streamly-0.8.1: src/Streamly/Internal/Data/Stream/StreamD/Exception.hs
-- |
-- Module : Streamly.Internal.Data.Stream.StreamD.Exception
-- Copyright : (c) 2020 Composewell Technologies and Contributors
-- License : BSD-3-Clause
-- Maintainer : streamly@composewell.com
-- Stability : experimental
-- Portability : GHC
module Streamly.Internal.Data.Stream.StreamD.Exception
(
gbracket_
, gbracket
, before
, after_
, after
, bracket_
, bracket'
, onException
, finally_
, finally
, ghandle
, handle
, retry
)
where
#include "inline.hs"
import Control.Exception (Exception, SomeException, mask_)
import Control.Monad.Catch (MonadCatch)
import Control.Monad.IO.Class (MonadIO(..))
import Control.Monad.Trans.Control (MonadBaseControl, liftBaseOp_)
import Data.Map.Strict (Map)
import GHC.Exts (inline)
import Streamly.Internal.Control.Concurrent (MonadAsync)
import Streamly.Internal.Data.IOFinalizer
(newIOFinalizer, runIOFinalizer, clearingIOFinalizer)
import qualified Control.Monad.Catch as MC
import qualified Data.Map.Strict as Map
import Streamly.Internal.Data.Stream.StreamD.Type
data GbracketState s1 s2 v
= GBracketInit
| GBracketNormal s1 v
| GBracketException s2
-- | Like 'gbracket' but with following differences:
--
-- * alloc action @m c@ runs with async exceptions enabled
-- * cleanup action @c -> m d@ won't run if the stream is garbage collected
-- after partial evaluation.
-- * does not require a 'MonadAsync' constraint.
--
-- /Inhibits stream fusion/
--
-- /Pre-release/
--
{-# INLINE_NORMAL gbracket_ #-}
gbracket_
:: Monad m
=> m c -- ^ before
-> (forall s. m s -> m (Either e s)) -- ^ try (exception handling)
-> (c -> m d) -- ^ after, on normal stop
-> (c -> e -> Stream m b -> Stream m b) -- ^ on exception
-> (c -> Stream m b) -- ^ stream generator
-> Stream m b
gbracket_ bef exc aft fexc fnormal =
Stream step GBracketInit
where
{-# INLINE_LATE step #-}
step _ GBracketInit = do
r <- bef
return $ Skip $ GBracketNormal (fnormal r) r
step gst (GBracketNormal (UnStream step1 st) v) = do
res <- exc $ step1 gst st
case res of
Right r -> case r of
Yield x s ->
return $ Yield x (GBracketNormal (Stream step1 s) v)
Skip s -> return $ Skip (GBracketNormal (Stream step1 s) v)
Stop -> aft v >> return Stop
-- XXX Do not handle async exceptions, just rethrow them.
Left e ->
return $ Skip (GBracketException (fexc v e (UnStream step1 st)))
step gst (GBracketException (UnStream step1 st)) = do
res <- step1 gst st
case res of
Yield x s -> return $ Yield x (GBracketException (Stream step1 s))
Skip s -> return $ Skip (GBracketException (Stream step1 s))
Stop -> return Stop
data GbracketIOState s1 s2 v wref
= GBracketIOInit
| GBracketIONormal s1 v wref
| GBracketIOException s2
-- | Run the alloc action @m c@ with async exceptions disabled but keeping
-- blocking operations interruptible (see 'Control.Exception.mask'). Use the
-- output @c@ as input to @c -> Stream m b@ to generate an output stream. When
-- generating the stream use the supplied @try@ operation @forall s. m s -> m
-- (Either e s)@ to catch synchronous exceptions. If an exception occurs run
-- the exception handler @c -> e -> Stream m b -> m (Stream m b)@. Note that
-- 'gbracket' does not rethrow the exception, it has to be done by the
-- exception handler if desired.
--
-- The cleanup action @c -> m d@, runs whenever the stream ends normally, due
-- to a sync or async exception or if it gets garbage collected after a partial
-- lazy evaluation. See 'bracket' for the semantics of the cleanup action.
--
-- 'gbracket' can express all other exception handling combinators.
--
-- /Inhibits stream fusion/
--
-- /Pre-release/
{-# INLINE_NORMAL gbracket #-}
gbracket
:: (MonadIO m, MonadBaseControl IO m)
=> m c -- ^ before
-> (forall s. m s -> m (Either e s)) -- ^ try (exception handling)
-> (c -> m d1) -- ^ on normal stop
-> (c -> m d2) -- ^ on GC without normal stop or exception
-> (c -> e -> Stream m b -> m (Stream m b)) -- ^ on exception
-> (c -> Stream m b) -- ^ stream generator
-> Stream m b
gbracket bef exc aft gc fexc fnormal =
Stream step GBracketIOInit
where
-- If the stream is never evaluated the "aft" action will never be
-- called. For that to occur we will need the user of this API to pass a
-- weak pointer to us.
