[jira] [Created] (ZOOKEEPER-1675) Make sync a quorum operation

["Alexander Shraer (JIRA)" <ji...@apache.org>]

Alexander Shraer created ZOOKEEPER-1675:
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             Summary: Make sync a quorum operation
                 Key: ZOOKEEPER-1675
                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1675
             Project: ZooKeeper
          Issue Type: Bug
    Affects Versions: 3.4.0, 3.5.0
            Reporter: Alexander Shraer


sync + read is supposed to return at least the latest write that completes before the sync starts. This is true if the leader doesn't change, but when it does it may not work. The problem happens when the old leader L1 still thinks that it is the leader but some other leader L2 was already elected and committed some operations. Suppose that follower F is connected to L1 and invokes a sync. Even though L1 responds to the sync, L2 may have already committed new operations so a subsequent read on F will not return these operations. 

To prevent this we should broadcast the sync like updates.

This problem is also mentioned in Section 4.4 of the ZooKeeper peper (but the proposed solution there is insufficient to solve the issue).

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