In order to inspect work node logs in a Hadoop cluster that is behind a firewall with only SSH access, a browser must be setup for tunneling.
Hadoop MapReduce can write key/value output to HDFS in a variety of formats. Here is how to display them.
This four-part series shows how to pass multiple values from a mapper to a reducer, and from the reducer to output.
Passing Multiple Values in MapReduce Part 1: Strings
Passing Multiple Values in MapReduce Part 2: Custom Writables
Passing Multiple Values in MapReduce Part 3: Maps
Passing Multiple Values in MapReduce Part 4: AVRO
Using the software lifecycle and build tool Maven, you can configure Eclipse for Hadoop development in minutes.
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