Multiple instances of Tomcat - why would you do it ?

[Derek Clarkson <De...@lonelyplanet.com.au>]

Hello everyone,
	I've just started a new job where I've been asked to be the tech
lead on a project. The software originated from an external company who
designed it to run on 3 instances of tomcat. There is an instance for the
main applications for our customers, an instance for the admin section and
another for secure transactions. All running on the same PC. These instances
also communicate between each other in order to pass information from one to
the other via RMI. 

I've never worked on a mulit instance installation before and no-one here
knows why it was done this way (it's not documented). Can you guys give me
any thoughts on why a multi-instance might be setup like this ? What are the
advantages over a single tomcat instance, etc ? 

Essentially I'm trying to understand whether this was a good solution for
our use. Understanding the sorts of reasons for doing it will help me to
work out any possible future changes. 


Ciao
Derek.


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Re: Multiple instances of Tomcat - why would you do it ?

[Josh Rehman <jr...@citysearch.com>]

If the instances talk to each other via RMI, it's likely that the 
original developers intended each instance to be run on a different box. 
They may have thought this would positively affect scalability.

It may also be that they partitioned the app such that each container 
has different priveledges and responsibilities, and therefore it made 
sense to seperate them and configure them seperately.

It may also be that the original developer was testing a theory and so 
did it that way.

It may also be that the developers were being paid per CPU.

It may also be that one of the architects was driven mad by alien space 
bats, and so designed this system to prepare himself for leaving this 
planet.

The last one seems most likely to me. However, I could be wrong, so I'd 
ask the original developer.

Derek Clarkson wrote:
> Hello everyone,
> 	I've just started a new job where I've been asked to be the tech
> lead on a project. The software originated from an external company who
> designed it to run on 3 instances of tomcat. There is an instance for
> the
> main applications for our customers, an instance for the admin section
> and
> another for secure transactions. All running on the same PC. These
> instances
> also communicate between each other in order to pass information from
> one to
> the other via RMI. 
> 
> I've never worked on a mulit instance installation before and no-one
> here
> knows why it was done this way (it's not documented). Can you guys give
> me
> any thoughts on why a multi-instance might be setup like this ? What are
> the
> advantages over a single tomcat instance, etc ? 
> 
> Essentially I'm trying to understand whether this was a good solution
> for
> our use. Understanding the sorts of reasons for doing it will help me to
> work out any possible future changes. 
> 
> 
> Ciao
> Derek.
> 
> 
> ______________________________________________________________________
> This email, including attachments, is intended only for the addressee
> and may be confidential, privileged and subject to copyright.  If you
> have received this email in error, please advise the sender and delete
> it.  If you are not the intended recipient of this email, you must not
> use, copy or disclose its content to anyone.  You must not copy or 
> communicate to others content that is confidential or subject to 
> copyright, unless you have the consent of the content owner.
> 

-- 
Josh Rehman
citysearch.com
213.739.3559


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