[ic] Re: ALERT: bad pipe signal received for /page.html

Ron Phipps ron at endpoint.com
Mon Dec 11 23:32:43 EST 2006

Kevin Walsh wrote:
> Josh Lavin <josh at myprivacy.ca> wrote:
>> Is plain CGI really as fast as mod_perl or mod_interchange? That'd be  
>> my only concern with switching back to CGI+rewrites.
>> Maybe it is ok -- see mod_interchange's README:
>> "The Interchange link protocol has been
>> implemented via an Apache module which
>> saves us the (small) overhead
>> of the execution of a CGI program."
> The overhead referred to is the time taken to fork and exec the CGI
> executable.  The executable file itself will most likely be cached,
> on even lightly loaded systems, so there's no great concern over the
> time it takes to open and read the CGI program prior to execution.
> I've never been a great fan of rewrite rules, and there's a small
> overhead to be saved there too.
> Apart from any perceived efficiency enhancements, and pretty URIs
> without rewrites, mod_interchange provides a couple of facilities
> such as connection retries, failover to a backup Interchange server
> and a request drop list etc., that are not available to CGI link
> programs.
> Mod_interchange is only available for use with Apache 1.3, but that's
> not a massive problem.  Gentoo, for example, will install and maintain
> Apache 1.3 instead of 2.x if you ask it to.
> There's never been any demand for mod_interchange on Apache 2.x, which
> is the main reason why it's still only available on 1.3.  I maintain
> mod_interchange because I find it useful.  If I need to use Apache 2.x
> for some reason then I'll port it regardless of the demand, or lack
> thereof.
> I assumed that the lack of demand for mod_interchange on Apache 2.x
> was down to the availability of the Interchange::Link mod_perl module.
> Interchange::Link shares the same advantages as mod_interchange but
> seems to have its quirks.  I'm sure those will be ironed out in time,
> as long as the problems are reported.
> Any overhead saved by using mod_interchange can very quickly be eaten
> up with sloppy page code, so it's much more important to get your pages
> to be as efficient as possible, rather than worry about the relative
> merits of the various link facilities.
> www.interchange.rtfm.info uses mod_interchange, by the way.

With all the being said, I used mod_interchange with Apache 1.3.x for years on FrozenCPU and it worked beautifully during that time and if I were to setup an IC site on Apache 1.3.x today I probably would still use mod_interchange due to the reasons Kevin mentioned.

One thing that was especially nice with mod_interchange is that I could easily add files to  DropRequestList, this helped when we were attacked by a worm that was trying to exploit a XMLRPC bug which had the side effect of hanging IC due to a parsing bug.  I wasn't sure how to fix the parsing bug, but added the filename to the drop list and IC no longer hung.

Ron Phipps
End Point Corporation
ron at endpoint.com

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