Multiple Tomcat instances vs Multiple Tomcat Service(s)

Question

I have a requirement where I have to host two (different) webapps on the same machine accessible via HTTP but on different ports. I am wondering what is the better solution, or basically what is the difference between

• Starting two separate Tomcat instances with specific catalina_home / catalina_base and of course two conf dirs with corresponding server.xml(s)
• Having one Tomcat instance and configure multiple Services in a single server.xml. There is a default Catalina Service in the server.xml and adding an another with the specific ports and appbase

Could someone describe which way to choose and why? I am interested in the main differences between the two instances vs two services?

Answer 1

The main difference between both approach is:

Many Tomcat instance

You can start or stop tomcat without affect the other instances, this approach is very helpful when you need to give maintenance to one application but you don't want to affect the availability of the other instances. Each instance will use their own resources, that could be a problem when the machine couldn't guarantee the amount of memory or processor that is need by every tomcat instance, this approach will demand more resources than the other one, in terms of tomcat knowledge this approach is very easy to implement.

One Tomcat instance And Many services x webapp

This approach is helpful when you need to share the resources between the web applications, you can have one single point of configuration for all the web application, with this approach is more difficult to isolate problems between web apps because they coexist in the same tomcat instance, for example if you need to troubleshoot one application how do that if both of them are running in the same tomcat? how read the log files? are the log files of both application in one log file? or are properly separated? be careful here if no proper configuration is perform then it could be nightmare in production . This approach will need more effort and knowledge in the tomcat configuration in order to define a proper separation of services, it is more difficult to configure but in terms of efficiency is better.

How to decide

Well it depend on

a. the amount of the resources of the server.

b. the knowledge level of the IT team in terms of tomcat configuration

c. how critical are the web applications, for example if one application is very critical is better to keep it in a separated tomcat instance because it helps you to isolate in a simple form any problem that can occurs with that specific application.

And finally it will depends on the context where you need to implement your solution and your business needs.