Re: [web-devel] Handling disconnection in wai or warp

Correct, with either WAI or Snap you will need to write an enumerator to do this. I don't know much about WAI, but with Snap you may also need to call "getTimeoutAction :: MonadSnap m => m (Int -> IO ())" in order to get a closure that you can use within your enumerator to prevent the long-running connection from timing out (the default is something like 20s IIRC). In Snap (and likely also in WAI), if the client connection is disconnected, unless you have some side-effecting cleanup to do, you shouldn't need to do anything special. If you do need to run some side-effecting cleanup code, you should be able to catch the exception thrown by the socket iteratee using the MonadCatchIO instance provided in Snap. G On Mon, Aug 29, 2011 at 12:07 PM, Michael Snoyman wrote:

On Mon, Aug 29, 2011 at 1:03 PM, Hiromi ISHII wrote:

...

Hi there,

I am writing a simple server which returns infinite stream of data to client like Twitter's streaming API.

I have to manage the number of clients and the connection times of each one. So I have to handle disconnections during server sending a response to the client.

I'm currently considering using wai (+warp) or snap framework. My code fragments for snap and wai are below:

==== snap ver. application ==== stream :: Application () stream = do  req <- withRequest $ return . (rqRemoteAddr &&& rqRemotePort)  writeLBS $ LBS.unlines $ map (LBS.pack . show) [1..] -- I have to handle disconnection here ==== end ====

==== wai ver. ==== streamHandler :: Application streamHandler req = do  return $ responseLBS statusOK                       [ ("Content-Type", "application/json")                       , ("Transfer-Encoding", "chunked")                       ]                       (LBS.unlines $ map (LBS.pack . show) [1..]) -- I have to handle disconnection here ==== end ====

Thanks,

-- Hiromi ISHII _______________________________________________ web-devel mailing list web-devel@haskell.org http://www.haskell.org/mailman/listinfo/web-devel

I'm not entirely certain what's going on here, but my guess is that for either WAI or Snap you'd want to use the enumerator interface instead of lazy ByteStrings. Also, for WAI, you should *not* set the transfer-encoding, that is something the backend handles for you automatically.

Michael

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