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From Stephen McConnell <mcconn...@apache.org>
Subject Re: management of merlin/fortress-hosted components
Date Mon, 05 Aug 2002 13:11:28 GMT

Leo Simons wrote:

>I have a CMS application which runs in a servlet environment, currently
>using a forked phoenix. As merlin/fortress is approaching a stage where
>it is usable as a replacement for this forked phoenix, and phoenix is
>not going the embeddable path, I am looking at replacing my fork with
>the latest merlin/fortress.


>First issue: the application needs to offer remote management through a
>web interface. Currently I have a java applet (yes, I actually wrote an
>applet, my second ever!) acting as a JMX client to the phoenix RI JMX
>adaptor (the fork is before baxter got separated out).
>I would like to keep basically the same setup, where merlin/fortress
>exports all its managed components via JMX.

In Merlin the Kernel is the principal manangement point.  The Kernel is 
becically nothing more than a manager of a root container. A kernel 
behaves synchronously towards its clients wheras the container is 
asynchornouse (i.e. firing up a kernel resulting in fireing up its root 
container which results in the parrallel firing up of the root contain's 
subsidiary containers - containers notify their logical containers of 
things like initialization and startup via events).  My immediate guess 
is that what you need it to be able to launch a Kernel and then access 
meta info/data about it and use this information to manage the instance. 
 Over the last few days I've been putting in place extra container 
fuctionality to support conterin based speciailizations - what you 
descriping would need a little extra work on the kernel to provide the 
meta info/data access and the ability to declare a specialized container 
class (both of which should be reasonably easy to put in place).

>One option is to create a MX4J wrapper component and a customized
>container with the container depending on the MX4J component, and then
>plugging that into the merlin kernel (at least I think it is).

If you can handle the MX4J dependecy as part of the container 
initialization - not problem.  Containers are part of the bootsdtrap 
infrastucture which means a formal dependency declaration by a container 
isn't going to work.  Dependecies are ok for components and extensions. 
If you really need the dependency declaration then it total possible to 
declare you container as a component with dependecies - the only 
difference is that as a component it canot dynamcially add services into 
the overall appication scope (whic is (a) probably not an issue, and (b) 
causing you to wonder what the heel I'm talking about).  To summarise - 
kernels and containers are part of the bootstrap process and are treated 
in a special way.  However kernels and container are component and can 
be embedeed as such.  Currently Merlin provides support for specialied 
containers - but specialized kernel support is pending.

>The other option is to modify merlin/fortress to use MX4J directly.

I really need to know what information you need from the kernel.

>I am a bit unsure which road y'all want to go with this. I am also
>unsure where to start. I also need to start with this *now*, instead of
>when the merlin/fortress merger is complete (code maintainance for this
>part of the application will go to someone else, and the phoenix fork is
>quite difficult for anyone besides me and perhaps PD to figure out at

I can put some time in to make this possible.  

>Can the fortress/merlin people offer some advice?
>Leo Simons
>BTW, our company is likely going to give green light for open sourcing
>this CMS app soon! :D

That's interesting - do you have any information about the app?



Stephen J. McConnell

digital products for a global economy

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