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List:       hadoop-dev
Subject:    Re: Moving to JDK7, JDK8 and new major releases
From:       Steve Loughran <stevel () hortonworks ! com>
Date:       2014-06-28 15:38:49
Message-ID: CA+4kjVuf63XDgE+s5T2nCdV+S6KM4LrzzsgySEtCpiFrAL5F0g () mail ! gmail ! com
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Guava is a separate problem and I think we should have a separate
discussion "what can we do about guava"? That's more traumatic than a JDK
update, I fear, as the guava releases care a lot less about compatibility.
I don't worry about JDK updates removing classes like "StringBuffer"
because "StringBuilder" is better.


On 27 June 2014 19:26, Andrew Wang <andrew.wang@cloudera.com> wrote:

> Hi all, responding to multiple messages here,
>
> Arun, thanks for the clarification regarding MR classpaths. It sounds like
> the story there is improved and still improving.
>
> However, I think we still suffer from this at least on the HDFS side. We
> have a single JAR for all of HDFS, and our clients need to have all the fun
> deps like Guava on the classpath. I'm told Spark sticks a newer Guava at
> the front of the classpath and the HDFS client still works okay, but this
> is more happy coincidence than anything else. While we're leaking deps,
> we're in a scary situation.
>

very good point.


>
> API compat to me means that an app should be able to run on a new minor
> version of Hadoop and not have anything break. MAPREDUCE-4421 sounds like
> it allows you to run e.g. 2.3 MR jobs on a 2.4 YARN cluster, but what
> should also be possible is running an HDFS 2.3 app with HDFS 2.4 JARs and
> have nothing break. If we muck with the classpath, my understanding is that
> this could break.
>
>
I think this is possible by having the app upload all the JARs...I need to
experiment here myself.

>
>
> Chris, thanks for bringing up the ecosystem. For CDH5, we standardized on
> JDK7 across the CDH stack, so I think that's an indication that most
> ecosystem projects are ready to make the jump. Is that sufficient in your
> mind?
>
>
+1, we've had no complaints about things not working on Java 7. It's been
out a long time. IF you look at our own code, the main thing that broke
were tests -due to junit test case ordering- and not much else.



> For the record, I'm also +1 on the Tucu plan. Is it too late to do this for
> 2.5? I'll offer to help out with some of the mechanics.
>
>

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