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From Gabriele Bulfon <>
Subject Re: Updating webapps classes
Date Mon, 03 May 2010 07:11:29 GMT
Hi, thanx for the interesting solution.
Anyway, not always possible to run 2 tomcat instances because of memory requirements.
Do you see any different solution with 1 tomcat only (or tomcat + apache)?
Thx in advance,
Gabriele Bulfon - Sonicle S.r.l.
Tel +39 028246016 Int. 30 - Fax +39 028243880
Via Felice Cavallotti 16 - 20089, Rozzano - Milano - ITALY
Da: Peter Crowther
A: Tomcat Users List
Data: 30 aprile 2010 16.33.39 CEST
Oggetto: Re: Updating webapps classes
It's very hard to do this using one Tomcat instance.  It's very easy to do
this using two Tomcat instances (call them Tomcat1 and Tomcat2) and a load
balancer (Apache httpd should be fine for this job).
In normal use, Tomcat1 is running.  The load balancer directs all users to
Tomcat1.  Tomcat2 could even be stopped.
To upgrade, you upgrade Tomcat2 (and start it if needed) and tell the load
balancer that new sessions should be sent to Tomcat2.
Once all user sessions are off Tomcat1, you upgrade it and tell the load
balancer to direct new sessions to Tomcat1.
Once all user sessions are off Tomcat2, you can shut it down again or leave
it running for fault tolerance.
If you have enough RAM on your server (and the load is low enough), you
could even run all three of Tomcat1, Tomcat2 and httpd on the same server.
Does this help?
- Peter
On 30 April 2010 14:46, Gabriele Bulfon
I don't know if I'm asking something stupid, but I'm investigating this for
days, and found
nothing around.
Updating a java webapp can be a problem when this java webapp is being ised
24/7 by users,
and many of them have sessions running for all the working hours.
Consider that this webapp consists of many instance classes being created
during session startup.
How can I manage updates of the webapp classes without having to reload the
What I would like is that users inside the application to continue to see
the old version,
while new ones logging in would see the latest one.
I don't know if there is any way for this....
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