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From "Daryn Sharp (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6764) DN heartbeats may become clumped together
Date Mon, 28 Jul 2014 16:11:42 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6764?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14076339#comment-14076339
] 

Daryn Sharp commented on HDFS-6764:
-----------------------------------

This was prominently observed on a HA standby due to HDFS-6763.  Quota recalcs caused all
DNs to heartbeat in the same second.  For a yet unknown reason, HA actives demonstrate a similar
rhythmic clumping heartbeats but not to the same degree.

> DN heartbeats may become clumped together
> -----------------------------------------
>
>                 Key: HDFS-6764
>                 URL: https://issues.apache.org/jira/browse/HDFS-6764
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>            Reporter: Daryn Sharp
>
> DNs send heartbeats on a fixed schedule based on the last time a heartbeat was sent.
 If the NN takes longer to respond than the heartbeat interval then DNs do not sleep until
the next interval.  Instead, another heartbeat is immediately sent and all DNs begin heartbeating
on the same schedule.



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