A cluster hosted by Amazon EMR runs in a complex ecosystem made up of several types of open-source software, custom application code, and Amazon Web Services. An issue in any of these parts can cause the cluster to fail or take longer than expected to complete. The following topics will help you figure out what has gone wrong in your cluster and give you suggestions on how to fix it.
When you are developing a new Hadoop application, we recommend that you enable debugging and process a small but representative subset of your data to test the application. You may also want to run the application step-by-step to test each step separately. For more information, see Configure Logging and Debugging (Optional) and Step 5: Test the Cluster Step by Step.