[jboss-as7-dev] subsytem interdependency

[Thomas Diesler]

We are talking about subsystem foo being able to handle OSGi 
deployments. The umbrella issue is AS7-5051 
<https://issues.jboss.org/browse/AS7-5051> it is for example already 
possible to put OSGi metadata in your WAR (which makes it a Bundle) and 
deploy that onto JBossWeb. Large webapps can be modularized in a 
standard way and use the OSGi service model to react dynamically to 
service availability. For example a webapp may provide payment 
functionality and choose to delegate that to OSGi service. Each payment 
method (i.e. visa, paypal, etc) could be implemented by a separate 
bundle which registers a payment service. At any time payment services 
can be added/removed/updated - the webapp would react accordingly.

Another benefit of deploying a webapp as Bundle is the OSGi Bundle 
Lifecycle. From the management console you can start/stop the webapp 
(without doing the full deploy/undeploy cycle). This would change the 
availability of the web context.

For this to work the web subsystem has to know whether it is dealing 
with an OSGi bundle deployment. The module is setup by the OSGi layer 
and not by the web subsystem alone. Currently, we only need to add a few 
DUPs and go some different code paths in the web DUPs. See [AS7-5052] 
Allow WAR deployments as OSGi bundles 
<https://github.com/tdiesler/jboss-as/commit/746a95780c916d39ca2fd6be253fa97941b0a299>. 


The general idea is that the Module that is associated with a deployment 
unit may be provided by the OSGi layer. Further DU processing should not 
need to care how the module got created. In case of an OSGi module 
dependency resolution is governed by the OSGi resolver - the thing that 
guarantees to for consistent class spaces.

cheers
-thomas

On 07/12/2012 03:55 PM, Bill Burke wrote:
> Just curious,
>
> Are you talking about deployed application EJBs, WARs, etc?  or the
> actual subsystem modules themselves?  For the former, why do the
> subsystems need to know about OSGi as it pertains to application
> deployments?  Wouldn't OSGi class scoping metadata be handled at the
> JBoss MOdules level?  For the latter, why would subsystems need to
> integrate with OSGi when we already have a kernel model and a class
> scoping project (jboss modules)?
>
> On 7/11/12 12:16 PM, Thomas Diesler wrote:
>> If there is no recommended alternative I would add optional dependencies
>> to integration modules to the osgi subsystem.
>>
>> On 07/11/2012 05:22 PM, Thomas Diesler wrote:
>>> The poor man's approach could be to promote the org.osgi.core and and
>>> some org.osgi.service APIs to core modules similar to javax.*
>>>
>>>
>>> On 07/11/2012 05:14 PM, Thomas Diesler wrote:
>>>> Folks,
>>>>
>>>> related to [web,ejb,cdi,etc]/osgi integration an issue came up whereby
>>>> those ee subsystems don't want to have a dependency on osgi because osgi
>>>> is not a core component of the server. Likewise, osgi should not have a
>>>> dependency on these ee subsystems because it may be configured to run
>>>> independently.
>>>>
>>>> More general if foo and bar are both optional subsystems where do we put
>>>> the code that integrates foo and bar. foo-bar integration might require
>>>> to add a some DUPs. How are these registered?
>>>>
>>>> cheers
>>>> -thomas
>>>>

-- 
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Thomas Diesler
JBoss OSGi Lead
JBoss, a division of Red Hat
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