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From "Allen Wittenauer (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4313) ease-of-use: missing fs.default.name should be caught and give a helpful message
Date Tue, 30 Sep 2008 18:39:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4313?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12635805#action_12635805
] 

Allen Wittenauer commented on HADOOP-4313:
------------------------------------------

I was playing around with setting up a single node HDFS.  As part of this experiment, I set
the following in my hadoop-site.xml:

<property>
 <name>hadoop.tmp.dir</name>
 <value>/grid/3/tmp</value>
</property>

<property>
 <name>dfs.name.dir</name>
 <value>/grid/3/hadoop/var/hdfs/name</value>
</property>

<property>
 <name>dfs.data.dir</name>
 <value>/grid/3/hadoop/var/hdfs/data</value>
</property>

clearly forgetting to set fs.default.name and formatting the name node.  Upon running start-all.sh,
i was greeted with:

2008-09-30 18:14:07,565 ERROR org.apache.hadoop.hdfs.server.datanode.DataNode: java.lang.NullPointerException
       at org.apache.hadoop.net.NetUtils.createSocketAddr(NetUtils.java:132)
       at org.apache.hadoop.hdfs.server.namenode.NameNode.getAddress(NameNode.java:130)
       at org.apache.hadoop.hdfs.server.namenode.NameNode.getAddress(NameNode.java:134)
       at org.apache.hadoop.hdfs.server.datanode.DataNode.startDataNode(DataNode.java:235)
       at org.apache.hadoop.hdfs.server.datanode.DataNode.<init>(DataNode.java:205)
       at org.apache.hadoop.hdfs.server.datanode.DataNode.makeInstance(DataNode.java:1199)
       at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:1154)
       at org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataNode.java:1162)
       at org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:1284

with a similar error in the name node log.

This particular NPE is extremely unhelpful in letting someone know they forgot something in
the config.  Also, as a side note the description says:

  <description>The name of the default file system.  Either the
  literal string "local" or a hdfs://host:port for NDFS.</description>

Actually using 'local' reports that it is deprecated.  So we probably shouldn't put that in
the config file as an option. :)


> ease-of-use:  missing fs.default.name should be caught and give a helpful message
> ---------------------------------------------------------------------------------
>
>                 Key: HADOOP-4313
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4313
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: dfs
>            Reporter: Allen Wittenauer
>            Priority: Trivial
>
> Start a new data node and name node with the default fs.default.name can trigger a null
pointer exception with no helpful information as to why.  Instead, it should suggest checking
fs.default.name .

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