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From "Konstantin Shvachko (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 Wed, 20 Jul 2016 22:01:20 GMT

    [ https://issues.apache.org/jira/browse/HDFS-10301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15386702#comment-15386702
] 

Konstantin Shvachko commented on HDFS-10301:
--------------------------------------------

My general approach to protobuf structures is to minimize changes, especially with redundant
fields.
It is very easy to add fields, as you demonstrated, but you can never remove them.
So add them only if you absolutely must.
But different people can of course have different approaches.

> 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-10301.007.patch, HDFS-10301.008.patch, HDFS-10301.009.patch,
HDFS-10301.01.patch, HDFS-10301.010.patch, HDFS-10301.011.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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