UnliftIO.Async

Unlifted Control.Concurrent.Async.

Since: 0.1.0.0

Asynchronous actions

data Async a

An asynchronous action spawned by async or withAsync. Asynchronous actions are executed in a separate thread, and operations are provided for waiting for asynchronous actions to complete and obtaining their results (see e.g. wait).

Instances

Functor Async

Defined in Control.Concurrent.Async

Methods

fmap :: (a -> b) -> Async a -> Async b

(<$) :: a -> Async b -> Async a

Eq (Async a)

Defined in Control.Concurrent.Async

Methods

(==) :: Async a -> Async a -> Bool

(/=) :: Async a -> Async a -> Bool

Ord (Async a)

Defined in Control.Concurrent.Async

Methods

compare :: Async a -> Async a -> Ordering

(<) :: Async a -> Async a -> Bool

(<=) :: Async a -> Async a -> Bool

(>) :: Async a -> Async a -> Bool

(>=) :: Async a -> Async a -> Bool

max :: Async a -> Async a -> Async a

min :: Async a -> Async a -> Async a

Hashable (Async a)

Defined in Control.Concurrent.Async

Methods

hashWithSalt :: Int -> Async a -> Int

hash :: Async a -> Int

Spawning

async :: MonadUnliftIO m => m a -> m (Async a)

Unlifted async.

Since: 0.1.0.0

asyncBound :: MonadUnliftIO m => m a -> m (Async a)

Unlifted asyncBound.

Since: 0.1.0.0

asyncOn :: MonadUnliftIO m => Int -> m a -> m (Async a)

Unlifted asyncOn.

Since: 0.1.0.0

asyncWithUnmask :: MonadUnliftIO m => ((forall b. m b -> m b) -> m a) -> m (Async a)

Unlifted asyncWithUnmask.

Since: 0.1.0.0

asyncOnWithUnmask :: MonadUnliftIO m => Int -> ((forall b. m b -> m b) -> m a) -> m (Async a)

Unlifted asyncOnWithUnmask.

Since: 0.1.0.0

Spawning with automatic cancelation

withAsync :: MonadUnliftIO m => m a -> (Async a -> m b) -> m b

Unlifted withAsync.

Since: 0.1.0.0

withAsyncBound :: MonadUnliftIO m => m a -> (Async a -> m b) -> m b

Unlifted withAsyncBound.

Since: 0.1.0.0

withAsyncOn :: MonadUnliftIO m => Int -> m a -> (Async a -> m b) -> m b

Unlifted withAsyncOn.

Since: 0.1.0.0

withAsyncWithUnmask :: MonadUnliftIO m => ((forall c. m c -> m c) -> m a) -> (Async a -> m b) -> m b

Unlifted withAsyncWithUnmask.

Since: 0.1.0.0

withAsyncOnWithUnmask :: MonadUnliftIO m => Int -> ((forall c. m c -> m c) -> m a) -> (Async a -> m b) -> m b

Unlifted withAsyncOnWithMask.

Since: 0.1.0.0

Querying Asyncs

wait :: MonadIO m => Async a -> m a

Lifted wait.

Since: 0.1.0.0

poll :: MonadIO m => Async a -> m (Maybe (Either SomeException a))

Lifted poll.

Since: 0.1.0.0

waitCatch :: MonadIO m => Async a -> m (Either SomeException a)

Lifted waitCatch.

Since: 0.1.0.0

cancel :: MonadIO m => Async a -> m ()

Lifted cancel.

Since: 0.1.0.0

uninterruptibleCancel :: MonadIO m => Async a -> m ()

Lifted uninterruptibleCancel.

Since: 0.1.0.0

cancelWith :: (Exception e, MonadIO m) => Async a -> e -> m ()

Lifted cancelWith. Additionally uses toAsyncException to ensure async exception safety.

Since: 0.1.0.0

asyncThreadId :: Async a -> ThreadId

Returns the ThreadId of the thread running the given Async.

STM operations

waitSTM :: Async a -> STM a

A version of wait that can be used inside an STM transaction.

pollSTM :: Async a -> STM (Maybe (Either SomeException a))

A version of poll that can be used inside an STM transaction.

waitCatchSTM :: Async a -> STM (Either SomeException a)

A version of waitCatch that can be used inside an STM transaction.

