how to update java class files in Tomcat and save uptime

Question

Are there ways to update java class files in Tomcat without using Tomcat Manager and reloadable with saving uptime? Reloading application from Tomcat Manager takes about 15-30 seconds and it invoke locked up server. How to update a large application quickly on Tomcat?

Answer 1

Some possibilities

• setup a cluster, have a loadbalancer for multiple servers in the background. For update you remove one server from the cluster, upgrade, add to the cluster again. Then continue until done with all servers
• use a product like JRebel (development) or LiveRebel (production system). This enables you to hot-replace your code in the running instance for many usecases that required a plugin. This is a commercial option (well, running a cluster of multiple machines comes with some price as well)

Of course you can combine both options (and there are probably more that don't come to my mind right now)

It's all a question about your requirements of uptime, recovery times etc. While you're at it: Think of your database and other infrastructure as well as a possible cause for downtime.