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Difficulty: EasyImplementing Auto Scaling and Fault Tolerance

A data processing workload is hosted on a fleet of Amazon EC2 instances managed by an Auto Scaling group. The launch template uses a user data bootstrap script to pull dependencies and configure the application, taking 77 minutes before the instance is ready to accept tasks. The Auto Scaling group scales out using a step scaling policy with a cooldown set to 300300 seconds. During traffic bursts, the Auto Scaling group launches multiple waves of redundant instances before the initial new instances can begin processing tasks, resulting in resource over-provisioning. Which configuration change will prevent this redundant instance creation?

  1. Increase the Auto Scaling group's default cooldown and instance warm-up periods to at least 420420 seconds.Answer
  2. B
    Decrease the Auto Scaling group's default cooldown period to 180180 seconds to force more frequent policy evaluations.
  3. C
    Request an Application Load Balancer pre-warming from AWS Support to absorb the incoming burst traffic.
  4. D
    Consolidate all egress traffic through a single NAT Gateway to speed up the download of bootstrap files.

Answer

Increase the Auto Scaling group's default cooldown and instance warm-up periods to at least 420420 seconds.
The correct answer is to increase the Auto Scaling group's default cooldown and instance warm-up periods to at least 420420 seconds. This aligns the scaling policy evaluation timing with the actual duration needed for a new instance to become healthy, preventing premature launch of extra instances.

Step-by-Step Solution

1
Analyze the bootstrapping duration of the instances.
The instance takes 77 minutes to initialize, which is equal to 420420 seconds.
We must determine the minimum time needed for a new instance to become healthy and start handling traffic.
2
Compare the initialization time with the current scaling policy cooldown configuration.
The current cooldown is 300300 seconds, which is shorter than the 420420 seconds required for bootstrapping.
This mismatch causes the Auto Scaling group to trigger subsequent scaling actions before the first instance starts taking load.
3
Adjust the scaling parameters to prevent premature scale-out.
Increasing the cooldown and warm-up periods to at least 420420 seconds allows the scaling group to pause further scaling actions until the new instance is active.
This aligns the scaling feedback loop with actual instance availability, stopping the redundant creation of instances.

Key Concept

Auto Scaling Cooldown and Warm-up Alignment
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Topics

Implementing Auto Scaling and Fault Tolerance