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HDFS >> mail # dev >> Re: Plans of moving towards JDK7 in trunk


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Re: Plans of moving towards JDK7 in trunk
On 21 June 2014 08:01, Andrew Wang <[EMAIL PROTECTED]> wrote:

I'm saying that we'd replace hadooop 2.6 with a 3.x release that, along
with the 2.6 changes, ups the java version and the JARs and dependencies
which we are frozen with in Hadoop 2.x

this issue of dependencies may not be so visible in hadoop's own codebase,
but when you write any downstream project, the majority of the xml
<clauses> in your POM file is about excluding stuff Hadoop pulls in. I've
been quietly trying to address this at HADOOP-9991, but we've reached the
limit of what can get in.

I'd be happy enough with the original "Stata Plan": a release of Hadoop 2.x
that says "java 7 + new libs", but given we've committed to not doing that,
releasing a Hadoop 3 stating that lets us get a hadoop with a modern set of
underpinnings out in 2014
it'll be > 1 year for 2.x to 3,

And to be realistic, the move to java 8+ across the entire hadoop stack
will probably take 1y too.
branch 2 would be frozen and tell everyone "move to java 7+", everything
downstream gets updated binaries and a chance to move forwards.

There's another issue, which is one Alejandro highlit:

From: Alejandro Abdelnur <[EMAIL PROTECTED]>
Date: 10 April 2014 10:30
Subject: Re: Plans of moving towards JDK7 in trunk
To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
A bit of a different angle.

As the bottom of the stack Hadoop has to be conservative in adopting
things, but it should not preclude consumers of Hadoop (downstream projects
and Hadoop application developers) to have additional requirements such as
a higher JDK API than JDK6.

Hadoop 2.x should stick to using JDK6  API
Hadoop 2.x should be tested with multiple runtimes: JDK6, JDK7 and
eventually JDK8
Downstream projects and Hadoop application developers are free to require
any JDK6+ version for development and runtime.

Hadoop 3.x should allow using JDK7 API, bumping the minimum runtime
requirement to JDK7 and be tested with JDK7 and JDK8 runtimes.
The minimum version of Java that Hadoop mandates is going to be the minimum
version of Java that the entire stack has to adopt, and the minimum version
of Java that has to be run in the datacentre.

I wonder about how easily it will be for us all to go to the big hadoop
sites and say "java 8+ only", as well as to all those Hadoop projects that
want to run on java 7 and say "upgrade time". I think we'll hit a lot of
inertia -and, to be fair- it's due to Hadoop core's long-standing support
for Java 6. If Hadoop 2.x had always been java7+ it would be simpler, but
we all know the trauma of getting hadoop 2.2 out the door and our lack of
enthusiasm for any major dependency updates apart from the protobuf one.

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