Posted On: Feb 24, 2022

Amazon EC2 Auto Scaling Warm Pools now support two new features: you can now hibernate your Warm Pool instances and you can configure your Auto Scaling group to return running instances to a Warm Pool on scale-in. With Warm Pools, you can scale out faster by bringing instances into service from a pre-initialized pool of EC2 instances. Warm Pools are a good fit for applications that have time consuming initialization steps — like loading gigabytes of data, provisioning services, or running custom scripts — that can take several minutes or longer before those EC2 instances are ready to serve traffic.

  • Hibernate Support for Warm Pools helps applications with significant memory state scale-out faster. You can now choose to put your Warm Pool instances in the Hibernated state, in addition to the previously supported states of Stopped and Running. Choosing hibernation allows you to pre-initialize the entire EC2 instance state, not just the disk state, for instances that need to rebuild significant memory state before being placed in service.
  • Scale-in to Warm Pool saves you from having to rebuild a new Warm Pool instance during scale-in. This enhancement allows running instances to be placed back into the Warm Pool during a scale-in event. Previously, EC2 Auto Scaling would terminate one of the running “in-service” instances during scale-in and then launch and pre-initialize a new instance to replenish the Warm Pool. Now, instances can be placed back into the Warm Pool in the desired state - stopped, hibernated, or running, but idle.

These features are available through the AWS SDKs, AWS Command Line Interface (CLI), and AWS CloudFormation. AWS Management Console support for creating hibernated Warm Pool instances and for scale-in to Warm Pools is coming soon. To learn more about this feature, visit the Warm Pool documentation. Hibernation supports most, but not all, instance types and operating systems. Please refer to the hibernation documentation for supported configurations. Scale-in to Warm Pools is available in all public AWS Regions. See our documentation on Hibernate support for Warm Pools for a list of the regions where this feature is supported.