{-# INLINE_LATE step #-}
step _ GBracketIOInit = do
-- We mask asynchronous exceptions to make the execution
-- of 'bef' and the registration of 'aft' atomic.
-- A similar thing is done in the resourcet package: https://git.io/JvKV3
-- Tutorial: https://markkarpov.com/tutorial/exceptions.html
(r, ref) <- liftBaseOp_ mask_ $ do
r <- bef
ref <- newIOFinalizer (gc r)
return (r, ref)
return $ Skip $ GBracketIONormal (fnormal r) r ref
step gst (GBracketIONormal (UnStream step1 st) v ref) = do
res <- exc $ step1 gst st
case res of
Right r -> case r of
Yield x s ->
return $ Yield x (GBracketIONormal (Stream step1 s) v ref)
Skip s ->
return $ Skip (GBracketIONormal (Stream step1 s) v ref)
Stop ->
clearingIOFinalizer ref (aft v) >> return Stop
-- XXX Do not handle async exceptions, just rethrow them.
Left e -> do
-- Clearing of finalizer and running of exception handler must
-- be atomic wrt async exceptions. Otherwise if we have cleared
-- the finalizer and have not run the exception handler then we
-- may leak the resource.
stream <- clearingIOFinalizer ref (fexc v e (UnStream step1 st))
return $ Skip (GBracketIOException stream)
step gst (GBracketIOException (UnStream step1 st)) = do
res <- step1 gst st
case res of
Yield x s ->
return $ Yield x (GBracketIOException (Stream step1 s))
Skip s -> return $ Skip (GBracketIOException (Stream step1 s))
Stop -> return Stop
-- | See 'Streamly.Internal.Data.Stream.IsStream.before'.
--
{-# INLINE_NORMAL before #-}
before :: Monad m => m b -> Stream m a -> Stream m a
before action (Stream step state) = Stream step' Nothing
where
{-# INLINE_LATE step' #-}
step' _ Nothing = action >> return (Skip (Just state))
step' gst (Just st) = do
res <- step gst st
case res of
Yield x s -> return $ Yield x (Just s)
Skip s -> return $ Skip (Just s)
Stop -> return Stop
-- | See 'Streamly.Internal.Data.Stream.IsStream.after_'.
--
{-# INLINE_NORMAL after_ #-}
after_ :: Monad m => m b -> Stream m a -> Stream m a
after_ action (Stream step state) = Stream step' state
where
{-# INLINE_LATE step' #-}
step' gst st = do
res <- step gst st
case res of
Yield x s -> return $ Yield x s
Skip s -> return $ Skip s
Stop -> action >> return Stop
-- | See 'Streamly.Internal.Data.Stream.IsStream.after'.
--
{-# INLINE_NORMAL after #-}
after :: (MonadIO m, MonadBaseControl IO m)
=> m b -> Stream m a -> Stream m a
after action (Stream step state) = Stream step' Nothing
where
{-# INLINE_LATE step' #-}
step' _ Nothing = do
ref <- newIOFinalizer action
return $ Skip $ Just (state, ref)
step' gst (Just (st, ref)) = do
res <- step gst st
case res of
Yield x s -> return $ Yield x (Just (s, ref))
Skip s -> return $ Skip (Just (s, ref))
Stop -> do
runIOFinalizer ref
return Stop
-- XXX For high performance error checks in busy streams we may need another
-- Error constructor in step.
--
-- | See 'Streamly.Internal.Data.Stream.IsStream.onException'.
--
{-# INLINE_NORMAL onException #-}
onException :: MonadCatch m => m b -> Stream m a -> Stream m a
onException action str =
gbracket_ (return ()) (inline MC.try) return
(\_ (e :: MC.SomeException) _ -> nilM (action >> MC.throwM e))
(const str)
{-# INLINE_NORMAL _onException #-}
_onException :: MonadCatch m => m b -> Stream m a -> Stream m a
_onException action (Stream step state) = Stream step' state
where
{-# INLINE_LATE step' #-}
step' gst st = do
res <- step gst st `MC.onException` action
case res of
Yield x s -> return $ Yield x s
Skip s -> return $ Skip s
Stop -> return Stop
-- | See 'Streamly.Internal.Data.Stream.IsStream.bracket_'.
--
{-# INLINE_NORMAL bracket_ #-}
bracket_ :: MonadCatch m
=> m b -> (b -> m c) -> (b -> Stream m a) -> Stream m a
bracket_ bef aft =
gbracket_ bef (inline MC.try) aft
(\a (e :: SomeException) _ -> nilM (aft a >> MC.throwM e))
-- | See 'Streamly.Internal.Data.Stream.IsStream.bracket'.
--
{-# INLINE_NORMAL bracket' #-}
bracket' :: (MonadAsync m, MonadCatch m) =>
m b
-> (b -> m c)
-> (b -> m d)
-> (b -> m e)
-> (b -> Stream m a)
-> Stream m a
bracket' bef aft exc gc =
gbracket bef (inline MC.try) aft gc
(\a (e :: SomeException) _ -> exc a >> return (nilM (MC.throwM e)))
data BracketState s v = BracketInit | BracketRun s v
-- | Alternate (custom) implementation of 'bracket'.
