[wildfly-dev] Management Parser Versioning

Tue Apr 28 11:44:37 EDT 2015

StandardConfigsXMLValidationUnitTestCase - I have not dug into why it is 
failing but when I update all configs to use version 4 it is back to 
passing.

On 28/04/15 16:23, Brian Stansberry wrote:
> On 4/28/15 10:04 AM, Darran Lofthouse wrote:
>> The following commit covers the WildFly side: -
>>
>> https://github.com/darranl/wildfly/commit/8fc073eb11b71904d6235381ad2d3903ce3241aa
>>
>> One problem with the current split is that as soon as you add a new
>> management schema to core the integration with wildfly is broken
>> immediately as some tests verify we write as version 3 when now we write
>> as version 4.
>>
>
> What tests?
>
> If full tests are validating core concerns, we need to move that
> validation to core, or drop it if it is redundant.
>
>> I would suggest that as soon as we start development on WildFly 10 we
>> create a very fast tag or core with just a few changes, probably just: -
>>     - Bump to Java 8
>>     - This schema version bump in this thread.
>>     - Any other build tweaks needed for Java 8.
>>
>> WildFly can then use the new tag and have the same treatment.
>>
>> Regards,
>> Darran Lofthouse.
>>
>>
>> On 27/04/15 17:14, Darran Lofthouse wrote:
>>> The following commits are now the end result of the re-factoring to
>>> allow a fork on new major versions and also to add version 4.0 of the
>>> schema: -
>>>
>>> https://github.com/wildfly/wildfly-core/compare/f4a07f4e9b41dc59823fea1813f947c67965525a...58faefb1fa830d0193f862da9958b2541aea7dad
>>>
>>> The changes look extensive but TBH the bulk is just moving of existing
>>> code and some duplicate for the fork for 4.
>>>
>>> I have distinct commits to show the steps taken but the key points are: -
>>>
>>> # Split out the model specific parsing from CommonXml into smaller
>>> implementations, this was to allow CommonXml to remain the common base
>>> without still containing version specific parsing.
>>>
>>> # Rework of ManagementXml to be version based and rework the delegate,
>>> the big problem we had was we were looping back on ourselves with static
>>> calls which did not cleanly map to versioned implementations.
>>>
>>> # Moved existing StandalonXml, HostXml, DomainXml, ManagementXml into
>>> 'Legacy' parsers and used existing class to load these on-demand.
>>>
>>> # Forked the legacy parsers to create the version 4 parsers, removed all
>>> version handling so a clean start for 4.
>>>
>>> At this point there is still plenty of parsing code not forked for 4 but
>>> TBH those are all relatively stable and rarely change, StandaloneXml,
>>> HostXml, DomainXml, and ManagementXml on the other hand have changed for
>>> every major version so far.
>>>
>>> Regards,
>>> Darran Lofthouse.
>>>
>>> On 23/04/15 16:37, Darran Lofthouse wrote:
>>>> On 23/04/15 16:32, Brian Stansberry wrote:
>>>>> I don't think I've ever rejected or even questioned a PR because it made
>>>>> a parser tolerant in the way you describe, so I'm fine with being tolerant.
>>>>
>>>> +1 I think the first two rules are what we need to advertise we support,
>>>> after all that is why we have schemas.  The third point is more about
>>>> the requirements being placed on the maintainer of the parser so if your
>>>> XML does not match the schema the best we say is "It may work, it may
>>>> not work and that can change without warning".
>>>>
>>>>> My only caveat is in no way do we have any commitment to be tolerant. If
>>>>> a change is implemented in such a way that the legacy schema parsing is
>>>>> tolerant, then it's tolerant for that change. Some other change may not
>>>>> be implemented that way and the parsing won't be tolerant. So we'll be
>>>>> inconsistent.
>>>>>
>>>>> I'm sure we're already inconsistent in this regard, so that doesn't
>>>>> worry me. The schema defines the rules. If you follow them, you know
>>>>> what you'll get. If you break them, maybe it will work anyway, maybe
