3.2.1.9. Collecting Custom Metrics (CloudWatch Agent)

First Principle: Collecting custom metrics provides precise insights into system performance and behavior, enabling more effective alerting and troubleshooting.

While standard AWS service metrics provide foundational insights, they often lack the granularity needed for deep application-specific or operating system-level observability. This adheres to the principle of comprehensive monitoring.

The CloudWatch Agent is the primary tool for this purpose. It allows you to collect a wide array of custom metrics from:

• Operating Systems: Such as memory utilization, disk space, swap usage, and process counts from EC2 instances or on-premises servers.
• Applications: Including custom application counters (e.g., number of successful API calls, failed logins), business metrics (e.g., items added to cart, user sign-ups), and log events.

Key Capabilities of CloudWatch Agent:

• OS Metrics: CPU, memory, disk, network (beyond default EC2 metrics).
• Application Metrics: Custom KPIs, business metrics.
• Log Collection: Send logs to CloudWatch Logs.
• Flexible Configuration: Define what to collect and how often.

Scenario: A DevOps team is running a custom application on EC2 instances. They need to monitor application-specific metrics like "number of successful transactions per minute" and system-level metrics like "memory utilization" which are not available by default in Amazon CloudWatch.

Reflection Question: How would you install and configure the CloudWatch Agent on these EC2 instances to collect both custom application metrics and detailed operating system metrics, providing more precise insights for effective alerting and troubleshooting?

These custom metrics enhance observability by providing tailored operational insights. For instance, you can monitor application-specific KPIs, track custom events, and create highly relevant dashboards that reflect your unique business logic and performance indicators. The agent's flexible configuration allows you to define exactly what data to collect and how often.

💡 Tip: Consider what application-specific metrics (e.g., transaction latency, queue depth, specific error codes) would be most valuable for your applications to monitor beyond basic CPU or network usage.