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https://issues.apache.org/jira/browse/HDFS-4521?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13767677#comment-13767677
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Junping Du commented on HDFS-4521:
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A minor optimization here is cleanup cache only on specific nodes. Filed
HDFS-5208 with a patch, [~cmccabe], would you help to take a look at it?
> invalid network topologies should not be cached
> -----------------------------------------------
>
> Key: HDFS-4521
> URL: https://issues.apache.org/jira/browse/HDFS-4521
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 2.1.0-beta, 1.3.0
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Priority: Minor
> Fix For: 2.1.0-beta, 1.3.0
>
> Attachments: HDFS-4521.001.patch, HDFS-4521.002.patch,
> HDFS-4521.005.patch, HDFS-4521.006.patch, HDFS-4521.008.patch,
> HDFS-4521-branch1.patch
>
>
> When the network topology is invalid, the DataNode refuses to start with a
> message such as this:
> {quote}
> org.apache.hadoop.hdfs.server.protocol.DatanodeProtocol.registerDatanode from
> 172.29.122.23:55886: error:
> org.apache.hadoop.net.NetworkTopology$InvalidTopologyException: Invalid
> network topology. You cannot have a rack and a non-rack node at the same
> level of the network topology.
> {quote}
> This is expected if you specify a topology file or script which puts leaf
> nodes at two different depths. However, one problem we have now is that this
> incorrect topology is cached forever. Once the NameNode sees it, this
> DataNode can never be added to the cluster, since this exception will be
> rethrown each time. The NameNode will not check to see if the topology file
> or script has changed. We should clear the topology mappings when there is
> an InvalidTopologyException, to prevent this problem.
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