September 2011 - web-devel

"Wiki" section of the Yesod doc site
by Michael Snoyman 13 May '12

13 May '12

Hi everyone, I've added a new section to the Yesod doc site: the wiki[1]. This section is intended to be user-writable, so if you have any content you'd like to submit, please go ahead. In particular, this section contains the "Powered by Yesod" page: please add your sites. Unfortunately, the list from the old wiki was lost when my previous VPS died. (All my databases were backed up, I just forgot to backup the Wiki content as well...) Michael [1] http://www.yesodweb.com/page/wiki

5 7

A WebSocket library
by Jasper Van der Jeugt 05 Oct '11

05 Oct '11

Hello all, I have been working on a WebSocket [1] library lately, which you can find here [2]. It's getting to the point at which I want to release it on Hackage. However, there is one thing remaining before the library will be really useful for applications: integration. I would like to provide integration with Happstack, Snap and Yesod -- this is why I have built the library around the enumerator package [3]. It would be awesome if frameworks could more or less agree on a way in which an HTTP connection can be "transformed" to a WebSocket. That way, I will be able to provide packages such as `websockets-warp`, `websockets-snap` etc. Currently, the "entry point" of the websockets library is the following function: runWebSockets :: WebSockets a -> Enumerator ByteString IO a -> Iteratee ByteString IO () -> Iteratee ByteString IO a Where the first argument is the user-supplied code in the `WebSockets` monad (needs to keep a bit of state etc.), the second argument is an enumerator which the library can use to read from the socket, and the last argument is an iteratee with which the library can write to the socket. A web server then needs to provide some way to get this enumerator/iteratee pair, and hand it over to the library (currently, this is lacking). Some more details apply, e.g. the web server shouldn't kill the websocket handler as fast as regular HTTP connections. Is this proposal somewhat agreeable? I'm open to any feedback. [1]: http://en.wikipedia.org/wiki/WebSocket [2]: http://github.com/jaspervdj/websockets [3]: http://hackage.haskell.org/package/enumerator Cheers, Jasper

7 11

Happstack plugin warnings
by Asafe Ribeiro 24 Sep '11

24 Sep '11

Hi, I'm using the happstack plugin to avoid recompiling my templates. However if I get a warning my page does not render, instead it shows the warnings on the browser. Is there any workaround ?

2 1

Yesod development server auto-build
by Ramon Snir 24 Sep '11

24 Sep '11

I'm trying out Yesod, but when the Yesod development server is running, on every file change it rebuilds the application. A great feature, but when saving several files (with Ctrl+Shift+S), it builds the application multiple times - once for every file. Is there a way to configure it so it won't do that? Thanks, Ramon Snir *---* *"What better use is there for the human body, than to serve the human mind?"* -- Freeman J. Dyson

1 0

yesod init && wai-handler-devel
by Balázs Endrész 05 Sep '11

05 Sep '11

Hi everyone, I've just tried Yesod for the first time, and managed to get the site produced by the scaffolder working with wai-handler-devel. But currently there seem to be a couple of issues with it: 1.) #ifdef WINDOWS macros doesn't work with wai-handler-devel, on Windows it tries to load System.Posix.Signals in Application.hs 2.) in wai-handler-devel.hs I had to set the `yesod` field of the `Devel` data type to True because otherwise it wouldn't work 3.) in Application.hs the withFoundation function takes two extra arguments, so it produces a scary error message if one tries `wai-handler-devel 3000 Application withFoundation`. This can be solved with something like this: withFoundation' f = do conf <- Settings.loadConfig Settings.Development -- logger <- makeLogger let logger = undefined s <- static Settings.staticDir Settings.withConnectionPool conf $ \p -> do runConnectionPool (runMigration migrateAll) p let h = Foundation conf logger s p toWaiApp h >>= f but then the logger produces some strange things: Interpreting success, new app loaded GET / Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 GET /static/css/normalize.css AccepGtE:T t/esxtta/tciscs/,t*m/p*/;-qf=n0M.a15 eGBE.Tc s[Gs(E "TAE cT/ckse7tp_atft:2i vct"/e,tx"mt"p/)/c]5s ts-,J*H/Q*-;Sq.=j0s. 1A ccept: */* GET /favicon.ico Accept: */* AAAcccccceeepppttt::: *tt/ee*xx tt//ccssss,,**//**;;qq==00..11 What could be the problem here?

2 1

Re: [web-devel] Handling disconnection in wai or warp
by Michael Snoyman 01 Sep '11

01 Sep '11

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 <konn.jinro(a)gmail.com> wrote: > 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(a)gmail.com > > > >

1 0