This topic describes the auto scaling feature of E-MapReduce (EMR). You can configure auto scaling rules based on your business requirements and policies. Auto scaling applies only to Hadoop clusters of EMR. After this feature is enabled and configured, EMR automatically adds task nodes to ensure sufficient computing capabilities when your business loads increase and removes task nodes to reduce costs when your business loads decrease.


You can enable auto scaling in the following scenarios to reduce costs and improve task execution efficiency:
  • Add task nodes at the scheduled time to temporarily supplement the computing capabilities.
  • Add task nodes based on the settings of certain cluster metrics to ensure that important jobs are completed on time.


Auto scaling allows you to purchase preemptible or pay-as-you-go instances as required.