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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7707) Edit log corruption due to delayed block removal again
Date Tue, 03 Feb 2015 15:29:35 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7707?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14303443#comment-14303443
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Kihwal Lee commented on HDFS-7707:
----------------------------------

If snapshot is not involved, the parent of the file inode will be null, so the existing check
should work. Your test case also reproduces the corruption only when snapshot is used. So
it looks like your approach is correct. When walking up the tree for deletion check, it should
look up the child with the same inode id. Since look up is only possible symbolically, the
id needs to be compared if there is a hit.  I will spend a bit more time on this.



> Edit log corruption due to delayed block removal again
> ------------------------------------------------------
>
>                 Key: HDFS-7707
>                 URL: https://issues.apache.org/jira/browse/HDFS-7707
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 2.6.0
>            Reporter: Yongjun Zhang
>            Assignee: Yongjun Zhang
>         Attachments: HDFS-7707.001.patch, HDFS-7707.002.patch, reproduceHDFS-7707.patch
>
>
> Edit log corruption is seen again, even with the fix of HDFS-6825. 
> Prior to HDFS-6825 fix, if dirX is deleted recursively, an OP_CLOSE can get into edit
log for the fileY under dirX, thus corrupting the edit log (restarting NN with the edit log
would fail). 
> What HDFS-6825 does to fix this issue is, to detect whether fileY is already deleted
by checking the ancestor dirs on it's path, if any of them doesn't exist, then fileY is already
deleted, and don't put OP_CLOSE to edit log for the file.
> For this new edit log corruption, what I found was, the client first deleted dirX recursively,
then create another dir with exactly the same name as dirX right away.  Because HDFS-6825
count on the namespace checking (whether dirX exists in its parent dir) to decide whether
a file has been deleted, the newly created dirX defeats this checking, thus OP_CLOSE for the
already deleted file gets into the edit log, due to delayed block removal.
> What we need to do is to have a more robust way to detect whether a file has been deleted.



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