AWS Auto Scaling Group Scheduled Scaling Activity

Correct Answer - C.

Options A and B are incorrect because there are some scaling actions that do not need to wait for the cooldown period to expire such as a scheduled or a manual scaling action.

Option C is CORRECT because the cooldown timer does not influence the scheduled activity.

Even if the cooldown timer is running, the scheduled action takes high priority and executes immediately.

Option D is incorrect because the active cooldown timer does not override the scheduled activity.

At 8:00 AM, the scheduled scaling takes action immediately.

Reference:

https://docs.aws.amazon.com/autoscaling/ec2/userguide/schedule_time.html, https://docs.aws.amazon.com/autoscaling/ec2/userguide/Cooldown.html.

Sure, I'd be happy to help!

The scenario described in the question involves an AWS Auto Scaling group (ASG) with a scheduled scaling activity and a cooldown timer. The scheduled scaling activity is set to add more instances to the ASG at 8:00 AM every day, and the cooldown timer is set to 45 minutes. The cooldown timer is the period of time that must elapse after a scaling activity has occurred before another scaling activity can be initiated.

On a particular day, the ASG scaled up at 7:45 AM because a high CPU alarm was triggered in AWS CloudWatch. This means that the ASG added more instances before the scheduled scaling activity was set to occur. The cooldown timer for the ASG is set to 45 minutes, and it takes about 30 minutes for a new instance to finish its init scripts and serve traffic.

Given this scenario, we can consider each of the answer options in turn:

A. The scheduled scaling activity will start at 8:45 AM as the cooldown timer is reset when the scheduled activity starts and the scheduled scaling can only start until the cooldown timer expires.

This answer is not correct. While it is true that the cooldown timer is reset when a scaling activity is initiated, the scheduled scaling activity is not affected by this. The scheduled scaling activity will still occur at the specified time, regardless of whether a scaling activity has occurred earlier in the day.

B. The scheduled scaling activity will start at 8:30 AM as it needs to wait for the cooldown timer to expire.

This answer is also not correct. The cooldown timer is not related to the scheduled scaling activity. The cooldown timer applies only to scaling activities that are initiated manually or by an Amazon CloudWatch alarm. The scheduled scaling activity is initiated by a scheduled event and is not subject to the cooldown timer.

C. The scheduled scaling activity starts immediately as the scheduled action does not wait for the cooldown period to expire.

This answer is not correct either. While it is true that the scheduled scaling activity is not subject to the cooldown timer, it will not start immediately because new instances take about 30 minutes to finish their initialization scripts and serve traffic. Therefore, if the scheduled scaling activity were to start immediately, the new instances would not be ready to serve traffic until after the scheduled scaling activity was supposed to have completed.

D. The scheduled scaling will not start this time as it is overridden by the active cooldown timer. The scheduled scaling will continue to work the next day.

This answer is the correct one. When a scaling activity is initiated, the cooldown timer is triggered, and no further scaling activity can occur until the cooldown timer has expired. In this case, the ASG scaled up at 7:45 AM, triggering the cooldown timer. Since the scheduled scaling activity was set to occur at 8:00 AM, it was not able to start because the cooldown timer had not yet expired. Therefore, the scheduled scaling activity will not occur on this day, but it will continue to work normally on subsequent days.

In summary, the correct answer is D: The scheduled scaling will not start this time as it is overridden by the active cooldown timer. The scheduled scaling will continue to work the next day.