I'd like a configurable network connect timeout. Has anyone solved this reasonably?

System.Timeout.timeout times out connections, but works on the granularity of the life of the connection. Is there a reasonable way to configure a timeout around just establishing the connection? Maybe something like a conditional timeout that enables an action to disable the timeout once it expires?

As a workaround, I'm spinning trying to successfully connect first before trying to connect for real:

-- | Try the TCP connection and see if you can connect...

--

tryTCPClient :: Int -> ClientSettings -> IO ()

tryTCPClient microseconds settings = do

  ok <- newIORef False

  void $ timeout microseconds $ runTCPClient settings $ const $

    writeIORef ok True

  ok' <- readIORef ok

  unless ok' $

    tryTCPClient microseconds settings

-- | Wrap runTCPClient with a connect timeout.

--

-- Tries the TCP connection first, and the runs the regular runTCPClient.

-- Of course, this only enforces a TCP connect timeout on the first connect.

-- The second TCP connect has no timeout :(

--

runTCPClient' :: Int -> ClientSettings -> (AppData -> IO a) -> IO a

runTCPClient' microseconds settings action = do

  tryTCPClient microseconds settings

  runTCPClient settings action

I've also tried running the tryTCPClient in its own thread concurrently with runTCPClient and throwing an exception if it can't connect in microseconds. None of these offer an actual true connection establishment timeout.

Has anyone found a way to solve this? Thanks!

Mark

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