Waiting for multiple Asyncs

waitAny :: MonadIO m => [Async a] -> m (Async a, a)

Lifted waitAny.

Since: 0.1.0.0

waitAnyCatch :: MonadIO m => [Async a] -> m (Async a, Either SomeException a)

Lifted waitAnyCatch.

Since: 0.1.0.0

waitAnyCancel :: MonadIO m => [Async a] -> m (Async a, a)

Lifted waitAnyCancel.

Since: 0.1.0.0

waitAnyCatchCancel :: MonadIO m => [Async a] -> m (Async a, Either SomeException a)

Lifted waitAnyCatchCancel.

Since: 0.1.0.0

waitEither :: MonadIO m => Async a -> Async b -> m (Either a b)

Lifted waitEither.

Since: 0.1.0.0

waitEitherCatch :: MonadIO m => Async a -> Async b -> m (Either (Either SomeException a) (Either SomeException b))

Lifted waitEitherCatch.

Since: 0.1.0.0

waitEitherCancel :: MonadIO m => Async a -> Async b -> m (Either a b)

Lifted waitEitherCancel.

Since: 0.1.0.0

waitEitherCatchCancel :: MonadIO m => Async a -> Async b -> m (Either (Either SomeException a) (Either SomeException b))

Lifted waitEitherCatchCancel.

Since: 0.1.0.0

waitEither_ :: MonadIO m => Async a -> Async b -> m ()

Lifted waitEither_.

Since: 0.1.0.0

waitBoth :: MonadIO m => Async a -> Async b -> m (a, b)

Lifted waitBoth.

Since: 0.1.0.0

Waiting for multiple Asyncs in STM

waitAnySTM :: [Async a] -> STM (Async a, a)

A version of waitAny that can be used inside an STM transaction.

Since: async-2.1.0

waitAnyCatchSTM :: [Async a] -> STM (Async a, Either SomeException a)

A version of waitAnyCatch that can be used inside an STM transaction.

Since: async-2.1.0

waitEitherSTM :: Async a -> Async b -> STM (Either a b)

A version of waitEither that can be used inside an STM transaction.

Since: async-2.1.0

waitEitherCatchSTM :: Async a -> Async b -> STM (Either (Either SomeException a) (Either SomeException b))

A version of waitEitherCatch that can be used inside an STM transaction.

Since: async-2.1.0

waitEitherSTM_ :: Async a -> Async b -> STM ()

A version of waitEither_ that can be used inside an STM transaction.

Since: async-2.1.0

waitBothSTM :: Async a -> Async b -> STM (a, b)

A version of waitBoth that can be used inside an STM transaction.

Since: async-2.1.0

Linking

link :: MonadIO m => Async a -> m ()

Lifted link.

Since: 0.1.0.0

link2 :: MonadIO m => Async a -> Async b -> m ()

Lifted link2.

Since: 0.1.0.0

Pooled concurrency

pooledMapConcurrentlyN

Arguments

:: (MonadUnliftIO m, Traversable t)

=> Int

Max. number of threads. Should not be less than 1.

-> (a -> m b)

-> t a

-> m (t b)

Like mapConcurrently from async, but instead of one thread per element, it does pooling from a set of threads. This is useful in scenarios where resource consumption is bounded and for use cases where too many concurrent tasks aren't allowed.

Example usage

import Say

action :: Int -> IO Int
action n = do
  tid <- myThreadId
  sayString $ show tid
  threadDelay (2 * 10^6) -- 2 seconds
  return n

main :: IO ()
main = do
  yx <- pooledMapConcurrentlyN 5 (\x -> action x) [1..5]
  print yx

On executing you can see that five threads have been spawned:

$ ./pool
ThreadId 36
ThreadId 38
ThreadId 40
ThreadId 42
ThreadId 44
[1,2,3,4,5]

Let's modify the above program such that there are less threads than the number of items in the list:

import Say

action :: Int -> IO Int
action n = do
  tid <- myThreadId
  sayString $ show tid
  threadDelay (2 * 10^6) -- 2 seconds
  return n

main :: IO ()
main = do
  yx <- pooledMapConcurrentlyN 3 (\x -> action x) [1..5]
  print yx

On executing you can see that only three threads are active totally:

$ ./pool
ThreadId 35
ThreadId 37
ThreadId 39
ThreadId 35
ThreadId 39
[1,2,3,4,5]

Since: 0.2.10

pooledMapConcurrently :: (MonadUnliftIO m, Traversable t) => (a -> m b) -> t a -> m (t b)

Similar to pooledMapConcurrentlyN but with number of threads set from getNumCapabilities. Usually this is useful for CPU bound tasks.

