Subject: Re: [vserver] Help debugging networking issue
From: Corey Wright <undefined@pobox.com>
Date: Mon, 30 Jul 2007 23:29:40 -0500

On Tue, 31 Jul 2007 12:02:17 +0930
Michael Terrington <michael@terrington.id.au> wrote:

> I have an AMD64 host running multiple vservers.  One of the vservers 
> runs a HTTPS reverse proxy (pound) which maps calls through to Apache on 
> another vserver.

sounds like my setup, but with apache2 as reverse proxy: debian etch amd64
host with apache2 (ssl/gzip) forwarding to various other apache2 instances
in different vservers (each running a different web application).

> Occasionally I get an error where the Apache vserver just doesn't 
> respond to the reverse proxy for a request.  The log on the reverse 
> proxy indicates "error reading from host".

the only time i've seen something like that was with php out of memory
(memory_limit) errors that were being passed up from a backend apache2
instance to the reverse proxy and the reverse proxy didn't know how to deal
with it.

> I've tried tcpdump but I don't see any output which I presume is because 
> it's internally routed...  So how can I debug this further?

tcpdump -i lo host <pound> and host <apache> and tcp port 80

> In case this is an old issue, I'm running a pre-built Ubuntu dapper 
> kernel from http://ubuntu.uni-klu.ac.at/ ... 
> linux-image-2.6.15-27-amd64-k8_2.6.15-27.45vs2.0.1+2.0.2rc26_amd64.deb

for the record i'm running 2.6.21 from debian testing (2.6.18 in etch
reports hiccups in my sata drives and degrades my software raid arrays and
i haven't upgraded to the recent 2.6.22 in unstable yet).

corey
-- 
undefined@pobox.com