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https://issues.apache.org/jira/browse/HDFS-7923?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14588681#comment-14588681
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Sanjay Radia commented on HDFS-7923:
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bq. This change is really helpful during startup on big clusters. In the past
we have seen restarting all the DNs at once on a several hundred node cluster
bring the NN to its knees.
There is already a random backoff for the initial block report. You can
configure the initial BR backoff time. When that jira was done there was a
proposal to give each DN a different backoff time depending on the number of
outstanding BRs; this enhancement was not done at that time because this
backoff worked very well. For a several hundred node cluster the initial BR
backoff time should be approx 60sec.
> The DataNodes should rate-limit their full block reports by asking the NN on
> heartbeat messages
> -----------------------------------------------------------------------------------------------
>
> Key: HDFS-7923
> URL: https://issues.apache.org/jira/browse/HDFS-7923
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Affects Versions: 2.8.0
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Fix For: 2.8.0
>
> Attachments: HDFS-7923.000.patch, HDFS-7923.001.patch,
> HDFS-7923.002.patch, HDFS-7923.003.patch, HDFS-7923.004.patch,
> HDFS-7923.006.patch, HDFS-7923.007.patch
>
>
> The DataNodes should rate-limit their full block reports. They can do this
> by first sending a heartbeat message to the NN with an optional boolean set
> which requests permission to send a full block report. If the NN responds
> with another optional boolean set, the DN will send an FBR... if not, it will
> wait until later. This can be done compatibly with optional fields.
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