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From David Jencks <david_jen...@yahoo.com>
Subject Re: Pulling Geronimo Configuration
Date Wed, 11 Feb 2009 00:32:11 GMT

On Feb 10, 2009, at 1:52 PM, Russell E Glaue wrote:

> David Jencks wrote:
>>
>> On Feb 10, 2009, at 8:09 AM, Chance Yeoman wrote:
>>
>>>
>>> Hello All,
>>>
>>> I am interested in setting up geronimo installations that can pull
>>> installed plugins and their dependencies exclusively from a  
>>> repository
>>> within a master geronimo server.  I hope to eventually have an
>>> automated process allowing cluster members to poll a cluster- 
>>> specific
>>> geronimo server repository for available, locally uninstalled
>>> plugins.  My goal is to be able to more easily manage geographically
>>> separated cluster members and to quickly add or reinitialize nodes.
>>>
>>> I've been having trouble getting started as I receive HTTP 401
>>> responses when installing remote plugins using the admin interface,
>>> even with security turned off on the maven-repo URL.  I can list the
>>> contents of the remote server's repository, but not install plugins.
>>
>> That's pretty odd.  Can you show the urls being used?  You should be
>> able to check that it's working with a browser.
>>
>>>
>>>
>>> My question is:  Is using the GeronimoAsMavenServlet even the  
>>> correct
>>> approach to pull-based configuration?  How have others implemented
>>> configuration pulling?  Any advice would be greatly appreciated.
>>
>> If you use a geronimo server as the plugin repo then
>> GeronimoAsMavenServlet is the correct approach.  However, if I were  
>> you
>> I would give significant consideration to using nexus as the plugin
>> repo.  I think you will have a much easier time integrating this  
>> with a
>> reasonable build/qa process.  In particular, if you build the plugins
>> using maven with the car-maven-plugin, you can set the distribution
>> management repos to be the nexus server and have mvn deploy or mvn
>> release make the plugin available to the appropriate production  
>> servers.
>
> For satisfying this scenario, how does nexus compare to Archiva, or  
> Artifactory?
>
> Archiva: http://archiva.apache.org/
> Artifactory: http://www.jfrog.org/products.php

I only have experience with nexus and it's worked great for me.  I'm  
not thrilled with the license.  I haven't actually looked but have a  
strong impression that it has a lot more/better features than the  
older managers.

>
>
>
>>
>> I hope you are also aware of the plugin-based clustering/farming  
>> support
>> that may provide the features you need for easy rollout to mutliple
>> servers.  If the existing features there don't exactly match your  
>> needs
>> please work with us to improve this.  For instance IIUC since you
>> indicate your cluster members are geographically separate the current
>> multicast discovery of cluster members may not work for you...  
>> however
>> changing this to a hardcoded set of servers should be pretty easy.   
>> Or
>> perhaps you want a hybrid approach where a bunch of multicast- 
>> connected
>> sub-clusters aggregate to a controller.
>
> I think the desire is to pull down the artifacts, initiated from the  
> end
> geronimo server. So if Geronimo starts up, it can go to the central  
> Maven repo
> and see if it needs to pull down anything for configuration.
>
> The plugin-based farming, from my understanding, does the opposite.

Your understanding is incomplete.  With plugin based farming the  
actual artifacts are pulled by each cluster member from the repository.

> The central
> server pushes out the new artifacts to the end web servers. And  
> perhaps this
> introduces a few possibly undesired circumstances:
>
> 1. Centrally pushed out, all servers receive the updates at one  
> time, not
> staggering the updates. Unless you put the servers into multiple  
> groups so that
> each group can receive updates at different times. But that is more  
> administration.
> 2. If a server is offline when the push-out occurs, it is out of  
> date when it
> comes back online. Some kind of re-sync has to happen.
>
> If the end geronimo server does a pull on start-up, then it will  
> always be in
> sync at run time. If we know what triggers the pull, an  
> administrator can
> program this into a distributed command (like Rio, or RHN Satellite  
> command) to
> tell the server to sync itself.

Plugin based farming does pretty much this administration step.  The  
admin server keeps (in a db) plugins, plugin lists, clusters and  
plugin-list to plugin and cluster to plugin list associations.  It  
listens on a multicast address.  When a cluster member starts up it  
starts a heartbeat ping on that multicast address.  When the admin  
server recognizes a new cluster member it sends it a list of all the  
plugins that are supposed to be installed on it.  The cluster member  
then installs all the missing plugins on the list.

If you don't like multicast you have to figure out some other way for  
the cluster members to find the admin server, such as by telling it.   
Then when the admin server fails and you have to move it you need a  
way to tell all the cluster members to look elsewhere.  I know  
multicast is often frowned on but I couldn't think of a plausible  
alternative that seemed like it would actually work.  If you have any  
ideas I'd love to hear them.

If you don't have any need for dynamic plugin administration but are  
happy to kill, reinstall, and restart a cluster member whenever the  
plugins change then you could do something pretty easily with gshell  
to start the server and install a list of plugins on it.... you can  
script this very easily so you'd only be shipping a script to the  
cluster members.

thanks
david jencks

>
>
> -RG
>
>
>>
>> thanks
>> david jencks
>>
>>>
>>> Thank you,
>>> Chance
>


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