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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Update of "MovingToJdk7and8" by AndrewWang
Date Fri, 27 Jun 2014 18:41:09 GMT
Dear Wiki user,

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The "MovingToJdk7and8" page has been changed by AndrewWang:
https://wiki.apache.org/hadoop/MovingToJdk7and8?action=diff&rev1=3&rev2=4

Comment:
Add "tucu proposal"

  
  Looking at the big picture, it's reasonable to believe that the users of Apache Hadoop would
be better served by us if we prioritized operational aspects such as rolling upgrades, wire-compatibility
etc. for a couple of years. Since not everyone has moved to hadoop-2 yet, talk of more incompatibility
between hadoop-2/hadoop-3 or between hadoop-3/hadoop-4 within the next 12 months would certainly
be a big issue for users - especially w.r.t rolling upgrades, wire-compat etc.
  
+ Some improvements have also been made to support multiple versions of MR on the same cluster
with their own classpaths. See [[https://issues.apache.org/jira/browse/MAPREDUCE-4421|MAPREDUCE-4421]]
and [[https://issues.apache.org/jira/browse/MAPREDUCE-1700|MAPREDUCE-1700]] for further details.
Furthermore, we also support allowing user applications to use a JDK different from Hadoop
itself - for e.g. HDFS/YARN can run JDK7 while MR applications can run JDK6 if they chose
right now.
  = Proposals =
  
  Listed in roughly chronological order. Not attaching names to keep this disinterested.
@@ -41, +42 @@

   * Drop support for JDK6 in an intermediate branch-2 release, e.g. hadoop-2.8.
   * Drop support for JDK7 in another intermediate branch-2 release, e.g. hadoop-2.15.
  
+ == Proposal D ==
+ 
+  * Choose a branch-2 release to designate as the last JDK6 release, e.g. hadoop-2.y
+  * Set up hadoop-2.y builds with both JDK6 and JDK7
+  * Drop support for JDK6 in branch-2 and trunk
+  * Future branch-2 releases require JDK7+ and can use JDK7 APIs
+  * Discussion of JDK8 is tabled for now
+ 
  = Discussion =
  
  == Proposal A ==
@@ -54, +63 @@

  == Proposal C ==
   * Dropping support for a JDK in a minor release maybe deemed incompatible, so this would
require further discussion.
   * Will continue to support rolling-upgrades, wire protocol compatibility etc.
-  * Features like NOT relying on cluster install of MapReduce binary already help immensely.
See [[https://issues.apache.org/jira/browse/MAPREDUCE-4421|MAPREDUCE-4421]] for further details.
-  * Furthermore, we *already* support allowing user applications to use a JDK different from
Hadoop itself - for e.g. HDFS/YARN can run JDK7 while MR applications can run JDK6 if they
chose right now.
  
+ == Proposal D ==
+  * Seems to have some consensus on common-dev
+  * Not carte blanche to drop JDK support in minor releases
+  * Could do the 2.y release as soon as the upcoming Hadoop 2.5
+  * Same benefits as Proposal C regarding rolling upgrades, wire compat, etc
+ 

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