Since: 0.2.10

pooledMapConcurrentlyN_

Arguments

:: (MonadUnliftIO m, Foldable f)

=> Int

Max. number of threads. Should not be less than 1.

-> (a -> m b)

-> f a

-> m ()

Like pooledMapConcurrentlyN but with the return value discarded.

Since: 0.2.10

pooledMapConcurrently_ :: (MonadUnliftIO m, Foldable f) => (a -> m b) -> f a -> m ()

Like pooledMapConcurrently but with the return value discarded.

Since: 0.2.10

pooledForConcurrentlyN

Arguments

:: (MonadUnliftIO m, Traversable t)

=> Int

Max. number of threads. Should not be less than 1.

-> t a

-> (a -> m b)

-> m (t b)

Similar to pooledMapConcurrentlyN but with flipped arguments.

Since: 0.2.10

pooledForConcurrently :: (MonadUnliftIO m, Traversable t) => t a -> (a -> m b) -> m (t b)

Similar to pooledForConcurrentlyN but with number of threads set from getNumCapabilities. Usually this is useful for CPU bound tasks.

Since: 0.2.10

pooledForConcurrentlyN_

Arguments

:: (MonadUnliftIO m, Foldable t)

=> Int

Max. number of threads. Should not be less than 1.

-> t a

-> (a -> m b)

-> m ()

Like pooledMapConcurrentlyN_ but with flipped arguments.

Since: 0.2.10

pooledForConcurrently_ :: (MonadUnliftIO m, Foldable f) => f a -> (a -> m b) -> m ()

Like pooledMapConcurrently_ but with flipped arguments.

Since: 0.2.10

pooledReplicateConcurrentlyN

Arguments

:: MonadUnliftIO m

=> Int

Max. number of threads. Should not be less than 1.

-> Int

Number of times to perform the action.

-> m a

-> m [a]

Pooled version of replicateConcurrently. Performs the action in the pooled threads.

Since: 0.2.10

pooledReplicateConcurrently

Arguments

:: MonadUnliftIO m

=> Int

Number of times to perform the action.

-> m a

-> m [a]

Similar to pooledReplicateConcurrentlyN but with number of threads set from getNumCapabilities. Usually this is useful for CPU bound tasks.

Since: 0.2.10

pooledReplicateConcurrentlyN_

Arguments

:: MonadUnliftIO m

=> Int

Max. number of threads. Should not be less than 1.

-> Int

Number of times to perform the action.

-> m a

-> m ()

Pooled version of replicateConcurrently_. Performs the action in the pooled threads.

Since: 0.2.10

pooledReplicateConcurrently_

Arguments

:: MonadUnliftIO m

=> Int

Number of times to perform the action.

-> m a

-> m ()

Similar to pooledReplicateConcurrently_ but with number of threads set from getNumCapabilities. Usually this is useful for CPU bound tasks.

Since: 0.2.10

Convenient utilities

race :: MonadUnliftIO m => m a -> m b -> m (Either a b)

Unlifted race.

Since: 0.1.0.0

race_ :: MonadUnliftIO m => m a -> m b -> m ()

Unlifted race_.

Since: 0.1.0.0

concurrently :: MonadUnliftIO m => m a -> m b -> m (a, b)

Unlifted concurrently.

Since: 0.1.0.0

concurrently_ :: MonadUnliftIO m => m a -> m b -> m ()

Unlifted concurrently_.

Since: 0.1.0.0

mapConcurrently :: MonadUnliftIO m => Traversable t => (a -> m b) -> t a -> m (t b)

Executes a Traversable container of items concurrently, it uses the Flat type internally.

