[jira] [Commented] (HDFS-10220) A large number of expired leases can make namenode unresponsive and cause failover

["Mingliang Liu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDFS-10220?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15367292#comment-15367292 ] 

Mingliang Liu commented on HDFS-10220:
--------------------------------------

Thanks for the explanation. I think the wiki page is stale and we should fix this after confirmation.

> A large number of expired leases can make namenode unresponsive and cause failover
> ----------------------------------------------------------------------------------
>
>                 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
>             Fix For: 2.8.0, 3.0.0-alpha1
>
>         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, HADOOP-10220.007.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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