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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-10301) BlockReport retransmissions may lead to storages falsely being declared zombie if storage report processing happens out of order
Date Tue, 21 Jun 2016 01:43:58 GMT

    [ https://issues.apache.org/jira/browse/HDFS-10301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15340868#comment-15340868
] 

Colin Patrick McCabe commented on HDFS-10301:
---------------------------------------------

The "you" in that sentence was targetted at you, [~shv].  I realized that [~redvine] wrote
the patch, but I spoke imprecisely.  Sorry for the confusion.

bq. This is her first encounter with HDFS community. Let's try to make it pleasant enough
so that she wished to come back and work with us more.

To be honest, I don't think this is a very good newbie JIRA.  It is clearly a very controversial
issue, and it's also a very difficult piece of code with a lot of subtlety.  Since you clearly
have strong opinions about this JIRA, I believe it would be more appropriate for you to post
patches implementing your ideas yourself.  But that is up to you, of course.

> BlockReport retransmissions may lead to storages falsely being declared zombie if storage
report processing happens out of order
> --------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-10301
>                 URL: https://issues.apache.org/jira/browse/HDFS-10301
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 2.6.1
>            Reporter: Konstantin Shvachko
>            Assignee: Vinitha Reddy Gankidi
>            Priority: Critical
>         Attachments: HDFS-10301.002.patch, HDFS-10301.003.patch, HDFS-10301.004.patch,
HDFS-10301.005.patch, HDFS-10301.006.patch, HDFS-10301.01.patch, HDFS-10301.sample.patch,
zombieStorageLogs.rtf
>
>
> When NameNode is busy a DataNode can timeout sending a block report. Then it sends the
block report again. Then NameNode while process these two reports at the same time can interleave
processing storages from different reports. This screws up the blockReportId field, which
makes NameNode think that some storages are zombie. Replicas from zombie storages are immediately
removed, causing missing blocks.



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