Auto groups get created for resources:

• of the same type
• children of the same parent

Can you post your plugin descriptor?

Your plugin descriptor is ok: there is only one resource type definition so resources of this type discovered under the same parent should autogroup.

Consider the "Garbage Collector" type defined in the JMX plugin descriptor.

 <service name="Garbage Collector" discovery="MBeanResourceDiscoveryComponent" class="MBeanResourceComponent"
          description="A garbage collector that collects one or more memory pool.">

    <plugin-configuration>
       <c:simple-property name="objectName" readOnly="true" default="java.lang:type=GarbageCollector,name=%name%"/>
       <c:simple-property name="nameTemplate" readOnly="true" default="{name}"/>
       <c:simple-property name="descriptionTemplate" readOnly="true" default="The {name} Garbage Collector for this VM."/>
       <c:simple-property name="name" type="string" readOnly="true" description="The garbage collector's name"/>
    </plugin-configuration>

    <metric property="CollectionCount"
            measurementType="trendsup"
            displayType="summary"
            description="Number of collections"/>
    <metric property="CollectionTime"
            measurementType="trendsup"
            displayType="summary"
            description="The amount of time spent in collection"
            units="milliseconds"/>
    <metric property="MemoryPoolNames"
            description="The names of the memory pools used by this type of garbage collector"
            displayType="summary"
            dataType="trait"/>
 </service>

</service>

Here's how these services appear under the JVM resource of the RHQ Agent:

An autogroup is created, named "Garbage Collectors".

Would you mind posting a similar screenshot for you Cache services?

Thanks