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From Christoph Nenning <>
Subject Re: Tomcat clustering for simplified config
Date Wed, 07 Oct 2015 08:36:01 GMT
> Hi list,
> I just signed up to the list - please forgive any newb mistakes but 
> hopefully I'm following the right format, style and content.
> I currently work in a production environment with eight app servers,
> all running the same version of Tomcat (currently 7.0.62).  Four 
> servers support version 1 of our app, the other four servers support
> version 2.  Within each group of four, two serve completely open 
> content via 80, the other two support queries of sensitive data via 
> 443.  Servers are named with a number system where all odd-named 
> servers are for the secure content, all evens are open. 
> So here's the setup in a hopefully clearer portrayal:
> App Version 1:
> Server 01: secure queries via 443
> Server 02: open content via 80
> Server 03: secure queries via 443
> Server 04: open content via 80
> App Version 2:
> Server 05: secure queries via 443
> Server 06: open content via 80
> Server 07: secure queries via 443
> Server 08: open content via 80
> Each pair of even and odd named servers are *conceptually* linked, 
> but physically stand on their own.  All http traffic and https 
> traffic for each version is directed to a particular server by a 
> load balancer.  No Apache Web Server is in the mix and we would like
> to keep it that way for simplicity.  Load-wise, our eight Tomcats 
> are not taxed.
> I'm responsible for upkeep of these servers, which requires regular 
> version upgrades and configuration changes when any vulnerability is
> found by regular, periodic Nessus scans (
> products/nessus-vulnerability-scanner).  Sometimes the changes are 
> related to ciphers, sometimes other things, but I'd say 90% of the 
> time, I just need to upgrade to a newer version.
> So no big deal conceptually, I fully admit, but doing this across 
> eight servers is TEDIOUS.  And more importantly, it's a ripe 
> opportunity for introducing user error.  On three occasions I have 
> brought our production systems by stupid mistakes in server.xml or 
> other config files, or most recently, accidentally copying the wrong
> ROOT from a version 2 (05) box into the version one boxes (01 and 
> 03). I got things up and running fine with no serious consequences 
> but this being the third time, I thought "there has to be a better 
> way" right after I talked myself off the "you're a complete idiot" 
> I'm starting to research Tomcat clustering but everything I see just
> talks about load balancing and failover.  **What about ease of 
> configuration??** I'd like to be able to set up Tomcat <something> 
> (clusters?) to help automate what I've described above to make it 
> less tedious and reduce the chances of making stupid mistakes when 
> I'm on the 6th, 7th, 8th server.  I'm not sure if Tomcat clustering 
> is what I need, or if I should look at something else.
> Can you nice folks help direct me to where I should look for 
> starters?  Will Tomcat clustering get me what I want?  or something 
> else, like Zookeeper?
> Thanks,
> Mark Bramer

We do somthing similar by utilizing docker containers.

At first we create a base-image consisting of:
- minified linux distro
- jvm
- tomcat

Then we have application images based on that which add:
- app specific tomcat config
- the app itself

These images can be run as multiple instances and thus becoming 

When we update tomcat it is done in the base-image and all app-images are 
rebuilt and containers restarted. So it is just one place where the change 
has to be done.

On config updates the according app-image is changed, rebuilt and 


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