Tomcat - one thread per request - or other alternatives?

Question

My understanding is that in Tomcat, each request will take up one Java/(and thus OS) thread.

Imagine I have an app with lots of long-running requests (eg a poker game with multiple players,) that involves in-game chat, and AJAX long-polling etc.

Is there a way to change the tomcat configuration/architecture for my webapp so that I'm not using a thread for each request but 'intercept' the request and response so they can be processed as part of a queue?

Answer 1

I think you're right about tomcat likes to handle each request in its own thread. This could be problematic for several concurrent threads. I have the following suggestions:

• Configure maxThreads and acceptCount attributes of the Connector elements in server.xml. In this way you limit the number of threads that can get spawned to a threshold. Once that limit is reached, requests get queued. The acceptCount attribute is to set this queue size. Simplest to implement but not a good long term solution

• Configure multiple Connector elements in server.xml and make them share a threadpool by adding an Executor element in server.xml. You probably want to point tomcat to your own implementation of Executor interface.

• If you want finer grain control no how requests are serviced, consider implementing your own connector. The 'protocol' attribute of the Connector element in server.xml should point to your new connector. I have done this to add a custom SSL connector and this works great.

• Would you reduce this problem to a general requirement to make tomcat more scalable in terms of the number of requests/connections? The generic solution to that would be configuring a loadbalancer to handle multiple instances of tomcat.