November 2010 - web-devel

Re: Amazon EC2 and haskell *Was: [web-devel] MochaHost for yesod applications?
by Max Cantor 15 Nov '10

15 Nov '10

Command line. I'll dig out the command later and send it to you. I found it digging around the ubuntu fora. Max On Nov 15, 2010, at 5:32 PM, Thomas Hartman wrote: > Great tip! > > How do you enable virtual memory? Linux command line thing or ec2 command thing or...? > > Cheers, thomas. > > On Mon, Nov 15, 2010 at 2:12 PM, Max Cantor <mxcantor(a)gmail.com> wrote: > The one thing you have to do on the micro instance is enable virtual memory, otherwise ld will crash (killed by signal 9 - very helpful) since GHC makes ld consume massive amounts of ram. > > Other than that, I haven't had a problem. > > Max > > On Nov 15, 2010, at 11:25 AM, Michael Snoyman wrote: > > > I've been planning on trying out their free micro instance. Does it > > provide enough power for you to actually compile things? And is email > > set up for you out-of-the-box? > > > > Michael > > > > On Mon, Nov 15, 2010 at 6:18 PM, Max Cantor <mxcantor(a)gmail.com> wrote: > >> I've started up with amazon EC2. They give you a free micro instance to get a feel for it. No arch, you're stuck with ubuntu, which seems to be alright. I have a small yesod based system running there. > >> > >> Pros: > >> - easy to massively scale up > >> - big trusted name > >> - data centers in the US (both coasts), APAC (singapore) and Europe. > >> - If a bunch of haskellers start using it, perhaps there will be better community AMIs (amazon machine image) for haskell to save us all a lot of setup. > >> > >> Cons: > >> - complete roll your own solution > >> - big trusted name (not the most personal service) > >> > >> > >> On Nov 14, 2010, at 3:43 PM, Nubis wrote: > >> > >>> I've decided to look for a cheap VPS where I can compile and run yesod applications using the latest and greatest haskell platform. > >>> I couldn't find any sane CGI/FastCGI shared host options. I'm even inclined towards developing some sort of heroku.com clone for apps running on WAI so we can solve the deployment issue for most people once and for all. > >>> > >>> I don't want to go with some obscure hosting I've never heard about and it has to be cheap (Argentinian budget). I've found mochahost has a pretty cheap VPS service with some cool OS choices. > >>> > >>> http://mochahost.com/vps.php > >>> > >>> Just thought the information may be useful for someone in the same situation as me, but I would like to hear if anyone has tried mochahost or even found an even more convenient choice for VPS. > >>> > >>> cheers! > >>> ----nubis :) > >>> _______________________________________________ > >>> web-devel mailing list > >>> web-devel(a)haskell.org > >>> http://www.haskell.org/mailman/listinfo/web-devel > >> > >> _______________________________________________ > >> web-devel mailing list > >> web-devel(a)haskell.org > >> http://www.haskell.org/mailman/listinfo/web-devel > >> > > _______________________________________________ > web-devel mailing list > web-devel(a)haskell.org > http://www.haskell.org/mailman/listinfo/web-devel > > > > -- > Thomas Hartman > Chief Technical Officer > MarketPsy Capital, LLC > 2400 Broadway, Suite 220 > Santa Monica, CA, USA > ______________________ > This e-mail message and any attachments may contain information that is confidential, proprietary or privileged, and is for the named person’s use only. No confidentiality or privilege is waived or lost by any mistransmission. If you are not the intended recipient or agent responsible for delivering it to the intended recipient, you are hereby notified that any dissemination, distribution, copying or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify us immediately and destroy all copies of this message and attachments without disclosing the contents to anyone. Neither this message nor any information included herein constitute an offer to sell or the solicitation of an offer to buy any securities or investment product, or legal, tax, accounting, or investment advice. > > The fees and expenses charged in connection with the MarketPsy Long Short Fund LP ("the Investment") may be higher than the fees and expenses of other investment alternatives and may offset profits. No assurance can be given that the investment objective will be achieved or that an investor will receive a return of all of her/his investment. Investment results may vary substantially over any given time period. An investment in this Fund is speculative and involves a high degree of risk. The performance data represents the performance of the Fund as calculated by the management company. The performance figures include the reinvestment of any dividends and other earnings as appropriate. Past performance is not necessarily indicative of future results and there is always the possibility of loss.

