Often we require multiple MapReduce applications to be executed in a workflow-like manner to achieve our objective. Hadoop ControlledJob and JobControl classes provide a mechanism to execute a simple workflow graph of MapReduce jobs by specifying the dependencies between them.

In this recipe, we execute the log-grep MapReduce computation followed by the log-analysis MapReduce computation on an HTTP server log dataset. The log-grep computation filters the input data based on a regular expression. The log-analysis computation analyses the filtered data. Hence, the log-analysis computation is dependent on the log-grep computation. We use the ControlledJob class to express this dependency and use the JobControl class to execute both the related MapReduce computations.