Re: pen and high loads

From: Ulric Eriksson (
Date: Fri Jun 28 2002 - 01:03:33 CEST

On Mon, 24 Jun 2002, Joćo Paulo Vasconcellos wrote:

> I run a web site with an average load, that in special dates get a boost in
> traffic. We have 3 web servers load balanced by pen, and in Valentine's Day,
> my site got very slow. I tried to access each web server directly, instead of
> going thru the load balance and I got the pages very fast ( about 20 sec. ),
> while the same pages thru the load balance got 1 ~ 2 minutes to download. I
> was having 300 ~ 400 simultaneous connections, according to pen, while the
> limit I set was of 2048 clients. Anybody knows if pen does not handle well
> more than 200 connections at a time, or if it is something concerning the OS ?

The OS can be an issue. Make sure that you have enough file descriptors.
And Linux does not handle more than 1024 file descriptors in select().
That means that 2048 simultaneous connections is just not possible.

Is it possible that you have a network bottleneck? All the web traffic
(requests and replies) are going through the Pen server, so it has to
handle the total bandwidth for the whole site (twice!).

I suggest running top.

I also suggest running Pen with the control interface so you can adjust
debugging on the fly.


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