[wildfly-dev] Management model attribute groups

[Brian Stansberry]

On 12/9/14, 4:41 PM, Jason Greene wrote:
> This proposal is a great idea. Let’s do it :)
>

I can probably have a branch with the "Proposed Work" bit, excluding the 
CLI ls -l thing, done today or tomorrow. It went quicker than I thought. 
But the more important part is any discussion here. The CLI ls -l thing 
I don't want to code yet because I don't have a strong feeling about 
that solution.

>> On Dec 9, 2014, at 2:00 PM, Brian Stansberry <brian.stansberry at redhat.com> wrote:
>>
>> Off and on we've had discussions around the idea of "attribute groups".
>> We've got some use cases that are crying out for such a thing[1], so I'd
>> like to propose doing something concrete but simple for these for WF 9,
>> ideally in the next month.
>>
>> A big part of my goal here is to ensure that whatever we do doesn't
>> preclude something more advanced in any next generation management
>> stuff, e.g. David's stuff.
>>
>> PART I Concepts
>>
>> 1) What is an attribute group?
>>
>> The "attribute group" concept I propose is simply a collection of
>> attributes associated with the same resource type that are independently
>> configurable but are statically declared to be conceptually related. The
>> group has a name, and members. The name provides a brief indication of
>> the nature of the relationship.
>>
>> The goal is to provide information to the user to help them better
>> understand the relationship between attributes. In particular,
>> management tools could use this information to visually present related
>> attributes together, e.g. in a tab or other grouping widget in the web
>> console.
>>
>> 2) What isn't an attribute group?
>>
>> Something relevant to writes.
>>
>> 3) Why would I use a child resource instead of an attribute group?
>>
>> Because the attributes control a discrete piece of functionality and you
>> need to be able to turn that on or off as a unit. So you add/remove the
>> resource.
>>
>> 4) Why would I use a complex attribute with a bunch of fields instead of
>> n>1 simple attributes in a group.
>>
>> a) Because the attributes control a discrete piece of functionality and
>> you need to be able to turn that off as a unit. So users can undefine
>> the complex attribute.
>>
>> b) Because it's a common use case that modifications to n>1 of the
>> fields should be done atomically and you don't want to force users to
>> use a CLI batch. So you let them use write-attribute and specify the
>> value of all the fields.
>>
>> 5) Why would I use an attribute group instead of a child resource?
>>
>> Because requiring users to add a child resource just to set a bunch of
>> values that are really part of the config of the parent resource forces
>> them to use a CLI batch to correctly configure the parent resource.
>>
>> 6) Why would I use an attribute group instead a complex attribute?
>>
>> Because the various attributes should be independently configurable. In
>> particular, wiping out the config for all of them by simply undefining
>> the complex attribute isn't appropriate.
>>
>> PART II Proposed Work
>>
>> 1) The basics
>>
>> We add a piece of metadata to the read-resource-description output for
>> an attribute. Name is 'attribute-group', value type is ModelType.STRING,
>> value is the name of the group, with 'undefined' allowed.
>>
>> The group is simply the set of attributes that share the same string.
>>
>> To implement this, we add public String
>> AttributeDefinition.getAttributeGroup() and add support for setting it
>> to the relevant Builder. ReadResourceDescriptionHandler outputs the value.
>>
>> 2) XML parsing/marshalling
>>
>> Modify PersistentResourceXMLDescription such that attributes in an
>> attribute group get persisted in their own child element, whose name is
>> the name of the group.
>>
>> PersistentResourceXMLBuilder exposes a setter to allow users to turn
>> this on/off for that resource. Turning it off will allow the addition of
>> attribute group settings for a resource without requiring an immediate
>> corresponding xsd change.
>>
>> 3) Web console
>>
>> HAL can make use of the additional metadata at its leisure, and as it
>> becomes available.
>>
>> 4) Low level management API
>>
>> The output of read-resource and read-resource-description is modified
>> such that attributes are sorted by group name and then by attribute name.
>>
>> 5) CLI
>>
>> I'm not clear on exactly what to do here, but my instinct is the output
>> of the 'ls -l' command should be modified. Probably add a GROUP column
>> to the right and sort the order of attributes by group and then by
>> attribute name.
>>
>> PART III Other possible things to do
>>
>> A :read-attribute-group(name=<groupname>) operation or an
>> "attribute-groups=[<groupname>*]" param to :read-resource, to make it
>> convenient to read a set of attributes without needing to read the
>> entire resource.
>>
>> We could also consider adding an "attribute-groups" section to the
>> read-resource-description output, where a fuller i18n text description
>> of the meaning of the group could be written. If we do this we should
>> probably do it in WF 9 as it will likely add some sort of requirement to
>> subsystem authors that we expose right from the start.
>>
>>
>> If you're still awake, comments as always are appreciated.
>>
>> --
>> Brian Stansberry
>> Senior Principal Software Engineer
>> JBoss by Red Hat
>>
>> [1] For example, the JDKORB pull request at
>> https://github.com/wildfly/wildfly/pull/7008 uses child resources in a
>> number of places where it seems like attribute groups are a better fit.
>>
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>
> --
> Jason T. Greene
> WildFly Lead / JBoss EAP Platform Architect
> JBoss, a division of Red Hat
>


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