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Difficulty: MediumCloudWatch Metrics and Alarms

A company is hosting a file-sharing application on an Amazon EC2 instance that runs with standard monitoring enabled. To detect sudden spikes in outbound data transfer, a SysOps Administrator creates an Amazon CloudWatch alarm for the NetworkOut metric. The alarm is configured with a threshold of 500,000,000500,000,000 bytes, a period of 11 minute, and an evaluation period of 22. During a testing window, a large file transfer causes the NetworkOut metric to exceed the threshold for exactly 33 minutes, but the alarm remains in the OK state.

Which action will resolve this issue and ensure the alarm triggers during future traffic spikes?

  1. Activate detailed monitoring on the EC2 instance.Answer
  2. B
    Adjust the CloudWatch alarm period to 55 minutes.
  3. C
    Create an Amazon EventBridge rule that triggers an AWS Systems Manager Automation document to query the network metrics of the instance every 6060 seconds.
  4. D
    Reduce the Auto Scaling group cooldown period to 6060 seconds to increase the frequency of metric reporting.

Answer

Activate detailed monitoring on the EC2 instance.
The correct action is to activate detailed monitoring on the EC2 instance. Standard monitoring only publishes metrics to CloudWatch every 5 minutes. Because the alarm is configured with a 1-minute period and requires 2 consecutive breaching periods, it cannot trigger without detailed monitoring, which increases the reporting frequency to 1-minute intervals.

Step-by-Step Solution

1
Analyze the reporting frequency under standard monitoring.
Standard monitoring for Amazon EC2 publishes metrics to CloudWatch at 5-minute intervals.
Understanding the default reporting frequency is necessary to identify why the alarm failed to evaluate consecutive 1-minute periods.
2
Evaluate the alarm configuration constraints.
The alarm has a 1-minute period and requires 2 consecutive breaching periods (2 minutes of data) to trigger.
This shows that the alarm needs metric data at 1-minute intervals to evaluate consecutive periods successfully.
3
Determine the solution to align reporting frequency with the alarm period.
Enabling detailed monitoring on the EC2 instance increases the metric reporting frequency to 1-minute intervals.
This allows CloudWatch to receive data every minute, enabling the alarm to evaluate consecutive 1-minute periods and trigger during a 3-minute spike.

Key Concept

CloudWatch Detailed Monitoring vs. Standard Monitoring for EC2 instances
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Topics

CloudWatch Metrics and Alarms

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