Amazon EMR
Management Guide

Create a Cluster with Instance Fleets or Uniform Instance Groups

When you create a cluster and specify the configuration of the master node, core nodes, and task nodes, you have two configuration options. You can use instance fleets or uniform instance groups. The configuration option you choose applies to all nodes, it applies for the lifetime of the cluster, and instance fleets and instance groups cannot coexist in a cluster. The instance fleets configuration is available in Amazon EMR version 4.8.0 and later, excluding 5.0.x versions.

You can use the EMR console, the AWS CLI, or the EMR API to create clusters with either configuration. When you use the create-cluster command from the AWS CLI, you use either the --instance-fleets parameters to create the cluster using instance fleets or, alternatively, you use the --instance-groups parameters to create it using uniform instance groups.

The same is true using the EMR API. You use either the InstanceGroups configuration to specify an array of InstanceGroupConfig objects, or you use the InstanceFleets configuration to specify an array of InstanceFleetConfig objects.

In the EMR console, if you use the default Quick Options settings when you create a cluster, Amazon EMR applies the uniform instance groups configuration to the cluster and uses On-Demand Instances. To use Spot Instances with uniform instance groups, or to configure instance fleets and other customizations, choose Advanced Options.


To quickly and easily replicate a cluster you have already created, Amazon EMR gives you two options in the console. You can clone the cluster or generate a create cluster CLI command. First, choose Cluster list and then choose the cluster you want to replicate. Choose AWS CLI export to have Amazon EMR generate the equivalent create cluster CLI command for the cluster, which you can then copy and paste. Choose the Clone button to have Amazon EMR replicate your console setup. Amazon EMR presents you with the last step of the Advanced Options to confirm the cluster's configuration. You can either choose Create cluster to create the new cluster (with the same name and a different cluster ID), or you can choose Previous to go back and change settings.

Instance Fleets

The instance fleets configuration offers the widest variety of provisioning options for EC2 instances. Each node type has a single instance fleet, and the task instance fleet is optional. For each instance fleet, you specify up to five instance types, which can be provisioned as On-Demand and Spot Instances. For the core and task instance fleets, you assign a target capacity for On-Demand Instances, and another for Spot Instances. Amazon EMR chooses any mix of the five instance types to fulfill the target capacities, provisioning both On-Demand and Spot Instances. For the master node type, Amazon EMR chooses a single instance type from your list of up to five, and you specify whether it's provisioned as an On-Demand or Spot Instance. Instance fleets also provide additional options for Spot Instance purchases, which include a defined duration (also known as a spot block) and a timeout that specifies an action to take if Spot capacity can't be provisioned. For more information, see Configure Instance Fleets.

Uniform Instance Groups

Uniform instance groups offer a simplified setup. Each Amazon EMR cluster can include up to 50 instance groups: one master instance group that contains one EC2 instance, a core instance group that contains one or more EC2 instances, and up to 48 optional task instance groups. Each core and task instance group can contain any number of EC2 instances. You can scale each instance group by adding and removing EC2 instances manually, or you can set up automatic scaling. For more information about configuring uniform instance groups, see Configure Uniform Instance Groups. For information about adding and removing instances, see Scaling Cluster Resources.