[wildfly-dev] Core and subsystem capabilities and requirements

[Jason Greene]

On Jun 23, 2014, at 3:38 PM, Kabir Khan <kabir.khan at jboss.com> wrote:

> 
> On 23 Jun 2014, at 21:31, Jason Greene <jason.greene at redhat.com> wrote:
> 
>> 
>> On Jun 23, 2014, at 2:52 PM, David M. Lloyd <david.lloyd at redhat.com> wrote:
>> 
>>> On 06/23/2014 01:20 PM, Brian Stansberry wrote:
>>>> As we continue with our work splitting the WildFly code base into a core
>>>> repo and then separate repos related to sets of features that we need to
>>>> solidify the contracts between the various features and between features
>>>> and the core.
>>>> 
>>>> I've taken a crack at an initial design document on this: see [1]. We
>>>> also need to do the practical work of identifying the various
>>>> dependencies between our existing subsystems, see [2] for a start on that.
>>>> 
>>>> I'd love to get feedback on this thread regarding the proposed design,
>>>> as well as get direct edits on the [2] doc to flesh out the existing
>>>> relationships.
>>> 
>>> Here is what jumps out at me at first.
>>> 
>>> • I don't understand the reason to not allow optional dependencies on 
>>> capabilities.  It would be of similar implementation complexity to the 
>>> suggested permutation implementation, however it would avoid the problem 
>>> of requiring 2ⁿ permutations for n optional dependencies.
>> 
>> I had the same thought.
> I don’t really understand what you two are getting at here. What would an optional requirement be? I can’t really get my head around “I would like this to be there but I don’t care if it isn’t”.

A good example is, Corba and JTS. Corba needs to be bootstrapped with a special interceptor if JTS is enabled. Corba’s bootstrap could check some HAVE_JTS capability and if present add the interceptor.

>> 
>>> 
>>> • I don't understand the purpose of binding capability identifiers to 
>>> subsystem identifiers.  It seems plausible to have a subsystem provide, 
>>> for example, two capabilities now, but allow for a capability to be 
>>> implemented separately in the future.  A concrete example would be the 
>>> way we ultimately moved Servlet from JBoss Web to Undertow.  Ideally 
>>> we'd only ever depend on the capability, making subsystems completely 
>>> interchangeable.
>> 
>> I think Brian was trying to allow for thirdparty subsystems to potentially collaborate without a global registration (like we have with Phases). In practice I would imagine all of our out of the box subsystems would be using null. Alternatively we could just use some kind of ad-hoc string as a group name or something.
>> 
>> --
>> Jason T. Greene
>> WildFly Lead / JBoss EAP Platform Architect
>> JBoss, a division of Red Hat
>> 
>> 
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> 

--
Jason T. Greene
WildFly Lead / JBoss EAP Platform Architect
JBoss, a division of Red Hat