RE: PerlTransHandler question

[prev] [thread] [next] [Date index for 2005/03/10]

Thanks for the detailed response; all your assumptions are correct
almost... Maybe if I give a bit more detail on the structure someone
could suggest a better strategy.

I have one apache server with mod_perl enabled. I have done a fair bit
of tuning and preloading so it runs quite well, one of its main
functions is to allow users to upload images, it then cuts the images up
into different sizes and places them in different directories. Although
recently users have been uploading large pdf catalogs which they claim
are very important..... Currently this server is the only server running
and serves up every page

<FilesMatch "\.htm$">
	SetHandler perl-script
	PerlModule Apache::ASP
	PerlHeaderparserHandler Apache::SearchBot
	ExpiresActive On
	PerlHandler Apache::ASP
	PerlSetVar UseStrict 1
	PerlSetVar Debug 2
	PerlSetVar Global /tmp	
</FilesMatch>

My main problem is then when general browsers start to download these
pdfs they hold a mod_perl connection open for way to long. There for I
have set up images.webserver.com which is just a small apache server
that is not using mod_perl and that is what is listed in my previous
message.


I am aware that I could just change the links to the pdfs but that is
allot of code changes and may cause problems with the image upload code
etc. My desired solution is to keep the mod_perl as the front end and
have something else serve up the images, I have been fooling around with
mod_rewrite but havent been able achive the desired effect. I have tried
variations of the following.

<FilesMatch "\.htm$">
	RewriteEngine On
	RewriteRule \.(htm|html|cgi|images)$ - [last]
	Options FollowSymLinks
	RewriteRule ^/(.*)$ http://images.webserver.com:80/$1 [r]

	SetHandler perl-script
	PerlModule Apache::ASP
	PerlHeaderparserHandler Apache::SearchBot
	ExpiresActive On
	PerlHandler Apache::ASP
	PerlSetVar UseStrict 1
	PerlSetVar Debug 2
	PerlSetVar Global /tmp	
</FilesMatch>


Another reason why I would like the mod_perl server to be the front end
is because it has ssl enabled and there will be problems with the cert
across different server.


Any thoughts?


Shawn



-----Original Message-----
From: Tony Clayton [mailto:tony@xxxxxxx.xx] 
Sent: Tuesday, March 08, 2005 8:15 PM
To: modperl@xxxx.xxxxxx.xxx
Subject: Re: PerlTransHandler question

Quoting shawn <shawn@xxxxx.xxx>:


> So far this working on my development environment, but what I am
really
> wondering about is if this will actually take the load off mod_perl?
> (it's a little hard for me to tell without significant traffic) Will
the
> mod_perl server execute the page and release the connection and not
care
> how long the images server is taking? If anyone has a better solution
or
> an idea I would love to hear it.

OK, this is a little confusing... it's hard to tell what you are doing
here.
First, I'm not sure I'd assume that a CPU usage spike can be blamed on
apache
serving up images.  That should be mostly disk reads and I wouldn't
expect it
to effect CPU much.  Good monitoring, logging, and load-testing might be
in
order.

Second, I'm going to assert a few assumptions on what you are doing:
1) you are running (at least) two apache/mod_perl webservers... one for 
serving
static content and one for serving mod_perl requests
2) You have installed this TransHandler on both web servers, for
whatever
reason, which is why you have the if statement
3) You are therefore NOT running images.webserver.com and webserver.com 
from the
same apache server instance, as you realize that this doesn't solve 
your problem
4) You also realize that the TransHandler doesn't make much sense
(AFAICT) if
assertion #2 is not true.

If any of these assertions are false, we may need to back up a bit.

If these assertions are all true, then I see what you are trying to do
(and in
theory it could work), but it's worth mentioning the following:
- you could send images.webserver.com in the original content, thus 
avoiding the
browser redirect and eliminating the need for the TransHandler
- I'm not sure why you would need/want mod_perl on the static content
server
- you could alternatively use mod_rewrite

Note also that if you are on an OS with copy-on-write memory pages (ie:
linux)
then you can keep the apache children thin and light by preloading your
mod_perl modules in the parent.  If children are thin and light, you can
run
more of them for the same bang/buck.  If you are really diligent at
preloading
things, then you may find that the original apache/mod_perl is light
enough.

You might want to consider running two apaches together:
1) apache/mod_ssl/mod_proxy/mod_gzip/mod_mmap_static server as a
front-end
2) proxying to the apache/mod_perl backend

See also:
   http://perl.apache.org/docs/1.0/guide/performance.html

If your primary concern is slow clients, then you might consider
mod_gzip.

And the obvious of course... keep your images as small as possible, or
provide
smaller, clickable thumbnails.