Termination Policy & Life Cycle Hooks
Links: 101 AWS SAA Index
Termination policy decides which instance will be deleted in case of a scale in.
Default termination policy steps:
- Find the AZ with the most number of instances.
- Find instances that are not protected from scale in.
- If there are multiple instances delete the one with the oldest launch template or configuration.
- If still there are multiple instances delete the one closest to the next billing hour.
- If still there are multiple instances then delete one at random.
Life cycle hooks¶
We have one hook at the time of launching and other at the time of termination.
One use case of launch hook would be to do some installations and checks before the machine is provisioned. Here installations and checks are the important terms.
- One use case of termination hook would be storing the logs or uploading it somewhere.
- By default as soon as an instance is launched in ASG it is InService.
The lifecycle hook puts the instance into a wait state (
Pending: Wait or
Terminating: Wait). The instance is paused until you continue or the timeout period ends.
Example use case: Use the Auto Scaling group lifecycle hook to put the instance in a wait state and launch a custom script that installs the proprietary forensic tools and performs a pre-activation status check
Last updated: 2022-05-05