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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-3426) Datanode does not start up if the local machines DNS isnt working right and dfs.datanode.dns.interface==default
Date Thu, 26 Feb 2009 17:11:01 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-3426?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Steve Loughran updated HADOOP-3426:
-----------------------------------

    Attachment: hadoop-3426.patch

This update does as suggested -it creates static final cached values

1. errors are logged at info and then, on the second attempt, at ERROR, as it means your network
is really hosed. 

2. The test cases handle the situation of HADOOP-5339, where reverse DNS fails on loopback
addresses

> 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, 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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