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Monitoring AWS EC2 Instances with Amazon CloudWatch

Monitoring is an essential part of managing cloud infrastructure. Running an Amazon EC2 instance is only the first step; administrators also need visibility into CPU usage, network activity, disk utilization, application logs, and system health. Amazon CloudWatch provides monitoring, metrics, logs, dashboards, and alarms that help identify infrastructure issues and respond to them proactively.

Deepak Bairwa

I am a Cloud Engineer Intern.

What is Amazon CloudWatch?

Amazon CloudWatch is an AWS monitoring and observability service that provides visibility into AWS resources and applications.
It can be used for:
  • Monitoring infrastructure metrics
  • Collecting application and system logs
  • Creating alarms
  • Building dashboards
  • Detecting performance issues
  • Automating responses to certain conditions
Many AWS services automatically publish metrics to CloudWatch.

EC2 Monitoring

Amazon EC2 provides several useful metrics through CloudWatch.
Common metrics include:
  • CPU utilization
  • Network traffic
  • Disk-related metrics
  • Status checks
  • Instance health
For example, if CPU utilization remains consistently high, it could indicate that the workload needs additional compute capacity or further investigation.
AWS provides basic EC2 monitoring by default, while detailed monitoring can provide metrics at one-minute intervals.

Basic Monitoring Architecture

A simple monitoring setup can look like:
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Amazon EC2
|
+---------+---------+
| |
Metrics Logs
| |
v v
CloudWatch CloudWatch
Metrics Logs
| |
+---------+---------+
|
v
CloudWatch
Alarm
|
v
SNS
|
v
Notification
This allows administrators to monitor infrastructure and receive alerts when predefined conditions occur.

Creating a CPU Alarm

One common example is creating an alarm when CPU utilization remains above a defined threshold.
For example:
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Metric: CPUUtilization
Threshold: 80%
Period: 5 minutes
Action: Send notification
If the metric remains above the configured threshold for the required evaluation periods, the alarm can enter the ALARM state and trigger an action such as sending a notification through Amazon SNS.
The threshold should be based on the workload. High CPU does not always indicate a problem because some applications are designed to use available CPU resources efficiently.

Monitoring Memory and Disk Usage

One important consideration is that standard EC2 metrics do not provide every operating-system-level metric.
For example, administrators may want to monitor:
  • RAM utilization
  • Disk utilization
  • Swap usage
  • Process-level metrics
  • Application logs
The CloudWatch agent can be installed on EC2 instances to collect additional system-level metrics and logs. AWS specifically recommends using the CloudWatch agent to ingest log files from EC2 instances.
A monitoring flow can therefore become:
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EC2 Instance
|
v
CloudWatch Agent
|
+---- CPU / Memory
|
+---- Disk Usage
|
+---- Application Logs
|
v
CloudWatch

Monitoring Application Logs

Infrastructure metrics alone may not be enough to troubleshoot an application.
For example, an EC2 server could show normal CPU utilization while the application is returning errors.
Application logs can provide information such as:
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Application Error
Database Connection Failed
HTTP 500
Authentication Failed
Service Unavailable
CloudWatch Logs can be used to collect and search these logs.
This gives administrators a better view of both the infrastructure layer and application layer.

Creating a CloudWatch Dashboard

A CloudWatch dashboard can provide a centralized view of important resources.
For example:
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+--------------------------------------+
| EC2 Monitoring Dashboard |
+--------------------------------------+
| CPU Utilization | Network Traffic |
+--------------------------------------+
| Memory Usage | Disk Usage |
+--------------------------------------+
| Status Checks | Application Logs |
+--------------------------------------+
Dashboards are particularly useful when managing multiple servers because administrators can quickly identify abnormal behavior instead of checking individual instances manually.
CloudWatch dashboards can provide a unified view of metrics and logs across workloads.

Using SNS for Notifications

CloudWatch alarms can be integrated with Amazon SNS to send notifications.
For example:
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CPU > 80%
|
v
CloudWatch Alarm
|
v
Amazon SNS
|
v
Administrator Notification
This allows teams to respond to infrastructure problems before they become major incidents.

Monitoring EC2 Health

EC2 also provides status checks that help identify problems affecting an instance or the underlying AWS infrastructure.
When a status check fails, administrators can investigate whether the issue is related to the instance, operating system, networking, or underlying infrastructure.
AWS also supports EventBridge for responding to AWS service events and automating actions.

Practical Monitoring Strategy

A useful EC2 monitoring strategy can be divided into three levels:

Level 1 — Infrastructure

Monitor:
  • CPU
  • Network
  • Instance status
  • Storage

Level 2 — Operating System

Monitor:
  • Memory
  • Disk utilization
  • Processes
  • System logs

Level 3 — Application

Monitor:
  • Application errors
  • Response time
  • HTTP status codes
  • Database connectivity
  • Service availability
This layered approach makes troubleshooting more effective.

Example Troubleshooting Workflow

Suppose users report that an application is slow.
The administrator can investigate:
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User Complaint
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v
Check EC2 Status
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v
Check CPU / Network
|
v
Check Memory / Disk
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v
Review Application Logs
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v
Identify Root Cause
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v
Take Corrective Action
This approach avoids immediately changing infrastructure without first identifying the actual problem.

Cost Considerations

Monitoring should also be designed with cost in mind.
Detailed monitoring, custom metrics, log ingestion, log storage, and alarms can introduce additional CloudWatch charges. AWS recommends evaluating which metrics and logs are actually required and applying more detailed monitoring where it provides meaningful value.
For example:
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Production → Detailed monitoring + important logs
Development → Basic monitoring + essential logs
This can provide useful visibility while controlling unnecessary monitoring costs.

Best Practices

When implementing CloudWatch monitoring:
  • Define important metrics before creating alarms.
  • Monitor both infrastructure and application health.
  • Use the CloudWatch agent for additional OS-level metrics.
  • Create alarms for meaningful conditions.
  • Avoid excessive alerts that create notification fatigue.
  • Use dashboards for critical workloads.
  • Retain logs according to business requirements.
  • Review monitoring costs periodically.
  • Test notification and alarm workflows.
  • Document the response procedure for critical alarms.

Conclusion

Effective monitoring is a critical part of running reliable AWS workloads. Amazon CloudWatch provides the foundation for collecting metrics, logs, dashboards, and alarms across AWS resources.
For EC2 environments, combining standard CloudWatch metrics with the CloudWatch agent, alarms, dashboards, and notifications provides much better visibility into infrastructure and application health.
The goal of monitoring should not simply be to collect as much data as possible. Instead, it should provide the right information at the right time so that administrators can detect issues, troubleshoot efficiently, and take corrective action before they impact users.
# amazon-cloudwatch# aws-cloudwatch# monitoring# monitoring-observability
Any opinions in this article are those of the individual author and may not reflect the opinions of AWS.
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