concurrent-rpc
==============
[![Available on Hackage][badge-hackage]][hackage]
[![License MIT][badge-license]][license]
[![Build Status][badge-travis]][travis]
### Summary
This library is small wrapper around `Control.Concurrent.MVar.MVar`s that can
be used to implement request-response communication between different threads.
### Example
```haskell
module MissileLauncher where
import Control.Exception
import Control.Monad
import Control.Concurrent
import Control.Concurrent.Async
import Control.Concurrent.RPC
import Data.Word
import System.Random
type Missile = Word
type LaunchSite = String
main :: IO ()
main = do
(launchMissile, withMissile) <- newRPC
runMissileProduction launchMissile
`race_` runLaunchSite withMissile "Redmond"
`race_` runLaunchSite withMissile "Cambridge"
runLaunchSite :: WithRPC Missile LaunchSite -> LaunchSite -> IO ()
runLaunchSite withMissile site = forever $ do
sleepRandom
catch
( withMissile $ \missile-> do
r <- random100
if r < 10
then error $ "bad weather in " ++ site
else do
printThread $ site ++ ": LAUNCH THE MISSILE!"
return site
)
( \e-> do
let _ = e :: SomeException
printThread $ site ++ ": Couldn't launch. Waiting for next missile."
)
runMissileProduction :: RPC Missile LaunchSite -> IO ()
runMissileProduction launchMissile =
produce `race_` produce `race_` produce `race_` produce
where
produce = forever $ do
sleepRandom
missile <- randomIO :: IO Missile
catch
( do
printThread $ "Production: Ready to launch missile " ++ show missile
site <- launchMissile missile
printThread $ "Production: Missile " ++ show missile ++ " launched in " ++ site
)
( \e->
printThread $ "Production: Missile " ++ show missile ++
" failed to launch due to " ++ show (e :: SomeException)
)
printThread :: Show a => a -> IO ()
printThread x = do
threadId <- myThreadId
random100 >>= \x-> threadDelay (x * 100)
putStrLn $ show threadId ++ ": " ++ show x
random100 :: IO Int
random100 = (`mod` 100) <$> randomIO
sleepRandom :: IO ()
sleepRandom = random100 >>= \x-> threadDelay (x * 100000)
```
### Dependencies
- base >= 4.7 && < 5
[badge-travis]: https://img.shields.io/travis/lpeterse/haskell-concurrent-rpc.svg
[travis]: https://travis-ci.org/lpeterse/haskell-concurrent-rpc
[badge-hackage]: https://img.shields.io/hackage/v/concurrent-rpc.svg?dummy
[hackage]: https://hackage.haskell.org/package/concurrent-rpc
[badge-license]: https://img.shields.io/badge/license-MIT-green.svg?dummy
[license]: https://github.com/lpeterse/haskell-concurrent-rpc/blob/master/LICENSE
[issues]: https://github.com/lpeterse/haskell-concurrent-rpc/issues
[Github]: https://github.com/lpeterse/haskell-concurrent-rpc