Since: 0.1.0.0

forConcurrently :: MonadUnliftIO m => Traversable t => t a -> (a -> m b) -> m (t b)

Similar to mapConcurrently but with arguments flipped

Since: 0.1.0.0

mapConcurrently_ :: MonadUnliftIO m => Foldable f => (a -> m b) -> f a -> m ()

Executes a Traversable container of items concurrently, it uses the Flat type internally. This function ignores the results.

Since: 0.1.0.0

forConcurrently_ :: MonadUnliftIO m => Foldable f => f a -> (a -> m b) -> m ()

Similar to mapConcurrently_ but with arguments flipped

Since: 0.1.0.0

replicateConcurrently :: MonadUnliftIO m => Int -> m b -> m [b]

Unlifted replicateConcurrently.

Since: 0.1.0.0

replicateConcurrently_ :: (Applicative m, MonadUnliftIO m) => Int -> m a -> m ()

Unlifted replicateConcurrently_.

Since: 0.1.0.0

newtype Concurrently m a

Unlifted Concurrently.

Since: 0.1.0.0

Constructors

Concurrently

Fields

• runConcurrently :: m a

Instances

Monad m => Functor (Concurrently m)

Since: 0.1.0.0

Defined in UnliftIO.Internals.Async

Methods

fmap :: (a -> b) -> Concurrently m a -> Concurrently m b

(<$) :: a -> Concurrently m b -> Concurrently m a

MonadUnliftIO m => Applicative (Concurrently m)

Since: 0.1.0.0

Defined in UnliftIO.Internals.Async

Methods

pure :: a -> Concurrently m a

(<*>) :: Concurrently m (a -> b) -> Concurrently m a -> Concurrently m b

liftA2 :: (a -> b -> c) -> Concurrently m a -> Concurrently m b -> Concurrently m c

(*>) :: Concurrently m a -> Concurrently m b -> Concurrently m b

(<*) :: Concurrently m a -> Concurrently m b -> Concurrently m a

MonadUnliftIO m => Alternative (Concurrently m)

Composing two unlifted Concurrently values using Alternative is the equivalent to using a race combinator, the asynchrounous sub-routine that returns a value first is the one that gets it's value returned, the slowest sub-routine gets cancelled and it's thread is killed.

Since: 0.1.0.0

Defined in UnliftIO.Internals.Async

Methods

empty :: Concurrently m a

(<|>) :: Concurrently m a -> Concurrently m a -> Concurrently m a

some :: Concurrently m a -> Concurrently m [a]

many :: Concurrently m a -> Concurrently m [a]

(MonadUnliftIO m, Semigroup a) => Semigroup (Concurrently m a)

Only defined by async for base >= 4.9.

Since: 0.1.0.0

Defined in UnliftIO.Internals.Async

Methods

(<>) :: Concurrently m a -> Concurrently m a -> Concurrently m a

sconcat :: NonEmpty (Concurrently m a) -> Concurrently m a

stimes :: Integral b => b -> Concurrently m a -> Concurrently m a

(Semigroup a, Monoid a, MonadUnliftIO m) => Monoid (Concurrently m a)

Since: 0.1.0.0

Defined in UnliftIO.Internals.Async

Methods

mempty :: Concurrently m a

mappend :: Concurrently m a -> Concurrently m a -> Concurrently m a

mconcat :: [Concurrently m a] -> Concurrently m a

data Conc m a

A more efficient alternative to Concurrently, which reduces the number of threads that need to be forked. For more information, see this blog post. This is provided as a separate type to Concurrently as it has a slightly different API.

Use the conc function to construct values of type Conc, and runConc to execute the composed actions. You can use the Applicative instance to run different actions and wait for all of them to complete, or the Alternative instance to wait for the first thread to complete.

In the event of a runtime exception thrown by any of the children threads, or an asynchronous exception received in the parent thread, all threads will be killed with an AsyncCancelled exception and the original exception rethrown. If multiple exceptions are generated by different threads, there are no guarantees on which exception will end up getting rethrown.

For many common use cases, you may prefer using helper functions in this module like mapConcurrently.

