Re: [vserver] Help debugging networking issue

From: Corey Wright <undefined_at_pobox.com>
Date: Tue 31 Jul 2007 - 05:29:40 BST
Message-Id: <20070730232940.56b6468e.undefined@pobox.com>

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
Received on Tue Jul 31 05:29:53 2007
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