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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-10220) Namenode failover due to too long loking in LeaseManager.Monitor
Date Tue, 10 May 2016 16:01:13 GMT

    [ https://issues.apache.org/jira/browse/HDFS-10220?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15278334#comment-15278334
] 

Kihwal Lee commented on HDFS-10220:
-----------------------------------

Sorry for being late in the party. 200ms of write locking is an eternity.  Since small delay
in releasing leases is not critical and the check runs roughly every 2 seconds, can we reduce
the limit to something shorter? How long did it take to release 5M in your case? Was logging
inside the write lock slowing things down significantly?  Since the limit is not configurable,
we should make sure the fixed value is reasonable.  The rest of the patch looks good.

> Namenode failover due to too long loking in LeaseManager.Monitor
> ----------------------------------------------------------------
>
>                 Key: HDFS-10220
>                 URL: https://issues.apache.org/jira/browse/HDFS-10220
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>            Reporter: Nicolas Fraison
>            Assignee: Nicolas Fraison
>            Priority: Minor
>         Attachments: HADOOP-10220.001.patch, HADOOP-10220.002.patch, HADOOP-10220.003.patch,
HADOOP-10220.004.patch, HADOOP-10220.005.patch, HADOOP-10220.006.patch, threaddump_zkfc.txt
>
>
> I have faced a namenode failover due to unresponsive namenode detected by the zkfc with
lot's of WARN messages (5 millions) like this one:
> _org.apache.hadoop.hdfs.StateChange: BLOCK* internalReleaseLease: All existing blocks
are COMPLETE, lease removed, file closed._
> On the threaddump taken by the zkfc there are lots of thread blocked due to a lock.
> Looking at the code, there are a lock taken by the LeaseManager.Monitor when some lease
must be released. Due to the really big number of lease to be released the namenode has taken
too many times to release them blocking all other tasks and making the zkfc thinking that
the namenode was not available/stuck.
> The idea of this patch is to limit the number of leased released each time we check for
lease so the lock won't be taken for a too long time period.



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