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Chapter 6. Metapatterns

This chapter is different from the others in that it doesn’t contain patterns for solving a particular problem, but patterns that deal with patterns. The term metapatterns is directly translated to “patterns about patterns.” The first method that will be discussed is job chaining, which is piecing together several patterns to solve complex, multistage problems. The second method is job merging, which is an optimization for performing several analytics in the same MapReduce job, effectively killing multiple birds with one stone.

Job Chaining

Job chaining is extremely important to understand and have an operational plan for in your environment. Many people find that they can’t solve a problem with a single MapReduce job. Some jobs in a chain will run in parallel, some will have their output fed into other jobs, and so on. Once you start to understand how to start solving problems as a series of MapReduce jobs, you’ll be able to tackle a whole new class of challenges.

Job chaining is one of the more complicated processes to handle because it’s not a feature out of the box in most MapReduce frameworks. Systems like Hadoop are designed for handling one MapReduce job very well, but handling a multistage job takes a lot of manual coding. There are operational considerations for handling failures in the stages of the job and cleaning up intermediate output. In this section, a few different approaches to job chaining will be discussed. Some will seem more appealing than ...

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