[jira] Created: (HDFS-1392) Improve namenode scalability by prioritizing datanode heartbeats over block reports

["dhruba borthakur (JIRA)" <ji...@apache.org>]

Improve namenode scalability by prioritizing datanode heartbeats over block reports
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                 Key: HDFS-1392
                 URL: https://issues.apache.org/jira/browse/HDFS-1392
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: name-node
            Reporter: dhruba borthakur
            Assignee: dhruba borthakur


When a namenode restarts, it gets heartbeats followed by a block reports from the datanodes. The block report processing is heavyweight and can take many many seconds, especially when the number of blocks in each datanode is large. This causes the namenode to not be able to process heartbeats in time, thus leading to "lost heartbeats from datanode". The namenode declares the datanode to be dead and the datanode has to re-send its register/block report all over again. This is a scalability problem.

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