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Date: Tue, 6 Feb 2007 11:14:05 -0800 (PST)
From: "Andrew McNabb (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Commented: (HADOOP-685) DataNode appears to require DNS name
 resolution as opposed to direct ip mapping
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    [ https://issues.apache.org/jira/browse/HADOOP-685?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12470698 ] 

Andrew McNabb commented on HADOOP-685:
--------------------------------------

We worked around a problem that I think is related.  In /etc/hosts, the default line was "127.0.0.1 localhost.localdomain localhost" because the IP address was assigned by DHCP.  If you ran hostname, it gave the correct name for the host, but 'hostname -f' gave localhost.localdomain because it used /etc/hosts instead of the information from DHCP.

In this situation, Hadoop didn't work because as each machine reported in, they claimed that their hostname was "localhost.localdomain" rather than the actual hostnames.  The jobtracker was confused and didn't work.  We ended up having to manually change /etc/hosts on each machine.

If everything worked with IP addresses instead of hostnames, I think the problem would be fixed.  Anyway, I think this is related to the problem that James Todd brought up.

> DataNode appears to require DNS name resolution as opposed to direct ip mapping
> -------------------------------------------------------------------------------
>
>                 Key: HADOOP-685
>                 URL: https://issues.apache.org/jira/browse/HADOOP-685
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: dfs
>         Environment: osx, ubuntu 6.10b
>            Reporter: James Todd
>         Assigned To: Raghu Angadi
>            Priority: Minor
>
> DataNode appears to require DNS resolution of nodes via the class org.apache.hadoop.net.DNS as opposed being able to use a specified ip.
> as an example, i was not able to set up more then one instance of dfs datanodes on one box using loopback w/ varying ports since DataNode
> resolved the ip of 127.0.0.1 to be "foo.bar" which was then mapped to the dhcp allocated ip of 192.168.0.***, which was not addressable by the
> rest of the dfs cluster (namely namenode).
> while this example is trivial one should be able to use the very same process yet change only the ip's of the nodes and have things work as
> expected.
> it would be nice to not always require nds resolution.

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