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Hadoop MapReduce v2 Cookbook - Second Edition by Thilina Gunarathne

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Implementing a custom Hadoop key type

The instances of Hadoop MapReduce key types should have the ability to compare against each other for sorting purposes. In order to be used as a key type in a MapReduce computation, a Hadoop Writable data type should implement the org.apache.hadoop.io.WritableComparable<T> interface. The WritableComparable interface extends the org.apache.hadoop.io.Writable interface and adds the compareTo() method to perform the comparisons.

In this recipe, we modify the LogWritable data type of the Implementing a custom Hadoop Writable data type recipe to implement the WritableComparable interface.

How to do it...

The following are the steps to implement a custom Hadoop WritableComparable data type for the HTTP server log entries, ...

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