A lifecycle hook tells Auto Scaling that you want to perform an action on an instance that is not actively in service; for example, either when the instance launches or before the instance terminates.
This step is a part of the procedure for adding a lifecycle hook to an Auto Scaling group:
(Optional) Create a Lambda function and a rule that allows CloudWatch Events to invoke your Lambda function when Auto Scaling launches or terminates instances.
(Optional) Create a notification target and an IAM role. The target can be either an Amazon SQS queue or an Amazon SNS topic. The role allows Auto Scaling to publish lifecycle notifications to the target.
Create the lifecycle hook. Specify whether the hook is used when the instances launch or terminate.
If you need more time, record the lifecycle action heartbeat to keep the instance in a pending state.
If you finish before the timeout period ends, complete the lifecycle action.
For more information, see Auto Scaling Lifecycle Hooks in the Auto Scaling User Guide.
If you exceed your maximum limit of lifecycle hooks, which by default is 50 per Auto Scaling group, the call fails. For information about updating this limit, see AWS Service Limits in the Amazon Web Services General Reference.