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https://issues.apache.org/jira/browse/HDFS-6764?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Daryn Sharp updated HDFS-6764:
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Attachment: Screen Shot 2014-07-28 at 11.12.06 AM.png
Darker colors are the raw data of heartbeats per 0.5s. The lighter lines are a
rolling 1s average which makes the rhythmic behavior of the active (light blue)
easier to see.
> 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
> Attachments: Screen Shot 2014-07-28 at 11.12.06 AM.png
>
>
> 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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