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AWS CloudWatch is the central observability service for collecting metrics, logs, and events from your AWS resources and applications. In this guide, you’ll learn how to set up a CPU utilization alarm for an EC2 instance, ensuring you receive notifications whenever usage crosses a critical threshold.
The image shows a CPU utilization graph with a red alarm threshold line at 75%, indicating that the CPU usage has exceeded this threshold multiple times, triggering an alarm.

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Why Use CloudWatch?

With CloudWatch, you can:
  • Collect and visualize metrics (CPU, memory, disk I/O, network) from AWS services and custom applications
  • Aggregate, search, and analyze logs in real time
  • Trigger automated actions or notifications when specified events or thresholds are met
  • Build dashboards for a consolidated, at-a-glance view of your infrastructure health
Be aware that custom metrics and detailed monitoring (1-minute resolution) may incur additional charges.

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Key CloudWatch Components

ComponentPurpose
MetricsTime-series data for resource performance (e.g., CPUUtilization).
LogsCentralized aggregation and querying of application and system logs.
AlarmsThreshold-based triggers to send notifications or invoke actions.
DashboardsCustomizable visualizations combining metrics and logs in one view.
Events/RulesAutomated reactions to state changes or scheduled tasks across AWS.
The image explains AWS Cloudwatch, highlighting its use for monitoring and observability, setting up alarms for issues, and analyzing data through dashboards.

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Demo: Configure a High-CPU Alarm

Follow these steps in the AWS Management Console to create an alarm that notifies you when CPU utilization exceeds 75% for 5 minutes:
  1. Navigate to CloudWatch in the AWS Console.
  2. In the sidebar, choose Alarms → All alarms → Create alarm.
  3. Under Select metric, pick the EC2 namespace and then Per-Instance Metrics → CPUUtilization.
  4. Click Select metric for your target instance.
  5. On the Specify metric and conditions page:
    • Threshold type: Static
    • Whenever CPUUtilization is: > 75
    • For: 5 consecutive periods of 1 minute each
  6. Under Configure actions, choose an SNS topic or create a new one to send email notifications.
  7. (Optional) Add tags to organize billing and access management.
  8. Review settings and click Create alarm.
Once activated, CloudWatch will continuously evaluate the metric and send an email via SNS whenever CPU usage remains above 75% for 5 minutes.
Ensure your SNS subscription is confirmed; otherwise, you won’t receive alarm notifications.

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Further Reading & References

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