January 2012 - 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

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Abstracting permissions with Yesod
by Felipe Almeida Lessa 03 Feb '12

03 Feb '12

Hello, everyone! I'm going to try creating a blog and my first post is dedicated to how I am writing my isAuthorized function: http://blog.felipe.lessa.nom.br/?p=7 I'd be thrilled if you could tell me if you like the idea! Something similar could be done on Yesod 0.10, either on yesod-core or on the scaffold. I didn't try writing some generic code yet because I'd like to gather comments here first. Cheers, =) -- Felipe.

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Upcoming WAI change: flushing
by Michael Snoyman 26 Jan '12

26 Jan '12

Hi all, I've just pushed a relatively minor change to the WAI spec to Github, which ties off the last hole in the specification I'm aware of. One annoyance in creating streaming responses is the issue of flushing. By using Builders, it's more difficult to make a truly streaming, realtime app, as the server will wait until a buffer is filled before sending any data to the client. This is actually a very easy problem to solve. blaze-builder provides a value called `flush` that forces the buffer to be sent, even if it's not full. The problem arises when we add one more piece: the gzip middleware. With gzip, we have an extra layer of buffering in place.[1] We need some way to force gzip to flush the buffer as well. I've put together patches to zlib-bindings, conduit, blaze-builder-conduit, zlib-conduit, and wai, that do the following: * zlib-bindings can now explicitly flush a buffer. * conduit exposes a new datatype: `data Flush a = Chunk a | Flush` * blaze-builder-conduit exposes a new function: builderToByteStringFlush, that keeps flush boundaries intact * zlib-conduit similarly has compressFlush/decompressFlush * The type of ResponseSource now has a stream of `Flush Builder` instead of `Builder` I've updated the affected WAI packages. This may seem like a major overhaul, but it actually has very limited scope. The plus side is that we can now easily do something like an eventsource app that has gzip compression applied. Please let me know your thoughts on this, or if people know of any other holes in WAI that should be plugged right now as well. Michael [1] Regarding previous discussions of using a ByteString instead of a Builder for the stream: this issue would affect either a Builder or ByteString approach, and is thus an orthogonal issue.

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ANN: happstack-server 6.5.1
by Jeremy Shaw 22 Jan '12

22 Jan '12

I am pleased to announce the release of happstack-server 6.5.1. Happstack is a powerful, flexible and well documented Haskell web development framework. For more information see: http://www.happstack.com/ Changes in this release include: - support for https:// (aka, SSL/TLS) https://groups.google.com/group/happs/browse_thread/thread/d92c24a7a81adfe8 - directory listings now sorted in alphabetical order - added Happstack class instances for ReaderT, WriterT, StateT, and RWST - happstack-server now compiles without producing any warnings - various code cleanup and formatting Discussion here: http://www.reddit.com/r/haskell/comments/os5kb/ann_happstackserver_651_http…

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[wai] wai-eventsource not released with wai 1.0?
by Bardur Arantsson 19 Jan '12

19 Jan '12

Hello, Was it intentional that wai-eventsource was not released simultaneously with WAI 1.0? Cheers,

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Split up authenticate and yesod-auth?
by Michael Snoyman 19 Jan '12

19 Jan '12

Hi all, When I started writing the authenticate package, I was the sole author of it, and I understood (to some degree) every protocol I added support for. If there was a bug report, feature request, or anything else, I had a fair idea of either how to solve it or if making the requested change would break something else. Fortunately, many people have contributed to the authenticate (and yesod-auth) packages, and the above paragraph is no longer true. I don't know what's going on with OAuth or Kerberos besides a most basic understanding, and I'm not in a position to maintain those myself. Additionally, some people are discussing adding more backends. While I want to make it clear that I appreciate the contributions, this situation has a few downsides: * When some kind of request or bug report comes to me, I have to route it to the right person, which just adds an extra step to the process. * Same thing when people ask me for assistance. * In theory, when upgrading, I could break code without even knowing it. (I don't think that's actually happened though). * The packages are both becoming rather large. On the flip side, it's very nice to have all the authentication modules centralized as they currently are. So the question is: how should future development continue? I see three choices: 1. Continue as-is. New modules can be added to these two packages, and I'll just route inquiries to the appropriate person. One minor change I'll insist on here is that authors specify in the module docs who the maintainer is, and I'll add them as contributors on Github. 2. No new modules will be accepted into these packages, they'll need to go into their own packages. 3. Even existing modules for which I'm not really the maintainer will be split off into their own packages. For options (2) and (3), we can update the docs for authenticate and yesod-auth to point to external packages that provide additional auth backends. Michael

