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Posted to hdfs-issues@hadoop.apache.org by "Arpit Agarwal (JIRA)" <ji...@apache.org> on 2016/09/14 21:35:20 UTC
[jira] [Comment Edited] (HDFS-10301) BlockReport retransmissions
may lead to storages falsely being declared zombie if storage report
processing happens out of order
[ https://issues.apache.org/jira/browse/HDFS-10301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15491507#comment-15491507 ]
Arpit Agarwal edited comment on HDFS-10301 at 9/14/16 9:34 PM:
---------------------------------------------------------------
I don't think it is safe to remove storages (and hence block replicas from memory) when the NameNode doesn't have up to date block replica state because the block->storage mapping on the NameNode can be stale e.g. due to disk balancer moving replicas; or due to the way VolumeChoosingPolicy picks storages for new blocks.
was (Author: arpitagarwal):
I don't think it is safe to remove storages (and hence blocks) when the NameNode doesn't have up to date block replica state because the block->storage mapping on the NameNode can be stale e.g. due to disk balancer moving replicas; or due to the way VolumeChoosingPolicy picks storages for new blocks.
> 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-10301.012.patch, HDFS-10301.013.patch, HDFS-10301.014.patch, HDFS-10301.branch-2.7.patch, HDFS-10301.branch-2.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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