I think this does what you're looking for. Note how we have to handle
the exception (via finally) that's thrown by the closing connection:
{-# LANGUAGE OverloadedStrings #-}
import Network.Wai (Application, Response (ResponseEnumerator))
import Network.Wai.Handler.Warp (run)
import Network.HTTP.Types (status200)
import Data.Enumerator (run_, ($$), enumList)
import Blaze.ByteString.Builder.Char.Utf8 (fromShow)
import Control.Exception (finally)
main :: IO ()
main = run 3000 app
app :: Application
app _ = return $ ResponseEnumerator $ \f ->
run_ (enum $$ f status200 [("content-type", "text/plain")])
`finally` cleanup
where
enum = enumList 8 $ map fromShow [1 :: Int ..]
cleanup = putStrLn "Connection closed"
On Thu, Sep 1, 2011 at 6:38 AM, Hiromi ISHII
Thanks Michael and Gregory.
On 2011/08/29, at 19:07, Michael Snoyman wrote:
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.
I understand that I have to use ResponseEnumerator to build a response to achieve my goal, right? If so, how to handle disconnections in ResponseEnumerator?
Also, for WAI, you should *not* set the transfer-encoding, that is something the backend handles for you automatically. Thanks. I fiexed it.
On 2011/08/29, at 22:10, Gregory Collins wrote:
Correct, with either WAI or Snap you will need to write an enumerator to do this.
You mean I have to use addToOutput function instead of writeLBS? I rewrote my code using addOutput as below:
= Snap Code = stream :: Application () stream = do req <- withRequest $ return . (rqRemoteAddr &&& rqRemotePort) addToOutput $ myEnumerator logError "this would never be happened..."
myEnumerator (Continue k) = k (Chunks $ map fromLazyByteString $ map (LBS.pack . show) [1..]) myEnumerator s@(Error err) = liftIO (print err) >> returnI s myEnumerator step@(Yield _ _) = liftIO (putStrLn "yielded.") >> returnI step = end =
Running snap server using this code, I accessed the page from browser and disconnect, but nothing is written in the log. What's my mistakes?
In addition, I tried to use 'settingsOnException' to handle the Exception in WAI. It could handle disconnection, but I couldn't know which conneciton is closed. Is there any method to know which connection is closed?
-- Hiromi ISHII konn.jinro@gmail.com