websockets-rpc

A simple message-based streaming RPC mechanism built using WebSockets

Usage

The idea is pretty simple:

• A client initiates the RPC call to a server with a Subscription
• the client may send additional data at any time with Supply, who can also cancel the RPC call
• the server may respond incrementally with Reply
• the server finishes the RPC call with a Complete

client server ------------------------subscribe---------------------------> - - - - - - - - - - - - -supply - - - - - - - - - - - - - - > < - - - - - - - - - - - -reply- - - - - - - - - - - - - - - - <-----------------------complete----------------------------- 

if the supply and reply parts were ommitted, it would be identical to a traditional RPC mechanism.

Example

import Network.WebSockets.RPC import Data.Aeson -- subscriptions from client to server data MySubDSL = Foo deriving (FromJSON, ToJSON) -- you should figure this part out :) -- supplies from client to server data MySupDSL = Bar deriving (FromJSON, ToJSON) -- replies from server to client data MyRepDSL = Baz deriving (FromJSON, ToJSON) -- onCompletes from server to client data MyComDSL = Qux deriving (FromJSON, ToJSON) 

Server:

{-# LANGUAGE NamedFieldPuns, ScopedTypeVariables #-} myServer :: (MonadIO m, MonadThrow m) => ServerAppT (WebSocketServerRPCT MySubDSL MySupDSL m) myServer = rpcServer $ \RPCServerParams{reply,complete} eSubSup -> case eSubSup of Left Foo -> do forM_ [1..5] $ \_ -> do liftIO $ threadDelay 1000000 reply Baz complete Qux Right Bar -> reply Baz 

Client:

{-# LANGUAGE NamedFieldPuns #-} myClient :: (MonadIO m, MonadThrow m) => ClientAppT (WebSocketClientRPCT MyRepDSL MyComDSL m) () myClient = rpcClient $ \dispatch -> -- only going to make one RPC call for this example dispatch RPCClient { subscription = Foo , onReply = \RPCClientParams{supply,cancel} Baz -> do liftIO $ threadDelay 1000000 supply Bar (q :: Bool) <- liftIO getRandom if q then cancel else pure () , onComplete = \Qux -> liftIO $ putStrLn "finished" } 

the threadDelay calls are just to exemplify the asynchronisity of the system, nothing to do with avoiding race conditions >.>

To turn the ServerAppT and ClientAppT into natural WebSockets types, use the morphisms from Wai-Transformers.

Contributing

this is my swamp