>>>>> not. Our only guarantee if you break the rules is you'll either end up
>>>>> with a valid running configuration or we'll fail.
>>>>>
>>>>> On 4/23/15 10:17 AM, Darran Lofthouse wrote:
>>>>>> Thinking about future XML changes, once the parser is forked I think we
>>>>>> can also relax how we add new optional attributes and elements to the
>>>>>> schema.
>>>>>>
>>>>>> As I see it our main commitment is: -
>>>>>>
>>>>>> * XML that is valid according to the schema should parse without error. *
>>>>>>
>>>>>> I say 'should' as I believe in some cases documentation is relied upon
>>>>>> to describe valid combinations.
>>>>>>
>>>>>> * The XML we write must be valid according to the schema. *
>>>>>>
>>>>>> Don't see any justification for not following that one.
>>>>>>
>>>>>> * Parsers can be tolerant to XML that is technically invalid. *
>>>>>>
>>>>>> e.g. we are not big on enforcing sequence ordering.
>>>>>>
>>>>>> So lets say we have a release that contains a 4.0 version of the schema
>>>>>> I think if in version 4.1 of the schema we add an optional attribute or
>>>>>> element we can just add support for that attribute or element to the
>>>>>> existing parse method.
>>>>>>
>>>>>> Of course if the new attribute or element is required then we will need
>>>>>> to switch to something version specific to avoid rejecting previously
>>>>>> valid configuration.
>>>>>>
>>>>>> I know this is a long way off but I only raise this now as I realise
>>>>>> this has already happened where a new optional element has been added to
>>>>>> the schema.  Technically if we were strict about it the code is wrong
>>>>>> but the scenarios where it is going to break for someone are quite
>>>>>> contrived and I think this fits with tolerant parsing and we will
>>>>>> automatically fix on the next write.
>>>>>>
>>>>>> Regards,
>>>>>> Darran Lofthouse.
>>>>>>
>>>>>>
>>>>>> On 22/04/15 13:30, Brian Stansberry wrote:
>>>>>>> That's fine with me.
>>>>>>>
>>>>>>> On 4/22/15 6:20 AM, Darran Lofthouse wrote:
>>>>>>>> Working with the parsers for the core config has become increasingly
>>>>>>>> cryptic, we are now at the point where we have three different major
>>>>>>>> versions which diverge and converge as we work on them.  Most recent
>>>>>>>> changes have resulted in large sections of the config converging for 1.x
>>>>>>>> and 3.x leaving 2.x independent.
>>>>>>>>
>>>>>>>> So that I can add references to Elytron I am starting to add support for
>>>>>>>> version 4.
>>>>>>>>
>>>>>>>> One think that I have learned is that each major version tends to belong
>>>>>>>> to one branch of the codebase, all changes to that version happen on
>>>>>>>> that branch first: -
>>>>>>>>
>>>>>>>>           1.x - Maintained only for EAP
>>>>>>>>           2.x - WildFly 8.x branch
>>>>>>>>           3.x - WildFly Core master branch
>>>>>>>>
>>>>>>>> I would expect if further changes are made to core for WildFly 9
>>>>>>>> releases we will end up with 1.x branch of core and and 4.x version of
>>>>>>>> the schema will be owned by the master branch.
>>>>>>>>
>>>>>>>> To make things less cryptic I am proposing that until we find a better
>>>>>>>> solution for all subsequent major schema versions we just fork the
>>>>>>>> parser and all related classes.
>>>>>>>>
>>>>>>>> This will simplify the code being modified for the upstream development.
>>>>>>>>
>>>>>>>> Forward porting parsing changes will also become a simple copy and paste.
>>>>>>>>
>>>>>>>> For the current cryptic approach I think almost every engineer (and I am
>>>>>>>> finding it really hard to think of exceptions) that has worked in-depth
>>>>>>>> in this area has introduced at least one bug and I don't think the test
>>>>>>>> coverage is high enough to protect against this.
>>>>>>>>
>>>>>>>> Regards,
>>>>>>>> Darran Lofthouse.
>>>>>>>>
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>>>>>>>>
>>>>>>>
>>>>>>>
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>>>>>
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