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https://issues.apache.org/jira/browse/HADOOP-3426?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12620768#action_12620768
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Owen O'Malley commented on HADOOP-3426:
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I'm worried that using localhost will cause problems, because it only works in
single node cases.
Can't we default instead to the unresolved IP address? As long as we make sure
it isn't 127.0.0.1, it will be useful, even in multi-node clusters.
> Datanode does not start up if the local machines DNS isnt working right and
> dfs.datanode.dns.interface==default
> ---------------------------------------------------------------------------------------------------------------
>
> Key: HADOOP-3426
> URL: https://issues.apache.org/jira/browse/HADOOP-3426
> Project: Hadoop Core
> Issue Type: Bug
> Components: dfs
> Affects Versions: 0.19.0
> Environment: Ubuntu 8.04, at home, no reverse DNS
> Reporter: Steve Loughran
> Assignee: Steve Loughran
> Priority: Minor
> Attachments: hadoop-3426.patch, hadoop-3426.patch
>
>
> This is the third Java project I've been involved in that doesnt work on my
> home network, due to implementation issues with
> java.net.InetAddress.getLocalHost(), issues that only show up on an unamanged
> network. Fortunately my home network exists to find these problems early.
> In hadoop, if the local hostname doesnt resolve, the datanode does not start
> up:
> Caused by: java.net.UnknownHostException: k2: k2
> at java.net.InetAddress.getLocalHost(InetAddress.java:1353)
> at org.apache.hadoop.net.DNS.getDefaultHost(DNS.java:185)
> at org.apache.hadoop.dfs.DataNode.startDataNode(DataNode.java:184)
> at org.apache.hadoop.dfs.DataNode.(DataNode.java:162)
> at org.apache.hadoop.dfs.ExtDataNode.(ExtDataNode.java:55)
> at
> org.smartfrog.services.hadoop.components.datanode.DatanodeImpl.sfStart(DatanodeImpl.java:60)
> While this is a valid option in a production (non-virtual) cluster, if you
> are playing with VMWare/Xen private networks or on a home network, you can't
> rely on DNS.
> 1. In these situations, its usually better to fall back to using "localhost"
> or 127.0.0.1 as a hostname if Java can't work it out for itself,
> 2. Its often good to cache this if used in lots of parts of the system,
> otherwise the 30s timeouts can cause problems of their own.
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