Modulecabal-install-3.18.1.0Haskell2010

Distribution.Client.JobControl

A job control concurrency abstraction

3 types
16 values

Packagecabal-install-3.18.1.0
Exports19
LanguageHaskell2010
LicenceBSD-3-Clause
SourceJobControl.hs

datadata JobControl (m :: Type -> Type) a

A simple concurrency abstraction. Jobs can be spawned and can complete in any order. This allows both serial and parallel implementations.

valuenewSerialJobControl :: IO (JobControl IO a)

Make a JobControl that executes all jobs serially and in order. It only executes jobs on demand when they are collected, not eagerly.

Cancelling will cancel all jobs that have not been collected yet.

valuenewParallelJobControl :: WithCallStack (Int -> IO (JobControl IO a))

Make a JobControl that eagerly executes jobs in parallel, with a given maximum degree of parallelism.

Cancelling will cancel jobs that have not yet begun executing, but jobs that have already been executed or are currently executing cannot be cancelled.

valuenewSemaphoreJobControl :: WithCallStack (Verbosity -> Int -> IO (JobControl IO a))

Make a JobControl where the parallelism is controlled by a semaphore.

This uses the GHC -jsem option to allow GHC to take additional semaphore slots if we are not using them all.

valuespawnJob :: JobControl m a -> m a -> m ()

Add a new job to the pool of jobs

valuecollectJob :: JobControl m a -> m a

Wait until one job is complete

valueremainingJobs :: JobControl m a -> m Bool

Returns True if there are any outstanding jobs (ie spawned but yet to be collected)

valuecancelJobs :: JobControl m a -> m ()

Try to cancel any outstanding but not-yet-started jobs. Call remainingJobs after this to find out if any jobs are left (ie could not be cancelled).

valuecleanupJobControl :: JobControl m a -> m ()

cleanup any resources created by the JobControl, intended to be used as the finaliser for bracket.

valuejobControlSemaphore :: JobControl m a -> Maybe SemaphoreIdentifier

Identifier of the semaphore which can be used to control parallelism, if one is available for that job control type.

datadata JobLimit

valuenewJobLimit :: Int -> IO JobLimit

valuewithJobLimit :: JobLimit -> IO a -> IO a

newtypenewtype Lock

valuenewLock :: IO Lock

valuecriticalSection :: Lock -> IO a -> IO a

Higher level utils

3 declarations

valuenewJobControlFromParStrat

:: Verbosity
-> Maybe Compiler
The compiler, used to determine whether Jsem is supported. When Nothing, Jsem is assumed to be unsupported.
-> ParStratInstall
The parallel strategy
-> Maybe Int
A cap on the number of jobs (e.g. to force a maximum of 2 concurrent downloads despite a -j8 parallel strategy)
-> IO (JobControl IO a)

valuewithJobControl :: IO (JobControl IO a) -> (JobControl IO a -> IO b) -> IO b

valuemapConcurrentWithJobs :: JobControl IO b -> (a -> IO b) -> [a] -> IO [b]

Concurrently execute actions on a list using the given JobControl. The maximum number of concurrent jobs is tied to the JobControl instance. The resulting list does not preserve the original order!