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From David Jencks <david_jen...@yahoo.com>
Subject Multiple servers sharing the same repo and config store
Date Mon, 30 Jan 2006 07:23:10 GMT
Many people have talked on and off about how to set up multiple  
servers sharing the same repository and config-store, but we haven't  
arrived at an agreed on way to do it.  We have a prospective customer  
for this feature (Vincent Massol with Cargo) so I'd like to move  
beyond thinking about it in my head, discuss it, and have someone  
implement it.  I believe any implementation will be more or less  
trivial, the hard part is figuring out what to do.

I've only thought of ways to extend what we have now, rather than  
restructure anything or add big new capabilities.  If someone sees a  
better way, please speak up.

So, we have a ServerInfo gbean that knows where geronimo is located  
and can resolve absolute locations for other components.  Then we  
have things like the repository and config store gbeans that  
typically are "located" outside the var dir and things like the  
logging framework,  local attribute manager, derby, and tomcat, that  
typically keep stuff in the var directory.

All or most of these start with the first configuration loaded so  
they can't have any attributes overridden by config.xml: in fact this  
file is read by one of the gbeans that we need to "relocate".

I've thought of two related solutions.  Both of them involve giving  
ServerInfo knowledge of another path and another resolve method.

One would be something like "resolveVar" and would normally resolve  
to geronimo_home/var.  This would involve all the gbeans currently  
looking inside var having the "var" trimmed off the front of their  
paths and using the new resolveVar method.  In this case we'd have  
different servers represented as e.g.
var1
var2
var3
...


The other would give ServerInfo something like resolveServer which  
would normally resolve to geronimo_home.  The gbeans looking inside  
var would keep their current paths and just call the new resolve  
method instead of the old one.  In this case we'd have servers like
var
server1/var
server2/var
...

In either case I think starting geronimo with a command line argument  
pointing to the var directory is the only way to specify which server  
you want to run; the default would presumably be as now "var".

Several people have suggested putting an additional config-store into  
var for "private" use by a particular server.  At the moment I think   
that providing a different config-store class that uses the new  
resolve  method on server info would be the best way to do this.


I'm not attached to these ideas but this is as far as my thinking has  
gone.  Please comment.

thanks
david jencks



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