Safe Haskell	None
Language	Haskell2010

Control.Eff.Concurrent.Process.ForkIOScheduler

Description

Implement Erlang style message passing concurrency.

This handles the MessagePassing and Process effects, using TQueues and forkIO.

This aims to be a pragmatic implementation, so even logging is supported.

At the core is a main process that enters schedule and creates all of the internal state stored in TVars to manage processes with message queues.

The Eff handler for Process and MessagePassing use are implemented and available through spawn.

spawn uses forkFinally and TQueues and tries to catch most exceptions.

Synopsis

schedule :: Eff (ConsProcess SchedulerIO) () -> LogChannel LogMessage -> IO ()
defaultMain :: Eff (ConsProcess SchedulerIO) () -> IO ()
defaultMainWithLogChannel :: LogChannel LogMessage -> Eff (ConsProcess SchedulerIO) () -> IO ()
data SchedulerError
type SchedulerIO = '[Reader SchedulerVar, Logs LogMessage, Lift IO]
forkIoScheduler :: SchedulerProxy SchedulerIO
type HasSchedulerIO r = (HasCallStack, SetMember Lift (Lift IO) r, Member (Logs LogMessage) r, Member (Reader SchedulerVar) r)

Documentation

schedule :: Eff (ConsProcess SchedulerIO) () -> LogChannel LogMessage -> IO () Source #

This is the main entry point to running a message passing concurrency application. This function takes a Process on top of the SchedulerIO effect and a LogChannel for concurrent logging.

defaultMain :: Eff (ConsProcess SchedulerIO) () -> IO () Source #

Start the message passing concurrency system then execute a Process on top of SchedulerIO effect. All logging is sent to standard output.

defaultMainWithLogChannel :: LogChannel LogMessage -> Eff (ConsProcess SchedulerIO) () -> IO () Source #

Start the message passing concurrency system then execute a Process on top of SchedulerIO effect. All logging is sent to standard output.

data SchedulerError Source #

A sum-type with errors that can occur when scheduleing messages.

Constructors

ProcessNotFound ProcessId	No process info was found for a `ProcessId` during internal processing. NOTE: This is ONLY caused by internal errors, probably by an incorrect `MessagePassing` handler in this module. Sending a message to a process ALWAYS succeeds! Even if the process does not exist.
ProcessRaisedError String	A process called `raiseError`.
ProcessExitError String	A process called `exitWithError`.
ProcessShuttingDown	A process exits.
SchedulerShuttingDown	An action was not performed while the scheduler was exiting.

Instances

Show SchedulerError Source #
Instance details Defined in Control.Eff.Concurrent.Process.ForkIOScheduler Methods showsPrec :: Int -> SchedulerError -> ShowS # show :: SchedulerError -> String # showList :: [SchedulerError] -> ShowS #
Exception SchedulerError Source #
Instance details Defined in Control.Eff.Concurrent.Process.ForkIOScheduler Methods toException :: SchedulerError -> SomeException # fromException :: SomeException -> Maybe SchedulerError # displayException :: SchedulerError -> String #

type SchedulerIO = '[Reader SchedulerVar, Logs LogMessage, Lift IO] Source #

The concrete list of Effects for this scheduler implementation. See HasSchedulerIO

forkIoScheduler :: SchedulerProxy SchedulerIO Source #

A SchedulerProxy for SchedulerIO

type HasSchedulerIO r = (HasCallStack, SetMember Lift (Lift IO) r, Member (Logs LogMessage) r, Member (Reader SchedulerVar) r) Source #

An alias for the constraints for the effects essential to this scheduler implementation, i.e. these effects allow spawning new Processes. See SchedulerIO