async

Run IO operations asynchronously and wait for their results

Version on this page:	2.2.1@rev:1
LTS Haskell 21.23:	2.2.5
Stackage Nightly 2023-12-07:	2.2.5
Latest on Hackage:	2.2.5

See all snapshots async appears in

BSD-3-Clause licensed by Simon Marlow

Maintained by Simon Marlow

This version can be pinned in stack with:async-2.2.1@sha256:61789382f449a02f827e70a029ba8f24a223b9c6b3792bb094fbd41ee360e851,2983

Module documentation for 2.2.1

Control
- Control.Concurrent
  - Control.Concurrent.Async

Depends on 4 packages(full list with versions):

async, base, hashable, stm

Used by 70 packages in lts-13.19(full list with versions):

This package provides a higher-level interface over threads, in which an Async a is a concurrent thread that will eventually deliver a value of type a. The package provides ways to create Async computations, wait for their results, and cancel them.

Using Async is safer than using threads in two ways:

When waiting for a thread to return a result, if the thread dies with an exception then the caller must either re-throw the exception (wait) or handle it (waitCatch); the exception cannot be ignored.
The API makes it possible to build a tree of threads that are automatically killed when their parent dies (see withAsync).

Changes

Changes in 2.2.1:

Add a Hashable instance for Async
Bump upper bounds
Documentation updates

Changes in 2.2:

cancel now throws AsyncCancelled instead of ThreadKilled
link and link2 now wrap exceptions in ExceptionInLinkedThread when throwing to the linked thread. ExceptionInLinkedThread is a child of AsyncException in the exception hierarchy, so this maintains the invariant that exceptions thrown asynchronously should be AsyncExceptions.
link and link2 do not propagate AsyncCancelled, so it’s now possible to cancel a linked thread without cancelling yourself.
Added linkOnly and link2Only to specify which exceptions should be propagated,if you want something other than the default behaviour of ignoring AsyncCancelled.
new utility function compareAsyncs for comparing Asyncs of different types.
Add a Hashable instance for Async a

Changes in 2.1.1.1:

Make ‘cancelWith’ wait for the cancelled thread to terminate, like ‘cancel’
Updates to dependency bounds for GHC 8.2

Changes in 2.1.1:

Add concurrently_
Add replicateConcurrently
Add replicateConcurrently_
Fix incorrect argument order in forConcurrently_
Generalize mapConcurrently_ and forConcurrently_ to Foldable
withAsync now reliably kills the thread, by using an uninterruptible cancel
Make cancel wait for the thread to finish, and adjust ‘concurrently’ to match

Changes in 2.1.0:

Bump base dependency to allow 4.10
Remove invalid Monad instance for Concurrently
Add Monoid and Semigroup instances for Concurrently
Add forConcurrently (flipped version of mapConcurrently)
Add STM version of all applicable IO functions: waitAnySTM, waitAnyCatchSTM, waitEitherSTM, waitEitherCatchSTM, waitEitherSTM_, and waitBothSTM.

Changes in 2.0.2:

Add a Monad instance for Concurrently
Bump base dependency to allow 4.9

Changes in 2.0.1.6:

Add workaround to waitCatch for #14

Changes in 2.0.1.5:

Bump base dependencies for GHC 7.8

Changes in 2.0.1.4:

Bump base dependency of test suite

Changes in 2.0.1.3:

Bump base dependency to allow 4.6

Changes in 2.0.1.2:

Bump stm dependency to 2.4

Changes in 2.0.1.1:

Safe Haskell support: Control.Concurrent.Async is now Trustworthy

Changes in 2.0.1.0:

Added a Functor instance for Async
Added asyncBound, asyncOn, asyncWithUnmask, asyncOnWithUnmask, withAsyncBound, withAsyncOn, withAsyncWithUnmask, withAsyncOnWithUnmask.
Added mapConcurrently
Added Concurrently (with Applicative and Alternative instances)