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From "Michael Han (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (ZOOKEEPER-1675) Make sync a quorum operation
Date Mon, 12 Aug 2019 17:03:00 GMT

     [ https://issues.apache.org/jira/browse/ZOOKEEPER-1675?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Michael Han reassigned ZOOKEEPER-1675:

    Assignee: Michael Han

> 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
>            Assignee: Michael Han
>            Priority: Major
> 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, the recent operations committed
by L2 will not be flushed to F so a subsequent read on F will not see 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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