There are some intentional differences in behavior to Concurrently:

• Children threads are always launched in an unmasked state, not the inherited state of the parent thread.

Note that it is a programmer error to use the Alternative instance in such a way that there are no alternatives to an empty, e.g. runConc (empty | empty). In such a case, a ConcException will be thrown. If there was an Alternative in the standard libraries without empty, this library would use it instead.

Since: 0.2.9.0

Instances

Functor m => Functor (Conc m)

Defined in UnliftIO.Internals.Async

Methods

fmap :: (a -> b) -> Conc m a -> Conc m b

(<$) :: a -> Conc m b -> Conc m a

MonadUnliftIO m => Applicative (Conc m)

Since: 0.2.9.0

Defined in UnliftIO.Internals.Async

Methods

pure :: a -> Conc m a

(<*>) :: Conc m (a -> b) -> Conc m a -> Conc m b

liftA2 :: (a -> b -> c) -> Conc m a -> Conc m b -> Conc m c

(*>) :: Conc m a -> Conc m b -> Conc m b

(<*) :: Conc m a -> Conc m b -> Conc m a

MonadUnliftIO m => Alternative (Conc m)

Since: 0.2.9.0

Defined in UnliftIO.Internals.Async

Methods

empty :: Conc m a

(<|>) :: Conc m a -> Conc m a -> Conc m a

some :: Conc m a -> Conc m [a]

many :: Conc m a -> Conc m [a]

(MonadUnliftIO m, Semigroup a) => Semigroup (Conc m a)

Since: 0.2.9.0

Defined in UnliftIO.Internals.Async

Methods

(<>) :: Conc m a -> Conc m a -> Conc m a

sconcat :: NonEmpty (Conc m a) -> Conc m a

stimes :: Integral b => b -> Conc m a -> Conc m a

(Monoid a, MonadUnliftIO m) => Monoid (Conc m a)

Since: 0.2.9.0

Defined in UnliftIO.Internals.Async

Methods

mempty :: Conc m a

mappend :: Conc m a -> Conc m a -> Conc m a

mconcat :: [Conc m a] -> Conc m a

conc :: m a -> Conc m a

Construct a value of type Conc from an action. Compose these values using the typeclass instances (most commonly Applicative and Alternative) and then run with runConc.

Since: 0.2.9.0

runConc :: MonadUnliftIO m => Conc m a -> m a

Run a Conc value on multiple threads.

Since: 0.2.9.0

data ConcException

Things that can go wrong in the structure of a Conc. These are programmer errors.

Since: 0.2.9.0

Constructors

EmptyWithNoAlternative

Instances

Eq ConcException

Defined in UnliftIO.Internals.Async

Methods

(==) :: ConcException -> ConcException -> Bool

(/=) :: ConcException -> ConcException -> Bool

Ord ConcException

Defined in UnliftIO.Internals.Async

Methods

compare :: ConcException -> ConcException -> Ordering

(<) :: ConcException -> ConcException -> Bool

(<=) :: ConcException -> ConcException -> Bool

(>) :: ConcException -> ConcException -> Bool

(>=) :: ConcException -> ConcException -> Bool

max :: ConcException -> ConcException -> ConcException

min :: ConcException -> ConcException -> ConcException

Show ConcException

Defined in UnliftIO.Internals.Async

Methods

showsPrec :: Int -> ConcException -> ShowS

show :: ConcException -> String

showList :: [ConcException] -> ShowS

Generic ConcException

Defined in UnliftIO.Internals.Async

Associated Types

type Rep ConcException :: Type -> Type

Methods

from :: ConcException -> Rep ConcException x

to :: Rep ConcException x -> ConcException

Exception ConcException

Defined in UnliftIO.Internals.Async

Methods

toException :: ConcException -> SomeException

fromException :: SomeException -> Maybe ConcException

displayException :: ConcException -> String

type Rep ConcException

Defined in UnliftIO.Internals.Async

type Rep ConcException = D1 ('MetaData "ConcException" "UnliftIO.Internals.Async" "unliftio-0.2.14-DQLoqTgtkN4BuWCDtA8qoF" 'False) (C1 ('MetaCons "EmptyWithNoAlternative" 'PrefixI 'False) (U1 :: Type -> Type))