I think the biggest concern is enterprise users/operators who do not have the authority or access to upgrade hadoop/yarn clusters to java8. As a reference point, apparently CDH 5.3 <https://www.cloudera.com/documentation/enterprise/release-notes/topics/cdh_rn_new_in_cdh_53.html#concept_c1n_bln_tj> shipped with java 8 in December 2014. I would be surprised if such users were active consumers of the dev mailing list, though. Unfortunately there's a bit of a selection bias in this list.
The other concern is if there is guaranteed compatibility between scala and java8 for all versions you want to use (which is somewhat touched upon in the PR). Are you thinking about supporting scala 2.10 against java 8 byte code? See https://groups.google.com/d/msg/druid-user/aTGQlnF1KLk/NvBPfmigAAAJ for the similar discussion that went forward in the Druid community. On Fri, Feb 10, 2017 at 8:47 AM Sean Owen <so...@cloudera.com> wrote: > As you have seen, there's a WIP PR to implement removal of Java 7 support: > https://github.com/apache/spark/pull/16871 > > I have heard several +1s at > https://issues.apache.org/jira/browse/SPARK-19493 but am asking for > concerns too, now that there's a concrete change to review. > > If this goes in for 2.2 it can be followed by more extensive update of the > Java code to take advantage of Java 8; this is more or less the baseline > change. > > We also just removed Hadoop 2.5 support. I know there was talk about > removing Python 2.6. I have no opinion on that myself, but, might be time > to revive that conversation too. >