--
{-# INLINE_NORMAL _bracket #-}
_bracket :: MonadCatch m
=> m b -> (b -> m c) -> (b -> Stream m a) -> Stream m a
_bracket bef aft bet = Stream step' BracketInit
where
{-# INLINE_LATE step' #-}
step' _ BracketInit = bef >>= \x -> return (Skip (BracketRun (bet x) x))
-- NOTE: It is important to use UnStream instead of the Stream pattern
-- here, otherwise we get huge perf degradation, see note in concatMap.
step' gst (BracketRun (UnStream step state) v) = do
-- res <- step gst state `MC.onException` aft v
res <- inline MC.try $ step gst state
case res of
Left (e :: SomeException) -> aft v >> MC.throwM e >> return Stop
Right r -> case r of
Yield x s -> return $ Yield x (BracketRun (Stream step s) v)
Skip s -> return $ Skip (BracketRun (Stream step s) v)
Stop -> aft v >> return Stop
-- | See 'Streamly.Internal.Data.Stream.IsStream.finally_'.
--
{-# INLINE finally_ #-}
finally_ :: MonadCatch m => m b -> Stream m a -> Stream m a
finally_ action xs = bracket_ (return ()) (const action) (const xs)
-- | See 'Streamly.Internal.Data.Stream.IsStream.finally'.
--
-- finally action xs = after action $ onException action xs
--
{-# INLINE finally #-}
finally :: (MonadAsync m, MonadCatch m) => m b -> Stream m a -> Stream m a
finally action xs = bracket' (return ()) act act act (const xs)
where act _ = action
-- | See 'Streamly.Internal.Data.Stream.IsStream.ghandle'.
--
{-# INLINE_NORMAL ghandle #-}
ghandle :: (MonadCatch m, Exception e)
=> (e -> Stream m a -> Stream m a) -> Stream m a -> Stream m a
ghandle f str =
gbracket_ (return ()) (inline MC.try) return (const f) (const str)
-- | See 'Streamly.Internal.Data.Stream.IsStream.handle'.
--
{-# INLINE_NORMAL handle #-}
handle :: (MonadCatch m, Exception e)
=> (e -> Stream m a) -> Stream m a -> Stream m a
handle f str =
gbracket_ (return ()) (inline MC.try) return (\_ e _ -> f e) (const str)
-- | Alternate (custom) implementation of 'handle'.
--
{-# INLINE_NORMAL _handle #-}
_handle :: (MonadCatch m, Exception e)
=> (e -> Stream m a) -> Stream m a -> Stream m a
_handle f (Stream step state) = Stream step' (Left state)
where
{-# INLINE_LATE step' #-}
step' gst (Left st) = do
res <- inline MC.try $ step gst st
case res of
Left e -> return $ Skip $ Right (f e)
Right r -> case r of
Yield x s -> return $ Yield x (Left s)
Skip s -> return $ Skip (Left s)
Stop -> return Stop
step' gst (Right (UnStream step1 st)) = do
res <- step1 gst st
case res of
Yield x s -> return $ Yield x (Right (Stream step1 s))
Skip s -> return $ Skip (Right (Stream step1 s))
Stop -> return Stop
data RetryState emap s1 s2
= RetryWithMap emap s1
| RetryDefault s2
-- | See 'Streamly.Internal.Data.Stream.IsStream.retry'
--
{-# INLINE_NORMAL retry #-}
retry
:: forall e m a. (Exception e, Ord e, MonadCatch m)
=> Map e Int
-- ^ map from exception to retry count
-> (e -> Stream m a)
-- ^ default handler for those exceptions that are not in the map
-> Stream m a
-> Stream m a
retry emap0 defaultHandler (Stream step0 state0) = Stream step state
where
state = RetryWithMap emap0 state0
{-# INLINE_LATE step #-}
step gst (RetryWithMap emap st) = do
eres <- MC.try $ step0 gst st
case eres of
Left e -> handler e emap st
Right res ->
return
$ case res of
Yield x st1 -> Yield x $ RetryWithMap emap st1
Skip st1 -> Skip $ RetryWithMap emap st1
Stop -> Stop
step gst (RetryDefault (UnStream step1 state1)) = do
res <- step1 gst state1
return
$ case res of
Yield x st1 -> Yield x $ RetryDefault (Stream step1 st1)
Skip st1 -> Skip $ RetryDefault (Stream step1 st1)
Stop -> Stop
{-# INLINE handler #-}
handler e emap st =
return
$ Skip
$ case Map.lookup e emap of
Just i
| i > 0 ->
let emap1 = Map.insert e (i - 1) emap
in RetryWithMap emap1 st
| otherwise -> RetryDefault $ defaultHandler e
Nothing -> RetryDefault $ defaultHandler e