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From Steve Loughran <ste...@hortonworks.com>
Subject Re: symlink support in Hadoop 2 GA
Date Wed, 18 Sep 2013 12:45:38 GMT
On 18 September 2013 12:53, Alejandro Abdelnur <tucu@cloudera.com> wrote:

> On Wed, Sep 18, 2013 at 11:29 AM, Steve Loughran <stevel@hortonworks.com
> >wrote:
> > I'm reluctant for this as while delaying the release, because we are
> going
> > to find problems all the way up the stack -which will require a
> > choreographed set of changes. Given the grief of the protbuf update, I
> > don't want to go near that just before the final release.
> >
> Well, I would use the exact same argument used for protobuf (which only
> complication was getting protoc 2.5.0 in the jenkins boxes and communicate
> developers to do the same, other than that we didn't hit any other issue
> AFAIK) ...

protobuf was traumatic at build time, as I recall because it was neither
forwards or backwards compatible. Those of us trying to build different
branches had to choose which version to have on the path, or set up scripts
to do the switching. HBase needed rebuilding, so did other things. And I
still have the pain of downloading and installing protoc on all Linux VMs I
build up going forward, until apt-get and yum have protoc 2.5 artifacts.

This means it was very painful for developer, added a lot of late breaking
pain to the developers, but it had one key feature that gave it an edge: it
was immediately obvious where you had a problem as things didn't compile or
classload without linkage problems. No latent bugs, unless protobuf 2.5 has
them internally -for which we have to rely on google's release testing to
have found.

That is a lot simpler to regression test than adding any new feature to
HDFS and seeing what breaks -as that is something that only surfaces out in
the field. Which is why I think it's too late in the 2.1 release timetable
to add symlinks. We've had a 2.1-beta out there, we've got feedback. Fix
those problems that are show stoppers, but don't add more stuff. Which is
precisely why I have not been pushing in any of my recent changes. I may
seem ruthless arguing against symlinks -but I'm not being inconsistent with
my own commit history. The only two things I've put in branch-2.1 since
beta-1 were a separate log for the Configuration deprecation warnings and a
patch to the POM for a java7 build on OSX: and they weren't even my patches.


(One of these days I should volunteer to be the release manager and it'll
be obvious that Arun is being quite amenable to all the other developers)

> IMO, it makes more sense to do this change during the beta rather than when
> GA. That gives us more flexibility to iron out things if necessary.
I'm arguing this change can go into the beta of the successor to 2.1 -not

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