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"Please Break Yesod" campaign
by Michael Snoyman 11 Nov '10

11 Nov '10

Hey all, I'd like to kick off the "Please Break Yesod" campaign[1] by drawing everyone's attention to Matt Brown's commit which converts the Route associated type from a type family to a data family. tl;dr: it avoids "not injective" compiler errors, and is overall good, fuzzy and made of unicorns. I'm even told that applying it may help regrow my hair. Anyway, if people would mind pulling his code and making sure it compiles, I'd appreciate it. The last time I tried to make that transition I stumbled upon a bug in GHC 6.12.1. I don't remember what the bug was, and I don't remember what the code was, so this is mostly just me acting paranoid for no good reason. Michael [1] http://docs.yesodweb.com/blog/please-break-yesod/ [2] https://github.com/softmechanics/yesod/commit/f3afdfeea2b2cac40051ce1ad795e…

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session management
by Christian Maeder 11 Nov '10

11 Nov '10

Hi, I've tried to understand session management looking at http://hackage.haskell.org/package/clientsession and http://hackage.haskell.org/packages/archive/yesod/0.6.1.1/doc/html/Yesod-Ha… I want a server to create a (unique) session-id, send it back to the client (how?) and handle requests from the client that supply this session-id somehow (how?). Thanks Christian P.S. "cabal install yesod-examples" finally failed with: Loading package ffi-1.0 ... linking ... done. Linking dist/build/form/form ... yesod/tutorial/mkToForm.hs:11:7: Could not find module `MkToForm': Use -v to see a list of the files searched for. cabal: Error: some packages failed to install: yesod-examples-0.6.0 failed during the building phase. The exception was: ExitFailure 1

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[Yesod] blog tutorials
by いとうかつとし 11 Nov '10

11 Nov '10

Hi I'd like to learn how to use Jqeury, Nic and Crud on scaffolded by 0.6.*. Are there simple sample like as blog2 screencast(but this tutorial is too old to work on 0.6.*)? ---- Katsutoshi Itoh<cutsea110(a)gmail.com>

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Yesod's Route as a data family
by Matt Brown 10 Nov '10

10 Nov '10

Hi all, I'm trying to create a yesod subsite with "private" urls. The subsite exports widgets which reference the urls, but the urls are not intended to be referenced from the master site handlers directly. In order for this to work, the sub site needs to know how to translate it's urls into master urls. I didn't like passing the subsite route as a parameter to every widget function, so I tried a class: class YesodSubRoute sub master where subRoute :: Route sub -> Route master After confronting the dreaded "type families are not injective" error (i.e. "sub" cannot be inferred from "Route sub", etc), I rewrote it as: class YesodSubRoute sub master where subRoute :: sub -> master -> Route sub -> Route master This works, but seems a bit cludgy to me. Looking closer, I realized that mkYesodGeneral never reuses types for Route instances, which means Route actually is injective (as long as instances are only being defined by mkYesodGeneral), the typechecker just doesn't know it. As an experiment, I changed Route to a data family. It went rather smoothly, and I was able to use my original definition of YesodSubRoute (instances of which could in theory be generated by mkYesodGeneral). The only trouble I've had is exporting Route instance constructors imported from another package (specifically yesod-auth in my case), which means every module referencing auth routes has to import Yesod.Helpers.Auth). Relevant commits are below. Does this seem like a sensible approach? Are there better alternatives? thanks, -matt https://github.com/softmechanics/yesod/commit/335722b6b234841492a6fba2eb46b… https://github.com/softmechanics/yesod-auth/commit/baf9b44978aad4dba9b86cfa…

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Re: anybody have toy examples of using digestive functors formlets lib?
by Jeremy Shaw 06 Nov '10

06 Nov '10

Hello, I have a attached a little demo that shows how I like to use digestive functors. The primary issue right now is that it does not work correctly if you try to put more than one formlet on a page. (due to an issue in my code). It is fixable -- I just have not had the time and need quite yet. Though, if you can skip the use of digestiveFunctorPart and use digestive-functors-hsp the 'normal' way. To run the demo you will need: - lastest happstack from darcs - lastest digestive-functors from git, https://github.com/jaspervdj/digestive-functors - lastest digestive-functors-hsp from darcs, http://src.seereason.com/digestive-functors-hsp Furthermore, you will need to edit the digestive-functors.cabal file and change, monads-fd to mtl < 2. That will change later this week when I switch happstack from mtl to monads-fd. (Or *you* could patch happstack to use monads-fd and send me a patch). If you do not make that change, then you will get an overlapping instance error regarding MonadPlus IO. If you do not want to update to the lastest happstack, you will just have to look at the attached code and reverse engineer what you want to do. Though, I recommend upgrading to happstack from darcs. It will break your code, but I think I made all the code breaking changes for the next release, so you can get it over with now :p Or, if you are using it for a new project, you can start with the good stuff and not have to upgrade it later. The happstack crash course documents the darcs version of happstack. I will eventually add a section to the happstack crash course on this technology. But until then, I hope this gets you started. Note that the rendering is ugly because there is no CSS applied. You can use 'setAttr' in the digestive-functors-hsp library to set some class attributes and then apply some CSS to pretty things up. Also, jaspervdj mentioned something in the README about better ways to theme a form than what formlets offered. I have no idea what that refers too. But maybe it is better than using setAttrs. Note that both digestive-functors and digestive-functors-hsp are very new. If you think something about them is wacky, please let us know. Don't assume that when meant for things to be stupid. - jeremy On Fri, Nov 5, 2010 at 6:32 PM, Thomas Hartman <thomashartman1(a)googlemail.com> wrote: > anybody have toy examples of using digestive functor library? > Especially with hsp, which is my usual templating system these days? > A couple of people have recommended this library to me but I don't see any > easy way to get started using it. > Toy example would be great. > Thanks a bunch! > thomas.

