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https://issues.apache.org/jira/browse/HADOOP-3988?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12624378#action_12624378
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Allen Wittenauer commented on HADOOP-3988:
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We recently tried a "new kind" of fail over in our environment. Rather than
having a static IP for the name node, we attempted to use DNS CNAMEs to move
the name node from one node to another. We discovered that the data nodes
continually attempted to contact the old machine even though DNS pointed to the
new machine.
Since we configure a host name in hadoop, I would expect that the data nodes
would at some point drop their cache of the IP and re-resolve. However, this
never happened.
I'd like to see either an option or just the default to be when a name is given
in a configuration file, Hadoop always does a host name resolution on that
entry prior to connection. The operating system should be able to handle the
job of caching any addresses that need to be cached, either through a mechanism
like nscd or through a fully-blooded, local DNS cache.
> The elephant should remember names, not numbers.
> ------------------------------------------------
>
> Key: HADOOP-3988
> URL: https://issues.apache.org/jira/browse/HADOOP-3988
> Project: Hadoop Core
> Issue Type: Bug
> Components: dfs
> Affects Versions: 0.17.2
> Reporter: Allen Wittenauer
>
> The name node and the data node should not cache the resolution of host
> names, as doing so prevents the use of DNS CNAMEs for any sort of fail over
> capability.
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