Regarding JDK7, we have at least one jira I'm aware of proposing several improvements that we can make in our code by using new JDK7 APIs.
https://issues.apache.org/jira/browse/HADOOP-9590 If anyone wants to repurpose this as a master JDK7 enhancement jira and start cataloging additional improvement ideas for using JDK7 APIs, please feel free. The reluctance I've heard around JDK7 mostly relates to testing and compatibility across ecosystem components. If there are success stories around large-scale Hadoop system test suites executed with JDK7, then that could help build confidence. For compatibility, I think this effectively means that Hadoop, HDFS, YARN and MapReduce have to wait until after all downstream ecosystem projects finish their upgrades to JDK7. Chris Nauroth Hortonworks http://hortonworks.com/ On Fri, Mar 28, 2014 at 11:04 AM, Steve Loughran <ste...@hortonworks.com>wrote: > On 28 March 2014 17:00, Sandy Ryza <sandy.r...@cloudera.com> wrote: > > > My understanding is that unfortunately we're stuck with these for the > rest > > of 2.x, because changing them could break jobs that rely on them. For > jobs > > that want to use newer versions, the recommendation is to use > > mapreduce.user.classpath.first or turn on classpath isolation with > > mapreduce.job.classloader. > > > > > If you look at the compatibility statement of hadoop it makes clear there > are no guarantees about dependencies and especially transitive ones. > > > http://hadoop.apache.org/docs/r2.3.0/hadoop-project-dist/hadoop-common/Compatibility.html#Java_Classpath > > That is not an accident -any statement of stability would risk painting us > into a corner and never able to update anything. It also allowed us to ship > hadoop 2.2 without doing a rush update of every dependency -that would only > have caused chaos and delays. Protubf -> 2.5 was enough -and that was done > because it was even worse than guava in terms of compatibility policy. > > The issue goes beyond MR as YARN apps pick up the core binaries, so are > constrained by what comes in hadoop/lib. hdfs/lib and yarn/lib. most of > which is pretty dated. > > and if you have an app like hbase or accumulo, with more current > dependencies, you have to play games excluding all of hadoop's > dependencies. But even that doesn't help with Guava, because it is so > aggressive about retiring classes and methods. > > for the sake of our own code and more modern apps, I'm in favour of > gradually rolling out updates that don't break things, force a move to > java7 or require changes to the source. > > -- > CONFIDENTIALITY NOTICE > NOTICE: This message is intended for the use of the individual or entity to > which it is addressed and may contain information that is confidential, > privileged and exempt from disclosure under applicable law. If the reader > of this message is not the intended recipient, you are hereby notified that > any printing, copying, dissemination, distribution, disclosure or > forwarding of this communication is strictly prohibited. If you have > received this communication in error, please contact the sender immediately > and delete it from your system. Thank You. > -- CONFIDENTIALITY NOTICE NOTICE: This message is intended for the use of the individual or entity to which it is addressed and may contain information that is confidential, privileged and exempt from disclosure under applicable law. If the reader of this message is not the intended recipient, you are hereby notified that any printing, copying, dissemination, distribution, disclosure or forwarding of this communication is strictly prohibited. If you have received this communication in error, please contact the sender immediately and delete it from your system. Thank You.
