Thx for taking the time to read the post.
You're right in that it's difficult to determine whether Apache is the problem, however, there's nothing sitting between the proxy and the app server and the only things that are running on the app server are apache (mod_perl) and sendmail.
Having reviewed the access and error log on the proxy I can see an entry for a request that subsequently fails, however, neither the access or error logs on the app server have an entry for the request. This suggests that the request is never reaching the app server but as there's only one hop between them I'm struggling to understand what is happening to the request from the proxy.
Rgds,
Cris
-----Original Message-----
From: Boyle Owen [mailto:Owen.Boyle@xxxxxxxxxxxxx]
Sent: 27 November 2009 09:17
To: users@xxxxxxxxxxxxxxxx
Subject: RE: mod_proxy issue - intermittent 502 response
502 is bad gateway, which means that apache and the back-end server have
got into a protocol argument. Usually this is due to a bad response from
the back-end (as your log entries indicate). Why do you think apache is
the problem?
Rgds,
Owen Boyle
Disclaimer: Any disclaimer attached to this message may be ignored.
________________________________
From: Cristian Pini [mailto:cris.pini@xxxxxxxxx]
Sent: Thursday, November 26, 2009 6:19 PM
To: users@xxxxxxxxxxxxxxxx
Subject: mod_proxy issue - intermittent 502
response
Hi,
I'm running Apache/2.0.52 as a reverse proxy on a RHE4 box, the
backend app server is on a separate machine again RHE4, running
Apache/2.0.52 and mod_perl 1.99_16.
There are intermittent 502 responses being generated by the
proxy although a page refresh generally resolves the issue, we are
trying to get a configuration of 2 RP boxes in front of 3 mod_perl app
servers into production but will need to understand / resolve the issue
of these intermittent 502 responses first.
[Thu Nov 26 15:35:09 2009] [error] [client 88.96.233.45] proxy:
error reading status line from remote server xxx.xxxxxx.co.uk, referer:
http://xxx.xxxx.co.uk/mens/casual/casual/71/brand-/all-/start-
[Thu Nov 26 15:35:09 2009] [error] [client 88.96.233.45] proxy:
Error reading from remote server returned by
/mens/smart/smart/70/brand-/all-/start-, referer:
http://xxxx.xxxxxxx.co.uk/mens/casual/casual/71/brand-/all-/start-
Can someone shed further light on what the problem is and how to
resolve it pls, I'm happy to send virtual host confs if someone wishes
to dig little deeper. Note at this point I'm using mod_rewrite [P] to
proxy the requests to the app server rather than using ProxyPass as we
have many rewrites in the conf.
I've googled around and have seen that others have observed
similar scenarios when using this setup in Apache 2.0 but have not seen
anything specific about a resolution or path to resolution.
Your help gratefully appreciated.
Kind regards,
Cris
Cristian Pini
Foresite Business Solutions Ltd
Tel: 020 8540 0040
Direct: 020 8545 6813
http://www.fsite.com
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