Apache HTTP load balancing based on URL pattern

Question

I have a Apache web server in front of 2 tomcats which are connected to the same MySQL backend database.

I need to load balance the incoming requests between two tomcats based on a URL parameter named "projectid". For example all even project ids may be served with tomcat 1 and odd requests with tomcat 2.

This is required because the user may start jobs in a project of tomcat 1 which tomcat 2 won't be aware of and these jobs are currently not stored in the database.

Is there a way to achieve this using mod-proxy-load-balancing?

Answer 1

I'm not aware of such a load algorithm being already present. However, keep in mind that the most common loadbalancing outcome (especially when you have server-side state as you obviously have) is a sticky session: You're only balancing the initial request. After that, all requests are typically directed to the same server.

I typically recommend against distributing the session data as it adds some commonly unnecessary performance hit onto each request, negating the improved performance that you can get with clustering. This is subject to be changed in actual installations though and just a first rule of thumb.

You might be able to create your own loadbalancing algorithm with mod-proxy-load-balancing (you'll need to configure the algorithm in the config file), but I believe your time is better spent fixing your implementation, or implement business specific logic to check all cluster machines for running jobs.