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From Andrew Wang <andrew.w...@cloudera.com>
Subject Re: DISCUSS: Hadoop Compatability Guidelines
Date Thu, 07 Sep 2017 18:47:34 GMT
There's also the DataNode data directory layout. FS edit logs should also
be included if we're including the fsimage.

Historically we've bumped these in minor and major releases, though I'm not
sure whether precedent supports the practice. It means you can't downgrade,
and features that need metadata changes are often also destabilizing. DN
layout version upgrades are also very time intensive, since it needs to
hardlink all the blocks.

I don't think we can change this policy in the next week, but it's
something to consider post-beta1. Now that we have xattrs, there's less
need for metadata layout changes. If we revive the feature flags effort,
then there's even less need.

Cheers,
Andrew

On Thu, Sep 7, 2017 at 11:13 AM, Daniel Templeton <daniel@cloudera.com>
wrote:

> Good point.  I think it would be valuable to enumerate the policies around
> the versioned state stores.  We have the three you listed. We should
> probably include the HDFS fsimage in that list.  Any others?
>
> I also want to add a section that clarifies when it's OK to change the
> visibility or audience of an API.
>
> Daniel
>
>
> On 9/5/17 11:04 AM, Arun Suresh wrote:
>
>> Thanks for starting this Daniel.
>>
>> I think we should also add a section for store compatibility (all state
>> stores including RM, NM, Federation etc.). Essentially an explicit policy
>> detailing when is it ok to change the major and minor versions and how it
>> should relate to the hadoop release version.
>> Thoughts ?
>>
>> Cheers
>> -Arun
>>
>>
>> On Tue, Sep 5, 2017 at 10:38 AM, Daniel Templeton <daniel@cloudera.com>
>> wrote:
>>
>> Good idea.  I should have thought of that. :)  Done.
>>>
>>> Daniel
>>>
>>>
>>> On 9/5/17 10:33 AM, Anu Engineer wrote:
>>>
>>> Could you please attach the PDFs to the JIRA. I think the mailer is
>>>> stripping them off from the mail.
>>>>
>>>> Thanks
>>>> Anu
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On 9/5/17, 9:44 AM, "Daniel Templeton" <daniel@cloudera.com> wrote:
>>>>
>>>> Resending with a broader audience, and reattaching the PDFs.
>>>>
>>>>> Daniel
>>>>>
>>>>> On 9/4/17 9:01 AM, Daniel Templeton wrote:
>>>>>
>>>>> All, in prep for Hadoop 3 beta 1 I've been working on updating the
>>>>>> compatibility guidelines on HADOOP-13714.  I think the initial doc
is
>>>>>> more or less complete, so I'd like to open the discussion up to the
>>>>>> broader Hadoop community.
>>>>>>
>>>>>> In the new guidelines, I have drawn some lines in the sand regarding
>>>>>> compatibility between releases.  In some cases these lines are more
>>>>>> restrictive than the current practices.  The intent with the new
>>>>>> guidelines is not to limit progress by restricting what goes into
a
>>>>>> release, but rather to drive release numbering to keep in line with
>>>>>> the reality of the code.
>>>>>>
>>>>>> Please have a read and provide feedback on the JIRA.  I'm sure there
>>>>>> are more than a couple of areas that could be improved.  If you'd
>>>>>> rather not read markdown from a diff patch, I've attached PDFs of
the
>>>>>> two modified docs.
>>>>>>
>>>>>> Thanks!
>>>>>> Daniel
>>>>>>
>>>>>>
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