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From "Mike Drob (JIRA)" <j...@apache.org>
Subject [jira] [Created] (ACCUMULO-751) Support Wire Compatability
Date Wed, 05 Sep 2012 00:50:07 GMT
Mike Drob created ACCUMULO-751:
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             Summary: Support Wire Compatability
                 Key: ACCUMULO-751
                 URL: https://issues.apache.org/jira/browse/ACCUMULO-751
             Project: Accumulo
          Issue Type: Improvement
          Components: master, tserver
            Reporter: Mike Drob
            Assignee: Eric Newton


With the advent of the HA NameNode in HDFS, the need for planned Hadoop outages has greatly
diminished. I believe that Accumulo should follow suit and eventually allow for no-outage
upgrades.

To support this feature, we would require wire compatibility between different versions so
that the cluster can continue to function in a mixed state. There are already contingencies
for master fail-over and tservers to leave/join the cluster, so I think this is a natural
extension of that code.

To accomplish this for bugfix releases should be trivial. I think it is only necessary to
remove (or relax) the version check that happens when a tserver attempts to join. There are
rarely (never?) changes to the thrift protocol between bugfix releases, so theoretically a
1.4.1 tserver is already compatible with a 1.4.0 master and vice versa.

To maintain compatibility in the face of thrift protocol changes is certainly a harder challenge,
which might be best reserved for a separate ticket.

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