[jira] [Commented] (ZOOKEEPER-1879) improve the correctness checking of txn log replay

["Patrick Hunt (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-1879?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13896983#comment-13896983 ] 

Patrick Hunt commented on ZOOKEEPER-1879:
-----------------------------------------

I've been thinking about this for a bit. I was hoping it would be simple and we could just add it to ZOOKEEPER-1573, however I'm not sure. In particular we would need to handle the case where the child/parent znode were added/removed multiple times. A simple check is probably not going to be good enough? We should probably think about it a bit to make sure we handle all the various cases.

> improve the correctness checking of txn log replay
> --------------------------------------------------
>
>                 Key: ZOOKEEPER-1879
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1879
>             Project: ZooKeeper
>          Issue Type: Improvement
>          Components: server
>    Affects Versions: 3.4.6, 3.5.0
>            Reporter: Patrick Hunt
>             Fix For: 3.4.7, 3.5.0
>
>
> In ZOOKEEPER-1573 we decided to fix an issue by relaxing some of the checking. Specifically when the sequence of txns is as follows:
> * zxid 1: create /prefix/a
> * zxid 2: create /prefix/a/b
> * zxid 3: delete /prefix/a/b
> * zxid 4: delete /prefix/a
> the log may fail to replay.
> We addressed this by relaxing a check, which is essentially invalid for this case, but is important in finding corruptions of the datastore.
> We should add this check back with proper validation of correctness.



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