[jira] [Commented] (ZOOKEEPER-1573) Unable to load database due to missing parent node

["Flavio Junqueira (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-1573?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13888571#comment-13888571 ] 

Flavio Junqueira commented on ZOOKEEPER-1573:
---------------------------------------------

yes, we should get this in 3.4.6. let me give it a closer look, but ignoring NONODE/NODEEXISTS sounds like the right thing to do.

> Unable to load database due to missing parent node
> --------------------------------------------------
>
>                 Key: ZOOKEEPER-1573
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1573
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: server
>    Affects Versions: 3.4.3, 3.5.0
>            Reporter: Thawan Kooburat
>            Assignee: Vinay
>            Priority: Critical
>             Fix For: 3.4.6, 3.5.0
>
>         Attachments: ZOOKEEPER-1573-3.4.patch, ZOOKEEPER-1573.patch, ZOOKEEPER-1573.patch, ZOOKEEPER-1573.patch, ZOOKEEPER-1573.patch
>
>
> While replaying txnlog on data tree, the server has a code to detect missing parent node. This code block was last modified as part of ZOOKEEPER-1333. In our production, we found a case where this check is return false positive.
> 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 server start capturing snapshot at zxid 1. However, by the time it traversing the data tree down to /prefix, txn 4 is already applied and /prefix have no children. 
> When the server restore from snapshot, it process txnlog starting from zxid 2. This txn generate missing parent error and the server refuse to start up.
> The same check allow me to discover bug in ZOOKEEPER-1551, but I don't know if we have any option beside removing this check to solve this issue.  



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