plesk: how to configure reverse proxy rules properly?

Question

[edit]: FWI, thanks to Vadym's comment below, I discovered that I had overlooked to enable mod_proxy_http on my Plesk server. Loading this module (alongside mod_proxy) fixed the original error.

I'm trying to configure reverse proxy rules in vhost.conf. I have Apache-2.2.8 on Ubuntu-8.04, monitored by Plesk-10.4.4.

What I'm trying to achieve is defining a reverse proxy rule that defers all traffic to -say- http://example.com/tomcat/ to the Tomcat server running on port 8080. I have mod_rewrite and mod_proxy loaded in Apache. As far as I understand mod_proxy docs, entering following rules in /var/www/vhosts/mydomain/conf/vhost.conf should work:

<Proxy *>
  Order deny,allow
  Allow from all
</Proxy>

ProxyRequests off
RewriteRule ^/tomcat/(.*)$ http://example.com:8080/$1 [P]

Yet, I am getting a HTTP 500: internal server error when requesting above URL. (Note: I decided to use a rewrite rule in order to at least get some information logged.)

I have made mod_rewrite log extensively, and find following entries in the logs [note: due to a limitation of max. 2 URLs in posts of new users, I have modified all following URLs so that they only contain 1 slash after http:. In case you're suspecting typos: this was done on purpose):

192.0.2.23 - - [19/Mar/2012:16:42:59 +0100] [example.com/sid#b06ab8][rid#1024af8/initial] (2) init rewrite engine with requested uri /tomcat/testApp/
192.0.2.23 - - [19/Mar/2012:16:42:59 +0100] [example.com/sid#b06ab8][rid#1024af8/initial] (3) applying pattern '^/tomcat/(.*)$' to uri '/tomcat/testApp/'
192.0.2.23 - - [19/Mar/2012:16:42:59 +0100] [example.com/sid#b06ab8][rid#1024af8/initial] (2) rewrite '/tomcat/testApp/' -> 'http:/example.com:8080/testApp/'
192.0.2.23 - - [19/Mar/2012:16:42:59 +0100] [example.com/sid#b06ab8][rid#1024af8/initial] (2) forcing proxy-throughput with http:/example.com:8080/testApp/
192.0.2.23 - - [19/Mar/2012:16:42:59 +0100] [example.com/sid#b06ab8][rid#1024af8/initial] (1) go-ahead with proxy request proxy:http:/example.com:8080/testApp/ [OK]

This suggests that the rewrite and proxy part is processed ok; still the proxied request produces a 500 error. Yet:

• Addressing the testApp directly via http://example.com:8080/testApp does work.
• The same setup does work on my local computer.

Is there something else (Plesk-related, perhaps?) I should configure?

Solution

Are there any clues within ErrorLog?

Have you tried the same thing without mod_rewrite (just mod_proxy) like this:

  <Location /tomcat>
    ProxyPass http://example.com:8080/
    ProxyPassReverse http://example.com:8080/
  </Location>

Comments

[rvdb]

Thanks for your suggestion. I had tried normal proxy rules before (and have now tried to put them inside <Location> as you suggested). Same result: HTTP 500 error, without any trace at all in error.log (nor any other logfile I can find, which is quite maddening). Actually, that's why I resorted to a RewriteRule, to get at least some logging.

[Vadym S. Khondar]

As just a random shot, do you have mod_proxy_http enabled in your server config?

[rvdb]

Spot on, nice shot! Sorry for having overlooked this trivial config issue. You already made the first day of my week, Vadym. Thanks a lot!