[jira] [Updated] (HDFS-5757) refreshNodes with many nodes at the same time could slow down NN

["Ming Ma (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-5757?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ming Ma updated HDFS-5757:
--------------------------
    Summary: refreshNodes with many nodes at the same time could slow down NN  (was: Decommisson lots of nodes at the same time could slow down NN)

> refreshNodes with many nodes at the same time could slow down NN
> ----------------------------------------------------------------
>
>                 Key: HDFS-5757
>                 URL: https://issues.apache.org/jira/browse/HDFS-5757
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: namenode
>            Reporter: Ming Ma
>            Assignee: Ming Ma
>         Attachments: HDFS-5757.patch
>
>
> Sometimes we need to decomm a whole rack of nodes at the same time. When the decomm is in process; NN is slow.
> The reason is when DecommissionManager checks the decomm status, it acquires namesystem's writer lock and iterates through all DNs; for each DN that is in decommissioning state, it check if replication is done for all the blocks on the machine via blockManager.isReplicationInProgress; for large cluster; the number of blocks on the machine could be big.
> The fix could be to have DecommissionManager check for several decomm-in-progress nodes each time it aquires namesystem's writer lock.



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