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 others for your particular environment, as each has its own pros and cons.