[wildfly-dev] Management Parser Versioning

Brian Stansberry brian.stansberry at redhat.com
Tue Apr 28 12:18:04 EDT 2015 

Thanks. That test is specifically checking that the standard configs are 
using the latest xsd, so yeah, it will fail whenever a core snapshot 
bumps the xsd versions. I was hoping it was some static thing we could 
make smarter, but it seems not.

A hack would be to make the test more lenient if system prop 
version.org.wildfly.core ends with "-SNAPSHOT". The PR to update core 
would still need to fix the full configs, but that's less of a problem.

On 4/28/15 10:44 AM, Darran Lofthouse wrote:
> 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.
>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> wildfly-dev mailing list
>>>>>>>>> wildfly-dev at lists.jboss.org
>>>>>>>>> https://lists.jboss.org/mailman/listinfo/wildfly-dev
>>>>>>>>>
>>>>>>>>
>>>>>>>>
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>>>>>>
>>>>>>
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-- 
Brian Stansberry
Senior Principal Software Engineer
JBoss by Red Hat

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