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From Todd Lipcon <t...@cloudera.com>
Subject Re: Branch for HDFS-1073 and related work
Date Tue, 29 Mar 2011 06:18:20 GMT
I've created this branch "HDFS-1073" as discussed. In this branch there's a
new CHANGES.HDFS-1073.txt file -- please add entries into this file rather
than CHANGES.txt if you commit stuff to the branch. This will simplify our
merges later on, I think. We'll transfer the changes back into CHANGES.txt
and delete this file when we do the final merge into trunk.

I've also created an associated Fix Version on JIRA.

Regarding review process, turnaround time in reviews has made this work
progress slower than I'd like. For example, HDFS-1538 has had patches
available with no comments for several months. Of course, I've had a few
bouts where I've been quite slow to respond to feedback as well -- sorry for
that. This is now my top priority so I should be making rapid progress on
development from here on out.

I agree with Jakob that this is tricky code and deserves thorough review,
and also that it's easier to review small patches than a giant merge. So, I
will make sure that the work going into the branch is associated with
coherent changes, each associated with a JIRA, to aid reviewers in
understanding the changes so much as is practical. But, I think something
closer to commit-then-review will allow us to make progress much faster. As
a compromise, I'll be following the following policy:

- A patch will be uploaded to the JIRA for review like usual
- If another committer provides a +1, it may be committed at that point,
just like usual.
- If no committer provides +1 (or a review asking for changes) within 24
business hours, it will be committed to the branch under "commit then
review" policy.

Of course if any committer feels that code needs to be amended, he or she
should feel free to open a new JIRA against the branch including the review
comments, and they will be addressed before the merge into trunk. And just
like with any branch merge, ample time will be given for the community to
review both the large merge commit as well as the individual historical
commits of the branch, before it goes into trunk.

Thanks!

-Todd

On Mon, Mar 28, 2011 at 9:24 PM, Konstantin Shvachko
<shv.hadoop@gmail.com>wrote:

> +1 for creating a branch.
> Agree with Jakob this should not mean less intensive reviewing.
> --Konstantin
>
> On Mon, Mar 28, 2011 at 4:39 PM, Jakob Homan <jghoman@gmail.com> wrote:
>
> > Doing this work on a branch makes sense.  +1.
> >
> > However, the patches that have been committed so far required
> > extensive review and revision, and in one case, an addendum patch.
> > Additionally, the patches in related JIRAs such as HDFS-1557 and
> > HDFS-1572 have required multiple revisions and corrections.  While
> > it's up to each committer which +1 they're willing to accept, I don't
> > see any harm in keeping our current standards for review, considering
> > the importance and difficulty of this work.  In fact, since moving the
> > work to a branch will also move it off of many reviewers' radar, it
> > may even be reasonable to increase the scrutiny.  Reviewing giant
> > branch merges is difficult and, I believe, more error-prone than
> > reviewing smaller packets of work.  So far these patches have received
> > timely reviews, if this does not turn out to be the case, let other
> > committers know so we can do our part.
> > -jg
> >
> >
> > On Mon, Mar 28, 2011 at 1:40 PM, Dhruba Borthakur <dhruba@gmail.com>
> > wrote:
> > > +1. I think this will be very helpful in moving the design forward
> > quickly.
> > >
> > > -dhruba
> > >
> > >
> > > On Mon, Mar 28, 2011 at 1:14 PM, Todd Lipcon <todd@cloudera.com>
> wrote:
> > >
> > >> Hi all,
> > >>
> > >> I discussed this with a couple folks over the weekend who are involved
> > in
> > >> the project, but wanted to let the dev community at large know:
> > >>
> > >> I'm planning on creating a new SVN branch for HDFS-1073 and its
> > subtasks.
> > >> For those not aware, HDFS-1073 is a rethinking of how the NN, 2NN, and
> > >> BackupNode store images and edit logs on disk. This will help make HA
> > more
> > >> manageable down the line and has a lot of operational benefits as
> > described
> > >> in the JIRA. The "related work" is the addition of transaction IDs to
> > the
> > >> persistent storage of the NN, and some refactoring in the edit log
> > >> subsystem.
> > >>
> > >> The reasoning behind creating a branch is that, since this is a fairly
> > >> large
> > >> change, it is easier to develop through a number of subtasks. But at
> > some
> > >> of
> > >> the intermediate points, various components will be temporarily
> broken.
> > >> Developing on a branch will allow us to make incremental progress
> > without
> > >> worrying about keeping all tests green after every change. We will of
> > >> course
> > >> make sure all tests pass before merging back into trunk. There will
> also
> > be
> > >> another opportunity to review before the merge into trunk. This is the
> > same
> > >> development methodology as was done for the 0.21 Append work and is
> now
> > >> being used for Federation.
> > >>
> > >> Given that there will be another opportunity to review these changes
> > before
> > >> merging into trunk, I would also like to propose that Ivan Kelly be
> > granted
> > >> the ability to "+1" patches on this branch despite not being an HDFS
> > >> committer. Ivan is actively contributing on this project and
> understands
> > >> the
> > >> code well.
> > >>
> > >> Unless there are any objections, I will create this branch and an
> > >> associated
> > >> Fix Version on JIRA tonight.
> > >>
> > >> Thanks!
> > >> -Todd
> > >> --
> > >> Todd Lipcon
> > >> Software Engineer, Cloudera
> > >>
> > >
> > >
> > >
> > > --
> > > Connect to me at http://www.facebook.com/dhruba
> > >
> >
>



-- 
Todd Lipcon
Software Engineer, Cloudera

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