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Difficulty: MediumAuto Scaling and Elasticity

A SysOps administrator is managing an Amazon EC2 Auto Scaling group (ASG) that hosts a batch processing application. To accommodate a predictable surge in workload, the administrator configured a scheduled scaling action to increase the desired capacity of the ASG from 22 to 1010 instances daily at 06:00 UTC. However, the administrator notices that the desired capacity remains at 22 at 06:00 UTC, and no scaling occurs. The administrator verifies that dynamic scaling policies triggered by CloudWatch alarms are still scaling the group successfully. What is the most likely cause of this issue?

  1. The ScheduledActions scaling process of the Auto Scaling group has been suspended.Answer
  2. B
    The cooldown period of the Auto Scaling group is currently active, preventing any changes to the desired capacity.
  3. C
    The CloudWatch alarm associated with the scheduled scaling action has been disabled or deleted.
  4. D
    The Auto Scaling group's service-linked role lacks the iam:PassRole permission to execute scheduled tasks.

Answer

The ScheduledActions scaling process of the Auto Scaling group has been suspended.
The correct answer is that the ScheduledActions scaling process of the Auto Scaling group has been suspended. Amazon EC2 Auto Scaling allows you to suspend and resume individual scaling processes. If ScheduledActions is suspended, the Auto Scaling group will not execute any scheduled scaling actions. However, since processes like Launch and AlarmNotification are still active, dynamic scaling policies triggered by CloudWatch alarms will continue to work.

Step-by-Step Solution

1
Identify the symptoms of the scaling failure.
Scheduled scaling actions are not executing, but dynamic scaling via CloudWatch alarms is functioning properly.
This indicates that resource launching, terminating, and alarm notification processes are active, pointing to a process-specific suspension.
2
Analyze the impact of Auto Scaling suspended processes.
Suspending the ScheduledActions process specifically halts scheduled scaling actions without impacting other activities.
Auto Scaling allows administrators to suspend and resume individual processes to troubleshoot or manage the group.
3
Eliminate other potential causes.
Cooldown periods do not affect scheduled scaling. Scheduled actions do not use CloudWatch alarms. Service-linked roles have built-in permissions.
These alternate explanations are inconsistent with AWS Auto Scaling architecture and functionality.

Key Concept

Auto Scaling Suspended Processes
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Topics

Auto Scaling and Elasticity

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