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From Amy Roh <amy...@sun.com>
Subject Re: [5.0.2] New tag at the end of the week ?
Date Tue, 22 Apr 2003 20:02:30 GMT


Costin Manolache wrote:
> 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.

I agree this simplifies things.

> 
> 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 ).

Here is my use case and background info.  I need to create multiple 
engines (one engine per connector) because in TC we support defaultHost 
in engine level.  However, AppServer that I'm working on supports one 
defaultHost per listener(connector).  This forces me to create one 
engine per listener which results in having as many engines as listeners 
to map AppServer domain.xml and TC server.xml.  AppServer has its JSR77 
mbeans for domain, server, applications, ejbmodules, etc.  We want to 
use Tomcat MBeans for WebModules & Servlets sharing one default domain. 
  Not allowing multiple engines per domain means that the deployed 
WebModules will have different domains which doesn't follow JSR77. 
Maybe you have a better idea/suggestion to resolve this issue if we 
don't allow multiple engines per domain.

Thanks,
Amy


> 
> 
> Costin
> 
> 
> 
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