What are recommended ulimits for JBoss or Tomcat?

Resolution

• The ulimits primarily of concern are process and file limits. The limits you need depends ultimately upon your load and config.
• The main source of processes within Tomcat are typically the web connector processing threads. You'd want to ensure your process limit is at least greater than your configured max thread pool sizes. If you run multiple instances under a single user, then you'd need to account for threadpools * #ofInstances in your process ulimit.
• The file limit again would heavily depend on thread/connection limits. Each socket is a file as well and each web thread would have a socket so file limits would again need to be at least greater than your thread pool. You'd also need to consider any other common socket/file sources. For instance, does your application utilize a lot of external connections to a database or any other external resources? Does the application do any heavy file access? Be sure to account for any such activity in the file limit as well.