[wildfly-dev] Management Model: Squatter Resources

[Brian Stansberry]

I'm not so sure that bad idea was yours.

But +1 on getting rid of the existing min/max thing.

On 10/30/14, 8:58 AM, David M. Lloyd wrote:
> Using schema-ish things like min/max was probably a bad idea on my part.
>    After trying to model XML schema in various ways for various reasons
> over the years, I know now that the simpler our rules are, the easier it
> will be to implement a cohesive and useful UX.
>
> IMO any currently unused and un-useful constructs like this that are
> hanging around probably need to be pruned, before someone actually uses
> them and makes everyone's live more difficult. :-)
>
> On 10/30/2014 08:44 AM, Brian Stansberry wrote:
>> No, we don't. That currently would have to be handled in a custom way by
>> the OSH that does the add for any of the children.
>>
>> There are some bits and pieces in the metadata that can help with doing
>> some sort of automated validation (i.e. a currently basically unused
>> max/min child count thing) but I don't think what's there is sufficient.
>>
>> The fact the metadata isn't there means a client like the console
>> couldn't enforce the constraint server side, for a better UX.
>>
>> On 10/30/14, 8:08 AM, David M. Lloyd wrote:
>>> I mean, a single child where there can be many possible types for that
>>> child.
>>>
>>> On 10/30/2014 08:01 AM, David M. Lloyd wrote:
>>>> I think that polymorphism is a new use case for 'squatters'.  I wonder
>>>> if we have any existing code which enforces single children?
>>>>
>>>> On 10/30/2014 05:40 AM, Jeff Mesnil wrote:
>>>>> I’m integrating HornetQ 2.5 in WildFly and I have a new use case for resources that is related to singleton/squatter resources.
>>>>>
>>>>> In HornetQ 2.5 they have completely rewritten the HA configuration. Basically, a server can be configured as live-only, replicated (master, slave, or colocated) or using shared-store (again as a master, slave or colocated).
>>>>>
>>>>> To represent this in the management model, I have added several resources under hornetq-server:
>>>>>
>>>>> /subsystem=messaging/
>>>>>        hornetq-server=*/
>>>>>          ha-policy=live-only
>>>>>          ha-policy=replicated-master
>>>>>          ha-policy=replicated-slave
>>>>>          ha-policy=replicated-colocated
>>>>>          ha-policy=shared-store-master
>>>>>          ha-policy=shared-store-slave
>>>>>          ha-policy=shared-store-colocated
>>>>>
>>>>> I have constraints for this ha-policy resource:
>>>>>        * There can at most one child for this type of resource (no child means no HA). This is enforces during the MODEL stage.
>>>>>        * The child can only be named using one of the 7 values above (i.e. there is no resource definition for ha-policy=*, using any other name would fail)
>>>>>
>>>>> Each ha-policy definition has a different set of attributes. Using an attribute group to represent the HA policy does not seem a good fit as some of them have subresources too.
>>>>>
>>>>> I wonder if that representation fits with our roadmap and whether it can be considered as a singleton (as there can only be one resource of that type among). I have the additional constraints of having only one chile for that type that is not covered by your proposal though.
>>>>>
>>>>> I especially wonder how the console (and to a lesser extent the cli) can deal with this resource.
>>>>>
>>>>> Heiko, is it something that would make sense for the console based on this resource description:
>>>>>
>>>>> [standalone at localhost:9990 hornetq-server=default] ./ha-policy=*:read-resource-description(recursive-depth=1)
>>>>> {
>>>>>          "outcome" => "success",
>>>>>          "result" => [
>>>>>              {
>>>>>                  "address" => [
>>>>>                      ("subsystem" => "messaging"),
>>>>>                      ("hornetq-server" => "default"),
>>>>>                      ("ha-policy" => "replication-colocated")
>>>>>                  ],
>>>>>                  "outcome" => "success",
>>>>>                  "result" => {
>>>>>                      ...
>>>>>                  }
>>>>>              },
>>>>>              {
>>>>>                  "address" => [
>>>>>                      ("subsystem" => "messaging"),
>>>>>                      ("hornetq-server" => "default"),
>>>>>                      ("ha-policy" => "replication-master")
>>>>>                  ],
>>>>>                  "outcome" => "success",
>>>>>                  "result" => {
>>>>>                      ...
>>>>>                  }
>>>>>              },
>>>>>              {
>>>>>                  "address" => [
>>>>>                      ("subsystem" => "messaging"),
>>>>>                      ("hornetq-server" => "default"),
>>>>>                      ("ha-policy" => "shared-store-slave")
>>>>>                  ],
>>>>>                  "outcome" => "success",
>>>>>                  "result" => {
>>>>>                      ...
>>>>>                  }
>>>>>              },
>>>>>              {
>>>>>                  "address" => [
>>>>>                      ("subsystem" => "messaging"),
>>>>>                      ("hornetq-server" => "default"),
>>>>>                      ("ha-policy" => "live-only")
>>>>>                  ],
>>>>>                  "outcome" => "success",
>>>>>                  "result" => {
>>>>>                      ...
>>>>>                  }
>>>>>              },
>>>>>              {
>>>>>                  "address" => [
>>>>>                      ("subsystem" => "messaging"),
>>>>>                      ("hornetq-server" => "default"),
>>>>>                      ("ha-policy" => "shared-store-master")
>>>>>                  ],
>>>>>                  "outcome" => "success",
>>>>>                  "result" => {
>>>>>                      ...
>>>>>                  }
>>>>>              },
>>>>>              {
>>>>>                  "address" => [
>>>>>                      ("subsystem" => "messaging"),
>>>>>                      ("hornetq-server" => "default"),
>>>>>                      ("ha-policy" => "replication-slave")
>>>>>                  ],
>>>>>                  "outcome" => "success",
>>>>>                  "result" => {
>>>>>                      ...
>>>>>                  }
>>>>>              },
>>>>>              {
>>>>>                  "address" => [
>>>>>                      ("subsystem" => "messaging"),
>>>>>                      ("hornetq-server" => "default"),
>>>>>                      ("ha-policy" => "shared-store-colocated")
>>>>>                  ],
>>>>>                  "outcome" => "success",
>>>>>                  "result" => {
>>>>>                      ...
>>>>>                  }
>>>>>              }
>>>>>          ]
>>>>> }
>>>>>
>>>>> jeff
>>>>>
>>>>
>>>
>>
>>
>


-- 
Brian Stansberry
Senior Principal Software Engineer
JBoss by Red Hat