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From "Michael Han (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-3056) Fails to load database with missing snapshot file but valid transaction log file
Date Tue, 12 Jun 2018 05:13:00 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-3056?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16509199#comment-16509199
] 

Michael Han commented on ZOOKEEPER-3056:
----------------------------------------

{quote}It's a trade-off between admin time and server side code complexity for sure.
{quote}
I agree. If a snapshot-less use case is rare, it's better to provide an admin ool to force
generate a snapshot before upgrade (or migrate data), to keep a simple server side code. 
{quote}I do believe ZOOKEEPER-2325is a good feature and it would be a shame to set it off
by default.
{quote}
I agree, data consistency is important and even if we decide to provide such a flag, the check
should be enabled by default.

 

> Fails to load database with missing snapshot file but valid transaction log file
> --------------------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-3056
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-3056
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: server
>    Affects Versions: 3.5.3, 3.5.4
>            Reporter: Michael Han
>            Priority: Critical
>
> [An issue|https://lists.apache.org/thread.html/cc17af6ef05d42318f74148f1a704f16934d1253f1472cccc1a93b4b@%3Cdev.zookeeper.apache.org%3E]
was reported when a user failed to upgrade from 3.4.10 to 3.5.4 with missing snapshot file.
> The code complains about missing snapshot file is [here|https://github.com/apache/zookeeper/blob/release-3.5.4/src/java/main/org/apache/zookeeper/server/persistence/FileTxnSnapLog.java#L206]
which is introduced as part of ZOOKEEPER-2325.
> With this check, ZK will not load the db without a snapshot file, even the transaction
log files are present and valid. This could be a problem for restoring a ZK instance which
does not have a snapshot file but have a sound state (e.g. it crashes before being able to
take the first snap shot with a large snapCount parameter configured).



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