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Showing posts from March, 2015

HDFS Client Configs for talking to HA Hadoop NameNodes

One more simple thing, that had relatively scarce documentation out on the Internet.

As you might know, Hadoop NameNodes finally became HA in 2.0. The HDFS client configuration, which is already a little bit tedious, became more complicated.

Traditionally, there were two ways to configure a HDFS client (lets stick to Java)


Copy over the entire Hadoop config directory with all the xml files, place it somewhere in the classpath of your app or construct a Hadoop Configuration object by manually adding in those files.Simply provide the HDFS NameNode URI and let the client do the rest. 
        Configuration conf = new Configuration(false);
        conf.set("fs.default.name", "hdfs://localhost:8020"); // this is deprecated now
        conf.set("fs.defaultFS", "hdfs://localhost:8020");
        FileSystem fs = FileSystem.get(conf); Most people prefer 2, unless you need way more configs from the actual xml config files, at which point it actually makes …