Re: [Haskell-cafe] Network Connect Timeouts

Hi Mark,

From reading the source code for *runTCPClient* [1], it looks like a thin wrapper around *getSocketFamilyTCP* and *close*.

It should be sufficient to copy that definition into your project and wrap the *getSocketFamilyTCP* call in a *timeout*. You might need to import *Data.Streaming.Network.Internal* to get access to the *AppData* constructor. Hope this helps! [1] https://hackage.haskell.org/package/streaming-commons-0.1.18/docs/src/Data-S... On Sun, Oct 15, 2017 at 9:08 AM, Mark Fine wrote:

Hi Chris,

In my application, I'm using *Data.Conduit.Network* from *conduit-extra* directly (*Data.Streaming.Network* from *streaming-commons* indirectly). The timeout I'm interested in managing is the connection establishment timeout - how long does the connect call wait to establish a connection. I haven't been able to figure out how to control this outside of applying a non-conditional timeout to the connect call (which is a timeout on the lifetime of a connection, not a timeout on the establishment of a connection). Thanks!

Mark

On Sat, Oct 14, 2017 at 3:09 AM, Chris Wong wrote:

...

Hi Mark,

What networking library are you using?

There should be a lower level interface which allows for managing the lifetime of a connection by hand.

Chris

On Oct 14, 2017 15:17, "Mark Fine" wrote:

...

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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-- Chris Wong (https://lambda.xyz) "I had not the vaguest idea what this meant and when I could not remember the words, my tutor threw the book at my head, which did not stimulate my intellect in any way." -- Bertrand Russell