Killing Perlbal by opening lots of slow POST requests

Phillip Pearson pp at
Tue Jan 1 05:31:49 UTC 2008

Hi all,

I've been doing some experimentation with proxies and load balancers 
over the last couple of days after a site I work on 
( had some performance problems due to spammers 
occuping all the server's Apache child processes by connecting then 
taking forever to send the payload for their POST requests.

I ended up using a custom proxy for it that I wrote some years back, but 
was interested whether Perlbal handled this situation, as it generally 
seems to be the load balancing swiss army knife of web 2.0, so I gave it 
a go.

The good news: it buffered the POST requests fine, and the site didn't 
have any trouble staying responsive while my test script created 
hundreds of fake connections.

The bad news: after creating about 600 connections, Perlbal said "Out of 
memory!" and exited.  It was using about 3G of virtual memory right 
before it died, so I'm assuming it ran out of address space.

I'm not sure if this is just because I'm a Perlbal newbie and don't know 
how to configure it properly, or if it's a generic Perlbal problem.  
Does anyone have a site running Perlbal that they wouldn't mind me 
running my script against, to see if I can reproduce the problem there?  
Or if you'd like to try it on your own server in private, e-mail me for 
a copy (I'd prefer not to encourage script kiddies by making it public, 
even though it is a pretty trivial bit of code).

I'm running Perlbal 1.60 from Subversion on Perl 5.8.8 on Debian, kernel 
2.6.17, under Colinux on a Vista laptop.  512M RAM, no swap.


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