[Haskell-cafe] Network.CGI.Compat.pwrapper

Bjorn Bringert bringert at cs.chalmers.se
Tue Feb 13 03:55:38 EST 2007

On Feb 12, 2007, at 23:27 , Albert Y. C. Lai wrote:

> Bjorn Bringert wrote:
>> pwrapper is not an HTTP server, though the Haddock comment can  
>> make you think so. pwrapper allows you to talk *CGI* over a TCP  
>> port, but I have no idea why anyone would like to do that.
> Here is a scenerio. I want a basic web application: someone makes a  
> request, and my program computes a response.
> * For one reason or another, I settle with CGI.
> * The program is huge and slow to load. (Let's say it statically  
> links in the whole GHC API and therefore is basically GHC  
> itself. :) ) It would suck to re-load this program at every request.
> * Or, the program performs work that requires more file-system  
> privilege than the admin of the web server grants. You know, a good  
> admin sets up a web server and all CGI scripts to run with nobody's  
> privilege.
> * Or, nevermind performance or privilege. I am a cheapo, and I use  
> a cheapo hosting provider, which only provides me with 3MB of  
> storage. My program weighs 17MB (recall that it links in the whole  
> GHC :) ).
> Here is a solution. The program runs as a daemon and never quits;  
> it can run somewhere with sufficient privilege and storage. It  
> talks CGI over TCP. At the web server, which is super-slow, super- 
> paranoid, and super-cheapo, the CGI script is a lightweight C  
> program that redirects everything over TCP to my daemon.
> (Here is a counter-solution. The program still runs as a daemon  
> somewhere, but it talks my own protocol over TCP. The CGI script is  
> a lightweight C program that parses CGI into my own protocol.  
> Besides having to design my own protocol carefully, here is a  
> problem: C is a great language for writing parsers that are  
> incomplete, inconsistent, and insecure. :) )

OK, that sounds reasonable, but I think that there are better  
solutions for those problems. Besides, it's niche stuff that I don't  
think belongs in the main CGI package. If anything wants it, it's  
easy to implement.

* If you have slow start-up, you can use FastCGI instead of CGI.  
There is already  a Haskell library for that.

* If the program needs additional privileges, you can use an external  
FastCGI program which is started independently of the server.

* If you have cheapo hosting, at least Apache mod_fastcgi allows you  
to run your FastCGI app on a different machine. Another solution  
would be mod_rewrite + mod_proxy. But if you have another server  
where you can run your application, why not put your web server there  
instead of using cheapo hosting?


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