Killing Perlbal by opening lots of slow POST requests

Brad Fitzpatrick brad at
Tue Jan 1 18:08:13 UTC 2008

I'm glad it survived your slow POST attack, as that was a specific design
goal.  I'm not so glad about the OOM.  In any case.  Which kernel and
version of Perl?  Using XS HTTPHeaders or not?

On Tue, 1 Jan 2008, Phillip Pearson wrote:

> 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.
> Cheers,
> Phil

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