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From Costin Manolache <>
Subject Re: [5.0.2] New tag at the end of the week ?
Date Tue, 22 Apr 2003 19:35:14 GMT
Amy Roh wrote:

>>>Amy Roh wrote:
>>>>Hi Remy, Is the NPE in Mapper fixed with your commit?  I can't reproduce
>>>>it. Thanks,Amy
>>>Yes, it is fixed.
>> I get some NPEs in embeded.
> Can you tell me where?
>> I noticed the Engine now has a name.
>> I was thinking that each Engine will have its own domain - i.e. the
>> name of the engine will be the same with the domain. We can add a name
>> attribute, but we still need to keep each engine in its own domain.
> Why is there a need to keep each engine in its own domain *only*?
> Currently, you can keep each engine in its own domain by setting its
> domain with engine's name and also have multiple engines under one
> domain if you set it to share one domain.  It's upto how you use
> setDomain().  The default way (if you don't set domain explicitly) is to
> use engine's name for its domain.

Because having one engine per domain simplifies a lot in the naming.

Why would you want to have multiple engines per domain ? I don't see any
use case. 

You can run multiple engines in a single VM - just use a different domain.

>> Amy - do you mind if I change that ? Are you using it ?
> Yes.  I need to have a way to have multiple engines per one domain.  The
> reason for adding "name" attribute was to do so.  You can still achieve
> the previous behavior by not setting domain so I don't see why you need
> to change?  Please let me know what you think.

What I don't understand is why multiple engines per _domain_. 

I understand the use case of multiple Engines in a single VM. But why do
they need to have the same JMX domain name ? 

If you have a use case for that - what we have to do is add the extra
attribute to _all_ components in tomcat. This is the only way they can find
each other. 

In embed case, when a component is registered it needs to find the Engine 
and the other components. For that it needs to construct the name.

To recap - the  problems I have with adding another component to all names:
- it makes all code more complicated
- it needs to be done in _all_ components so they can find each other
- it doesn't provide any benefit - you can still use different domains
without problem.

If you have a use case where this would actually help - we should discuss it 
and do the change ASAP ( but on all components- I really don't see any way
embed can work otherwise ).


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