[jira] Commented: (HADOOP-1501) Block reports from all datanodes arrive at the namenode within a small band of time

["Raghu Angadi (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-1501?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12506607 ] 

Raghu Angadi commented on HADOOP-1501:
--------------------------------------

Does this mean we could get rid of {{blockReportIntervalBasis}} calculation? Currently it sets the interval to random value between 90-100% of configured interval. It is not necessary anymore.

+1 for current patch.

> Block reports from all datanodes arrive at the namenode within a small band of time
> -----------------------------------------------------------------------------------
>
>                 Key: HADOOP-1501
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1501
>             Project: Hadoop
>          Issue Type: Bug
>          Components: dfs
>            Reporter: dhruba borthakur
>         Attachments: randomBlockReportInterval.patch
>
>
> I have a 2000 node cluster and the block report interval is set to 1 hour. Most block report arrive within a few minutes of one another. For example, I have seen block reports from all 2000 nodes arrive within 5 minutes of one another. This causes CPU overload on the namenode, causing dropped calls in Call queue.
> My proposal is to make the datanode send a block report as soon as the datanode starts. Then, it waits for a random time between 0 to 1 hour (the configured value) before sending the nect block report. From then on, block reports from that datanode are sent once every 1 hour (the configured value).

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