AJP13 made easy with mod_proxy

March 18th, 2008 Radim Marek Posted in Administration, jboss |

For a long time mod_jk has been preferred Apache HTTPD plug-in that allowed integration with Tomcat’s JK connectors. It’s certainly perfect solution and still the recommended one for mission critical and highly loaded scenarios.

In case your setup is more relaxed and you looking to do first setup with AJP, there is another solution – mod_proxy. More precisely mod_proxy_ajp that provides ability of handling AJP 1.3 protocol. These modules are enjoying comeback since they have been rewritten for Apache HTTPD 2.2.

Main benefit behind using mod_proxy is the fact that most of the Apache HTTPD installations already come with this module precompiled. Very often not only with HTTP support, but AJP as well. In such a situation administrators feel more tempted to experiment with HTTP based load-balancing scenarios, and therefore more likely to experiment with different protocol.

Let’s have a look how sample configuration would look like:

# Enable Reverse Proxy
ProxyRequests Off

<Proxy balancer://mycluster>
        Order deny,allow
        Allow from all

        # loadfactor = worker load factor
        # route = jvmRoute appended to SESSIONID, reflecting setting in server.xml
        # min = minimum number of connections to backend server
        # max = maximum number of connections to backend server
        BalancerMember ajp://192.168.10.33:8009/ loadfactor=10 route=33 min=10 max=50 keepalive=On
        BalancerMember ajp://192.168.10.34:8009/ loadfactor=2 route=34 min=10 max=50 keepalive=On
</Proxy>

ProxyPass /proxy balancer://mycluster STICKYSESSION=JSESSIONID|jsessionid nofailover=On
ProxyPassReverse /proxy balancer://mycluster
ProxyPassReverseCookieDomain backend.server public.server

In this case two nodes are created to participate in load-balancer using AJP as connector to backend Tomcat; session affinity enabled with STICKSESSION configuration.

Overall the configuration corresponds with the one you would normally create using mod_jk. Now you’re probably asking what’s the catch. And answer is simple – you loosing dynamic options (periodic reload of mapping), only simplified balancing features and generally the performance is slightly behind mod_jk. My tests during last few months (both with experimental and production grade setups) show difference approximately about 6 – 7% drop down. Something not really worrying if you’re running medium sized intranet solution and you already need clustered solution, or if you just discovering world of load balancing.

For more information, please, check following resources:

• Mod_proxy documentation
• Mod_proxy_ajp documentation
• Apache Tomcat Connector