Cassandra / Hadoop : No local connection available

If you are trying to run the word_count example in Cassandra Hadoop, and you encounter the following exception:

java.lang.RuntimeException: java.lang.UnsupportedOperationException: no local connection available
at org.apache.cassandra.hadoop.ColumnFamilyRecordReader.initialize(ColumnFamilyRecordReader.java:132)
at org.apache.hadoop.mapred.MapTask$NewTrackingRecordReader.initialize(MapTask.java:418)
at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:620)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:305)
at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:177)
Caused by: java.lang.UnsupportedOperationException: no local connection available
at org.apache.cassandra.hadoop.ColumnFamilyRecordReader.getLocation(ColumnFamilyRecordReader.java:176)
at org.apache.cassandra.hadoop.ColumnFamilyRecordReader.initialize(ColumnFamilyRecordReader.java:113)
... 4 more

Then you have hit a problem with local IP resolution in Java.

Cassandra currently uses the following line to resolve IP addresses;

localAddresses = InetAddress.getAllByName(InetAddress.getLocalHost().getHostAddress());

There are better ways to do this using the NetworkInterface,

http://stackoverflow.com/questions/901755/how-to-get-the-ip-of-the-computer-on-linux-through-java

http://www.jguru.com/faq/view.jsp?EID=790132

But until Cassandra uses that you'll need to make sure that the bit of code above resolves properly by manipulating your /etc/hosts to resolve localhost to match the configuration in Cassandra, which by default is looking for localhost bound to 127.0.0.1.

I submitted a patch for this. If you are having issues, please vote to get the patch accepted.
https://issues.apache.org/jira/browse/CASSANDRA-3211