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From "Hairong Kuang (JIRA)" <j...@apache.org>
Subject [jira] Created: (HDFS-1425) Improve NameNode responsiveness by speeding up serving refreshNodes RPC
Date Tue, 28 Sep 2010 21:44:35 GMT
Improve NameNode responsiveness by speeding up serving refreshNodes RPC

                 Key: HDFS-1425
                 URL: https://issues.apache.org/jira/browse/HDFS-1425
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: name-node
    Affects Versions: 0.22.0
            Reporter: Hairong Kuang
            Assignee: Hairong Kuang
             Fix For: 0.22.0

Currently when NN serves the refreshNodes request, it examines every block in the nodes to
be decommissioned and put it in the neededReplication queue, during which a write lock is

In our production cluster when decommissioning 100 nodes, we observed that refreshingNodes
took minutes, during the period NameNode became non responsive.

The proposal is that freshNodes only adds the nodes that need to be decommissioned in a queue
in DecommissionManager and then return. DecommissionManager then takes care of decommissioning
the nodes. This would allow refreshNodes to be returned very quickly.

This also allows us to optimize DecommisionManager. For example, it could sleep when there
is no datanode to be decommissioned while the current code wakes the thread periodically even
when no decommission in progress nodes.

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