[jira] [Commented] (ZOOKEEPER-1036) send UPTODATE to follower until a quorum of servers synced with leader

["Camille Fournier (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-1036?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13012607#comment-13012607 ] 

Camille Fournier commented on ZOOKEEPER-1036:
---------------------------------------------

The leader will not start responding to client requests from followers until a quorum of followers has ACKed for the leader's zxid so this is not a problem.

> send UPTODATE to follower until a quorum of servers synced with leader
> ----------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-1036
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1036
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: server
>            Reporter: jiangwen wei
>
> 1. current process
> when leader fail, a new leader will be elected, followers will sync with the
> new leader.
> After synced, leader send UPTODATE to follower.
> 2. a corner case
> but there is a corner case, things will go wrong.
> suppose message M only exists on leader, after a follower synced with
> leader, the client connected to the follower will see M.
> but it only exists on two servers, not on a quorum of servers. If the new
> leader and the follower failed, message M is lost, but M is already seen by
> client.
> 3. one solution
> So I think UPTODATE  can be sent to follower only when a quorum of server
> synced with the leader.

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