[wildfly-dev] Management Model: Squatter Resources

[David M. Lloyd]

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
>

-- 
- DML