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https://issues.apache.org/jira/browse/ZOOKEEPER-3231?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16736548#comment-16736548
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Brian Nixon commented on ZOOKEEPER-3231:
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It might also make sense to more aggressively delete invalid snapshots (in the 
mode of ZOOKEEPER-3082). If its straightforward to identify and purge such 
files then we won't have to worry about deleting valid snapshots in order to 
preserve invalid snapshots.

>  Purge task may lost data when we have many invalid snapshots.
> --------------------------------------------------------------
>
>                 Key: ZOOKEEPER-3231
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-3231
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: server
>    Affects Versions: 3.5.4, 3.4.13
>            Reporter: Jiafu Jiang
>            Priority: Major
>
> I read the ZooKeeper source code, and I find the purge task use 
> FileTxnSnapLog#findNRecentSnapshots to find snapshots, but the method does 
> not check whether the snapshots are valid.
> Consider a worse case, a ZooKeeper server may have many invalid snapshots, 
> and when a purge task begins, it will use the zxid in the last snapshot's 
> name to purge old snapshots and transaction logs, then we may lost data. 
> I think we should use FileSnap#findNValidSnapshots(int) instead of 
> FileSnap#findNRecentSnapshots in FileTxnSnapLog#findNRecentSnapshots, but I 
> am not sure.
>  



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