Starting today customers can view graphs of 23 job flow metrics within the EMR Console by selecting the Monitoring tab in the Job Flow Details page. These metrics are pushed CloudWatch every five minutes at no cost to you and include information on: Job flow progress including metrics on the number of map and reduce tasks running and remaining in your job flow and the number of bytes read and written to S3 and HDFS. Job flow contention including metrics on HDFS utilization, map and reduce slots open, jobs running, and the ratio between map tasks remaining and map slots. Job flow health including metrics on whether your job flow is idle, if there are missing data blocks, and if there are any dead nodes.
via NoSQL databases