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Please upgrade http-enumerator and/or http-conduit
by Michael Snoyman 17 Jan '12

17 Jan '12

Hi all, Thanks to Felipe for catching this issue[1]. Both http-enumerator and http-conduit will not properly reject invalid certificates. I've released updated versions of both packages: http-enumerator-0.7.2.4 http-conduit-1.1.2.2 All users are recommended to upgrade. Michael [1] https://github.com/snoyberg/http-conduit/pull/6

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ANNOUNCE: wai-routes-0.1
by Anupam Jain 14 Jan '12

14 Jan '12

Hi, I couldn't find any library that provides typesafe URLs for plain Wai applications so I modified the code in Yesod.Dispatch (yesod-core) and created wai-routes. This is my first time writing TH code so I stuck to "tweaking" the existing functionality. http://hackage.haskell.org/package/wai-routes Currently it allows you to define type safe URLs in a manner similar to Yesod. It also provides Middleware to easily insert dispatching into your application. A sample application that provides a JSON API (using aeson) - ============================================ -- A useful type synonym type UserId = Text -- Define the JSON instance data User = User { name::Text, uid:: UserId } deriving (Show, Read, Eq) instance ToJSON User where toJSON x = object [ "name" .= (name x), "uid" .= (uid x) ] -- Define the handlers getUserR :: UserId -> Application getUserR uid _req = return $ responseLBS statusOK headers json where user = User { name = "Anon Amos", uid = uid } json = encode user headers = [("Content-Type", "application/json")] getUsersR :: Application getUsersR _req = return $ responseLBS statusOK headers json where userids = (["anon","john","jane"]::[Text]) json = encode userids headers = [("Content-Type", "application/json")] -- Generate the routing datatype and the Route instance -- The type generated will be named "UserRoute" mkRoute "User" [parseRoutes| /users UsersR GET /user/#UserId UserR GET |] -- Now you can use dispatch function (passing it your route datatype) main :: IO () main = run 8080 $ dispatch (undefined::UserRoute) $ staticApp defaultFileServerSettings ============================================ Thanks, Anupam Jain

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wai and warp for conduit
by Kazu Yamamoto 13 Jan '12

13 Jan '12

Hello, I come back to my reverse proxy work today. But I could not find wai and warp repository (or branch) based on conduit. Where can I find them? --Kazu

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Implementing SPDY
by Robin Brandt 10 Jan '12

10 Jan '12

Hello there, I'm currently looking into implementing the SPDY [1] protocol based on Warp. I read in the archives that Daniel Sommermann wanted to start something similar for snap-server but I haven't seen any updates for some time. So if you've got a finished implementation somewhere in your drawer this would be a great time to publish it ;) Otherwise I'd start with the parser for the framing layer. SPDY compresses some parts of the frames using zlib. Michael already merged a small patch I wrote into zlib-bindings to support initial dictionaries so I think I'm ready to go there. Another thing that is needed to fully support SPDY is TLS. I think I'd use the tls library by Vincent here. There is some implementation work needed in the library for an extension called NPN (next protocol negotiation) which SPDY uses. Vincent offered to help here. Thanks :) (By the way, although it's possible to force at least Chrome to use non-encrypted connections "it'll break all sorts of things" according to the SPDY book [2]). With this post I'd like to start a discussion about the implementation and interfaces of this so the result can be reused in other contexts (e.g. for Snap). If you've got any suggestions and sources of inspiration I'm happy to hear them. Best regards, Robin [1] http://dev.chromium.org/spdy [2] http://spdybook.com/

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