Control the routing of load balancer from a Tomcat

Question

I have a load balancer problem. All load balancer configuration examples I have read inspect the client data and bases all load balancing routing decitions on this. I have a different problem. I need to let the application server tell the load balancer that he serves a specific url right now.

Background:

I have around 10000 hardware devices which connects to tomcat servers (by a binary TCP protocol). The tomcat servers are also serving http towards clients who would like to communicate with these devices.

I don't know when the hardware device connects (and I can't identify them on the connection) but I want all http requests from clients, which are directed towards that device to go to that tomcat-server after a device has connected. The hardware devices are load balanced by round robin dns.

Question:

Are there any good http load balancers to which I can let the tomcat server say "hey, device with id xxx just connected, please redirect all traffic towards this device to me"? The http requests are easy to identify. They have the id of the device in the request url.

Any suggestions on load balancers or google queries to make would be appreciated.

Answer 1

Interesting problem you've got there. I've had the same problem as you, but I was using jboss AS 7 instead of tomcat. However, the principles are more or less the same.

We solved this issue by using apache with mod_cluster which allows the tomcat or jboss server to register which context that it has available to the load balancer. The loadbalancer will determine which application server that has the context and route the traffic to it.

There are lots of tutorials for how to do this online, here is one good example.

http://www.devx.com/Java/Article/48086

Answer 2

For the original question, I think you are not looking for a load balancer, but just a plain reverse proxy with the twist that it has to be dynamic. Check out Apache httpd mod_proxy with mod_rewrite. For the dynamic part maybe your tomcats can register their connected "refrigerators" in a sqldb, in that case use RewriteMap with dbd.