )
`orElse`
(waitUntilSTM flag >> return Nothing)
-- | Executes a computation understanding that it is inside the
-- workflow identified by 'id'. If 'f' finish after 'time'
-- it genetates a 'Timeout' exception which may result in the end of the workflow if the
-- programmer does not catch it.
-- If the workflow is restarted after 'time2' has elapsed, the workflow
-- will restart from the beginning. If not, it will restart after the last logged step.
--
-- Usually @time2> time@
--
-- @time2=0@ means @time2@ is infinite
--withKillTimeout :: CMC.MonadCatchIO m => String -> Int -> Integer -> m a -> m a
--withKillTimeout id time time2 f = do
-- tid <- liftIO myThreadId
-- tstart <- liftIO getTimeSeconds
-- let final= liftIO $ do
-- tnow <- getTimeSeconds
-- let ref = getDBRef $ keyResource $ stat0{wfName=id} -- !> (keyResource $ stat0{wfName=id} )
-- when (time2 /=0) . atomically $ do
-- s <- readDBRef ref `onNothing` error ( "withKillTimeout: Workflow not found: "++ id)
-- writeDBRef ref s{lastActive= tnow,timeout= Just (time2 - fromIntegral (tnow - tstart))}
-- clearRunningFlag id
-- let proc= do
-- twatchdog <- liftIO $ case time of
-- 0 -> return tid
-- _ -> forkIO $ threadDelay (time * 1000000) >> throwTo tid Timeout
-- r <- f
-- liftIO $ killThread twatchdog
-- return r
--
-- proc `CMC.finally` final
withKillTimeout :: CMC.MonadCatchIO m => String -> Int -> Integer -> m a -> m a
withKillTimeout id time time2 f = do
tid <- liftIO myThreadId
twatchdog <- liftIO $ forkIO $ threadDelay (time * 1000000) >> throwTo tid Timeout
r <- f
liftIO $ killThread twatchdog
return r
`CMC.catch` \(e :: WFErrors) ->
case e of
Timeout -> liftIO $ do
tnow <- getTimeSeconds
let ref = getDBRef $ keyResource $ stat0{wfName=id} -- !> (keyResource $ stat0{wfName=id} )
when (time2 /=0) $ atomically $ do
s <- readDBRef ref `onNothing` error ( "withKillTimeout: Workflow not found: "++ id)
writeDBRef ref s{lastActive= tnow,timeout= Just (time2-fromIntegral time)}
syncCache
clearRunningFlag id
throw Timeout -- !> "Timeout 2"
_ -> throw e
transientTimeout 0= atomically $ newTVar False
transientTimeout t= do
flag <- atomically $ newTVar False
forkIO $ threadDelay (t * 1000000) >> atomically (writeTVar flag True)
return flag