{-# LANGUAGE OverloadedStrings #-}
-- Task worker - design 2
-- Adds pub-sub flow to receive and respond to kill signal
module Main where
import Control.Concurrent
import Control.Monad
import qualified Data.ByteString.Char8 as BS
import Data.Function
import System.IO
import System.ZMQ4.Monadic
import Text.Printf
main :: IO ()
main = runZMQ $ do
-- Socket to receive messages on
receiver <- socket Pull
connect receiver "tcp://localhost:5557"
-- Socket to send messages to
sender <- socket Push
connect sender "tcp://localhost:5558"
controller <- socket Sub
connect controller "tcp://localhost:5559"
subscribe controller ""
liftIO $ hSetBuffering stdout NoBuffering
fix $ \loop -> do
[receiver_events, controller_events] <-
poll (-1) [ Sock receiver [In] Nothing
, Sock controller [In] Nothing
]
when (receiver_events /= []) $ do
string <- BS.unpack <$> receive receiver
liftIO $ printf "%s." string -- Show the progress
liftIO $ threadDelay (read string * 1000) -- Do the work
send sender [] "" -- Send results to sink
-- Any waiting controller command acts as 'KILL'
unless (controller_events /= [])
loop
