Using Spot Instances - Amazon Elastic Container Service

Using Spot Instances

A Spot Instance is an unused Amazon EC2 instance that is available for less than the On-Demand price. Because Spot Instances enable you to request unused EC2 instances at steep discounts, you can lower your Amazon EC2 costs significantly. The hourly price for a Spot Instance is called a Spot price. The Spot price of each instance type in each Availability Zone is set by Amazon EC2, and adjusted gradually based on the long-term supply of and demand for Spot Instances. For more information, see Spot Instances in the Amazon EC2 User Guide for Linux Instances.

You can register Spot Instances to your Amazon ECS clusters. For more information, see Launching an Amazon ECS Linux container instance.

Spot Instance Draining

Amazon EC2 terminates, stops, or hibernates your Spot Instance when the Spot price exceeds the maximum price for your request or capacity is no longer available. Amazon EC2 provides a Spot Instance two-minute interruption notice for terminate and stop actions. It does not provide the two-minute notice for the hibernate action. If Amazon ECS Spot Instance draining is enabled on the instance, ECS receives the Spot Instance interruption notice and places the instance in DRAINING status.


Amazon ECS does not receive a notice from Amazon EC2 when instances are removed by Auto Scaling Capacity Rebalancing. For more information, see Amazon EC2 Auto Scaling Capacity Rebalancing.

When a container instance is set to DRAINING, Amazon ECS prevents new tasks from being scheduled for placement on the container instance. Service tasks on the draining container instance that are in the PENDING state are stopped immediately. If there are container instances in the cluster that are available, replacement service tasks are started on them.

Spot Instance draining is turned off by default and must be manually enabled. To enable Spot Instance draining for a new container instance, when launching the container instance add the following script into the User data field, replacing MyCluster with the name of the cluster to register the container instance to.

#!/bin/bash cat <<'EOF' >> /etc/ecs/ecs.config ECS_CLUSTER=MyCluster ECS_ENABLE_SPOT_INSTANCE_DRAINING=true EOF

For more information, see Launching an Amazon ECS Linux container instance.

To turn on Spot Instance draining for an existing container instance
  1. Connect to the Spot Instance over SSH.

  2. Edit the /etc/ecs/ecs.config file and add the following:

  3. Restart the ecs service.

    • For the Amazon ECS-optimized Amazon Linux 2 AMI:

      sudo systemctl restart ecs
    • For the Amazon ECS-optimized Amazon Linux AMI:

      sudo stop ecs && sudo start ecs
  4. (Optional) You can verify that the agent is running and see some information about your new container instance by querying the agent introspection API operation. For more information, see Amazon ECS container agent introspection.

    curl http://localhost:51678/v1/metadata