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https://issues.apache.org/jira/browse/ZOOKEEPER-3607?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17058458#comment-17058458
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Jiafu Jiang commented on ZOOKEEPER-3607:
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[~lvfangmin] I don't known if 3.4 is the same with 3.5 and 3.6.
> Potential data inconsistency due to the inconsistency between
> ZKDatabase.committedLog and dataTree in Trunc sync.
> -----------------------------------------------------------------------------------------------------------------
>
> Key: ZOOKEEPER-3607
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-3607
> Project: ZooKeeper
> Issue Type: Bug
> Components: quorum
> Affects Versions: 3.4.14
> Reporter: Jiafu Jiang
> Priority: Critical
>
> I will describe the problem by a detail example.
> 1. Suppose we have three zk servers: zk1, zk2, and zk3. zk1 and zk2 are
> online, zk3 is offline, zk1 is the leader.
> 2. In TRUNC sync, zk1 sends a TRUNC request to zk2, then sends the remaining
> proposals in the committedLog. *When the follower zk2 receives the proposals,
> it applies them directly into the datatree, but not the committedLog.*
> 3. After the data sync phase, zk1 may continue to send zk2 more committed
> proposals, and they will be applied to both the datatree and the committedLog
> of zk2.
> 4. Then zk1 fails, zk3 restarts successfully, zk2 becomes the leader.
> 5. The leader zk2 sends a TRUNC request to zk3, then the remaining proposals
> from the committedLog. But since some proposals, which are from the leader
> zk1 in TRUNC sync(as I describe above), are not in the committedLog, they
> will not be sent to zk3.
> 6. Now data inconsistency happens between zk2 and zk3, since some data may
> exist in zk2's datatree, but not zk3's datatree.
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