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From Arun Murthy <...@hortonworks.com>
Subject Re: In hindsight... Re: Thinking ahead to hadoop-2.6
Date Tue, 23 Sep 2014 22:00:46 GMT
Sorry, coming to discussion late.

We all agreed that 2.6 would the *last* release supporting JDK6 and
hadoop-2.7 would drop support for JDK6. We could easily do 2.7 right after
2.6 (maybe with few critical bug-fixes) with the defining feature of 2.7
being *JDK7 only*. I've checked with HBase, Pig and other communities and
they are good with this. I'm thinking I'll follow up 2-3 wks after 2.6 goes
out to release 2.7 which drops JDK6.

We can certainly add support for JDK8 as early as 2.7 if there are
volunteers - clearly we won't make it depend on JDK8 features right away;
since it would still need to support JDK7.

To recap: hadoop-2.7 onwards would be minimum JDK7, with potential support
for JDK8. We can revisit our discussion from a few months ago to discuss
when we *drop* support for JDK7; clearly something I'd like to avoid doing
in haste.


On Thu, Sep 18, 2014 at 8:41 AM, Alejandro Abdelnur <tucu00@gmail.com>

> Am I missing something, or we already agreed that after 2.5 release we
> would move trunk and branch-2 to java 7?
> On Wed, Sep 17, 2014 at 3:33 PM, Travis Thompson <
> travis.r.thompson@gmail.com> wrote:
>> There's actually an umbrella JIRA to track issues with JDK8
>> (HADOOP-11090), in case anyone missed it.
>> At LinkedIn we've been running our Hadoop 2.3 deployment on JDK8 for
>> about a month now with some mixed results.  It definitely works but
>> there are issues, mostly around virtual memory exploding.  The reason
>> we took the jump early is there is a company wide push to move to JDK8
>> ASAP, I suspect this isn't something unique to LinkedIn.   To get this
>> to work with security enabled, we've had to apply patches not even in
>> trunk yet because they break JDK6 compatibility.
>> From my perspective, based on what I've seen and people I've talked
>> to, there is a huge push to move to JDK8 ASAP so it's becoming
>> increasingly urgent to at least get support to run on JDK8.
>> On Wed, Sep 17, 2014 at 9:55 AM, Allen Wittenauer <aw@altiscale.com>
>> wrote:
>> >
>> > On Sep 17, 2014, at 2:47 AM, Steve Loughran <stevel@hortonworks.com>
>> wrote:
>> >>
>> >> I don't agree. Certainly the stuff I got into Hadoop 2.5 nailed down
>> the
>> >> filesystem binding with more tests than ever before.
>> >
>> >         FWIW, based upon my survey of JIRA, there are a lot of unit
>> test fixes that are only in trunk.
>> >
>> >> But I am also aware of large organisations that are still on Java 6.
>> >> Giving a clear roadmap "move to Java 7 now, java 8 in "XX months" can
>> help
>> >> them plan.
>> >
>> >         Planning is a big thing.  That’s one of the reasons why it’d be
>> prudent to start doing 3.0+JDK8 now as well.  Even if April slips, other
>> projects and orgs are already moving to 8.  These people wonder what our
>> plans are so that they can run one JVM.  Right now our answer is ¯\_(ツ)_/¯ .
>> >
>> >         I’m sure I can dig up a user running Hadoop 0.13 because it ran
>> on JDK5.  That doesn’t mean the open source project should stall because
>> certain orgs don’t/can't upgrade.
>> >
>> >>>
>> >>>        Drop the 2.6.0 release, branch trunk, and start rolling a
>> >>> 3.0.0-alpha with JDK8 as the minimum.  2.5.1 becomes the base for all
>> >>> sustaining work.  This gives the rest of the community time to move
>> to JDK8
>> >>> if they haven’t already.  For downstream vendors, it gives a roadmap
>> for
>> >>> their customers who will be asking about JDK8 sooner rather than
>> later.  By
>> >>> the time 3.0 stabilizes, we’re probably looking at April, which is
>> perfect
>> >>> timing.
>> >>>
>> >>>
>> >> That delays getting stuff out too much; if april slips it becomes a
>> long
>> >> time since an ASF release came out.
>> >
>> >         I’m assuming you specifically mean a ‘stable’ release.  If, as
>> everyone seems to be saying, that 3.x doesn’t have that much different than
>> 2.x, doesn’t this mean that 3.x should be stable much quicker than 2.x
>> took?  In other words, if 2.5 is stable and the biggest differences between
>> it and trunk is the majority of code (450+ JIRAs as of yesterday afternoon)
>> that just also happens to be in 2.6, doesn’t it mean 2.6 is also extremely
>> unstable?  (Thus supporting my conjecture that 2.6 is going to be a
>> problematic release?)
>> >
>> >> Saying "you must run on Java 8 for
>> >> this" will only scare people off and hold back adoption of 3.x,
>> leaving 2.5
>> >> as the last release that ends up being used for a while; the new 1.0.4
>> >
>> >         From the outside, trunk looks a lot of 0.21 already.  From what
>> I can tell, there is zero motivation to get it out the door and on a
>> roadmap. Primarily because there is little different between trunk and
>> branch-2.  This is a very dangerous place to be as those few differences,
>> some measured in years old, rot and wither. :(
>> >
>> >> Here's an alternative
>> >>
>> >> -2.6 on java 6, announce EOL for Java 6 support
>> >> -2.7 on Java 7, state that the lifespan of j7 support will be some
>> bounded
>> >> time period (12-18 mo)
>> >> -trunk to build and test on Java 8 in jenkins alongside java 7. For
>> that to
>> >> be useful someone needs to volunteer to care about build failures. are
>> you
>> >> volunteering, Allen?
>> >
>> >         This seems reasonable, except what release should folks who
>> *require* java 8 use? Nightly trunk+patches builds? How do downstream
>> projects test?  Should JDK8 fixes be going into a branch?  (I’m making the
>> assumption that fixes for JDK8 are not backward compatible with JDK7.
>> Hopefully they are, but given our usage of private APIs…)
>> >
>> >         I’ve been approached by a few people over the past month+ if
>> I’d be interested in or will be RM’ing 3.0.  I’m seriously considering it
>> esp given a) it’d be a nice learning experience for me  b) my “day job”
>> makes it practical time-wise c) I seem to be the only one concerned enough
>> about quite a bit of stale code  to get it out the door.
>> >
>> >         FWIW, I’m in the process of moving my test vm to JDK8 to see
>> how bad the damage truly is right now. Based on others, it seems security
>> doesn’t work, which is a pretty big deal.  I can certainly start posting
>> trunk builds on people.apache.org if folks are interested.
>> >
>> >> -we switch trunk to Java 7 NOW. That doesn't mean a rewrite fest going
>> >> through all catch() statements making them multicatch, and the same for
>> >> string case.
>> >
>> >         Yup.  There’s little reason *not* to switch trunk to JDK7 now.


Arun C. Murthy
Hortonworks Inc.

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