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Yesod gotcha (kind of, not sure, it got me good though)
by Nubis 03 Nov '10

03 Nov '10

Hi guys, I'm fully getting into haskell thanks to the yesod framework. I've been pulling my hair with a bug as silly as they come, and for so long that I cannot tell it without feeling embarrassed. (I'm working on the haskellers.com website code, just to give you some extra context) I was getting a 500 in one of my controllers, and I first though there was some non existing id being referenced from a model, I set up the haskell interactive debugger and launched my yesod project from ghci, single stepped and everything looked just fine. The actual error displayed was:"Internal Server Error" "A LineSingle must have nested content" The issue was finally that a cassius file had some trailing garbage (that went unnoticed by me, probably added accidentally when passing out over my keyboard). My main issue with this is that I think of cassius files as just css, I wouldn't expect to get an error in my page just for a broken css file. I would expect seeing broken styles, or even better, the program not compiling at all. I searched for the LineSingle error message and seems to be related to hamlet, I interpreted that as a pointer but was in the wrong direction. I know this won't happen to me again, but just wanted to throw it out here to see if you consider it a gotcha. cheers :) ----nubis :)

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Single step debugging a yesod application
by Nubis 03 Nov '10

03 Nov '10

Hi guys, As I said in another thread, I've been debugging a yesod application single stepping through one of the handlers. I'm using ghci built in debugger and it's pretty good, but I always fail to set the breakpoint in the right scope where I can evaluate the stuff I'm interested in learning more about. For instance, in the following code I would like to set the debugger on the line before "mv <- maybeAuth", in order to :force the values of (uid, u). But even when I set it at the beginnig of the 'mv' line, the scope ends up being the entire do block. Which makes sense, but doesn't helpe me solve my problem :) getUserR :: String -> Handler RepHtmlJson getUserR input = do (uid, u) <- case readIntegral input of Just uid -> debugRunDB $ do u <- get404 uid mun <- getBy $ UniqueUsernameUser uid case mun of Nothing -> return (uid, u) Just (_, Username _ un) -> lift $ redirect RedirectPermanent $ UserR un Nothing -> debugRunDB $ do mun <- getBy $ UniqueUsername input case mun of Nothing -> lift notFound Just (_, Username uid _) -> do u <- get404 uid return (uid, u) mv <- maybeAuth Maybe the problem is that I'm thinking in a too procedural fashion about do blocks, or that evaluating those results is kind of paranoid. I'm too spoiled by REPL's, I would even like to be able to use a REPL that runs inside runDB for querying models and doing stuff with them interactively. How do you debug your yesod apps? am I drifting too far away from the haskell way? thanks in advance for your comments :) cheers ----nubis

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[Yesod] How can I layout 2 random banana forms into 1 page?
by いとうかつとし 02 Nov '10

02 Nov '10

Hi, I'm beginning to learn yesod programming. I just write random banana tutrial.(ref. http://docs.yesodweb.com/book/forms/) And the program work good, after installed safe package. Now, I'd like to layout 2 paramsFormlet into 1 page(getHomeR) and expect to work independently. But my program(with this mail) don't work independently. I know these id and name attributes of input tags are same between 2 paramsFormlet's. But I don't know why and how to modify. Could you tell me a solution? ---- Katsutoshi Itoh <cutsea110(a)gmail.com>

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New Persistent Meta-Backend for Horizontal Partitioning - Difficulty?
by Max Cantor 02 Nov '10

02 Nov '10

I like Persistent for its simplicity and ease of use compared to the other, more full-featured DB libraries on Hackage. There is one feature which I am interested in but am curious what the community thinks of it. My idea is to support horizontal partitioning via a new Persistent backend which is more of a meta backend that redirects queries to any number of child backends. I think it shouldn't be too difficult. Persistent's simplicity and not supporting joins makes this much easier. The meta-backend simply needs have references to the child back ends and some sort of "chooser" function that says which data goes where. Queries which need to be executed across the children could run in parallel (with some restrictions on things like sorting). Anyway, just a thought. I'm curious if this community thinks this would be useful given that tools like pgpool exist. I've heard some bad things about pgpool which is why I was thinking about this. Furthermore, glancing at the code for the current backends, it doesn't *seem* like a ton of work, but I am far from convinced. So, what does everything thing?

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