Network.Remote.RPC

Declaration of the frontend for RPC.

Documentation

class Host a where

Host World declares that the world is a host. It should only have one constructor, and the location and port should be invariant of the given constructor. Specifically, getLocation and getPort should work even if bottom is supplied.

Methods

getLocation :: a -> String

getPort :: a -> Integer

getValue :: a

data WIO w m a

WIO w m a is a newtype over a server transformer that adds the phantom host argument w

Instances

(Sendable m a' a, Sendable m b b') => Sendable m (a -> b) (a' -> WIO w m b')

MonadTrans (WIO w)

Monad m => Monad (WIO w m)

Functor m => Functor (WIO w m)

MonadIO m => MonadIO (WIO w m)

Forkable m => Forkable (WIO w m)

Servable m => Servable (WIO w m)

(Host w, Servable m, Sendable m a a') => Service (WIO w m a) m w

(Sendable m' a a', Host w, Host w', Servable m, Servable m') => RPC (WIO w m a) (WIO w' m' a') m' w'

class (Functor m, Monad m, MonadIO m, Forkable m) => Servable m

Servable is a declaration that the given monad can be made into a servlet.

Instances

Servable IO

Servable m => Servable (AIO m)

Servable m => Servable (WIO w m)

liftIO :: MonadIO m => forall a. IO a -> m a

Lift a computation from the IO monad.

runServer :: forall w m. (Servable m, Host w) => WIO w m () -> m ()

runServer runs a name server and doesn't return

runServerBG :: Host w => WIO w IO () -> IO ThreadId

runServerBG runs a name server on a background thread and does return

onHost :: forall w m. (Servable m, Host w) => w -> WIO w m ()

onHost declares that the code is running on the given host. it is usefull when a type inference is wanted, but the action also needs to be made into a service and used as a remote procedure

autoService :: Name -> Q Exp

$(autoService 'World) finds all services declared in the module that definitely run on the given world, and makes them listen for incoming requests.

makeHost :: String -> String -> Integer -> Q [Dec]

$(makeHost "HostName" "hostLocation" hostPortNumber) makes a newtype HostName and declares an instance Host HostName.

makeServices :: [Name] -> Q Exp

$(makeServices ['service1 ,..., 'serviceN]) makes all given services listen for incoming requests.

rpcCall :: Name -> Q Exp

$(rpcCall 'serviceNm) simply splices in realRemoteCall (undefined :: typeofcall) "serviceNm" which is typed in a manner similar to typeofcall.

class Monad m => Forkable m where

Methods

forkIO :: m a -> m ThreadId

Instances

Forkable IO

Forkable m => Forkable (AIO m)

Forkable m => Forkable (ReaderT r m)

Forkable m => Forkable (WIO w m)

Example: Making remote Calls

This example shows how to make remote procedure from a Client to a Host. It also shows how to send functions, even though these will space leak.

-- LANGUAGE TemplateHaskell, KindSignatures, FlexibleContexts
module Main where
import Network.Remote.RPC

First, hosts must be declared. In the future, hosts might be declared in a configuration file such that they can be configured at runtime rather than only at compile time.

$(makeHost "Client" "localhost" 9000)
$(makeHost "Server" "localhost" 9001)

The following services will run on the server.

doubleServer :: Integer -> WIO Server IO Integer
doubleServer t = return $ t + t

addServer :: Integer -> WIO Server IO (Integer -> Integer)
addServer t = return (t +)

When used, addServer will return a function of type Integer -> WIO w IO Integer because the resulting function will actually be a remote call. Every time addServer is called, it turns the function into a permanent service. This should change in the future. For now, recognize that this can create a space leak if not used carefully.

client = do
  onHost Client
  double <- $(rpcCall 'doubleServer) 3
  liftIO $ putStrLn $ "r(h3+h3) ? " ++ show double
         
  add <- $(rpcCall 'addServer) 4
  r <- add 6 -- add :: Integer -> WIO Client IO Integer
  liftIO $ putStrLn $ "r(h4 +) h6 ? " ++ show r

Despite rpcCall being a template splice, the resulting splice is type safe:

 $(rpcCall 'doubleServer) :: (Host w, Servable m) => Integer -> WIO w m Integer

Now we declare the runtime. Usually this would be in two different mains, but for educational and testing purposes, both the client and server can be run from the same main.

main = do
  runServerBG $(autoService 'Server)
  runServer client

1. $(autoService 'Server) looks for services declared in the file which definitely run on server, and runs them as services on the intended host (Server in this case).
2. runServerBG runs a service server on a background OS thread, and returns
3. runServer runs a service server and does not return.
4. When run:

>>> :main
r(h3+h3) ? 6
r(h4 +) h6 ? 10

Where rVal means Val is on the server and hVal means Val is on the client.

class MonadTrans t where

The class of monad transformers. Instances should satisfy the following laws, which state that lift is a transformer of monads:

• lift . return = return

• lift (m >>= f) = lift m >>= (lift . f)

Methods

lift :: Monad m => m a -> t m a

Lift a computation from the argument monad to the constructed monad.

Instances

MonadTrans ListT

MonadTrans MaybeT

MonadTrans IdentityT

MonadTrans AIO

MonadTrans (ContT r)

Error e => MonadTrans (ErrorT e)

MonadTrans (ReaderT r)

MonadTrans (StateT s)

MonadTrans (StateT s)

Monoid w => MonadTrans (WriterT w)

Monoid w => MonadTrans (WriterT w)

MonadTrans (WIO w)

Monoid w => MonadTrans (RWST r w s)

Monoid w => MonadTrans (RWST r w s)