Getting Started with Amazon CloudWatch: Essential Commands for Monitoring

Amazon CloudWatch is a powerful observability service that enables you to monitor AWS resources, applications, and services in real-time. Whether you’re managing a simple web app or a multi-region distributed system, CloudWatch helps you collect, analyze, and act on performance data to ensure your systems run smoothly. In this post, we’ll cover some essential commands to get started with CloudWatch using the AWS Command Line Interface (CLI).

What is Amazon CloudWatch?

Amazon CloudWatch provides monitoring and observability capabilities for AWS resources, custom metrics, logs, and application insights. It offers features such as alarms, dashboards, log analysis, and anomaly detection, enabling you to keep your infrastructure and applications running efficiently.

Setting Up AWS CLI for CloudWatch

To use CloudWatch with the AWS CLI, follow these steps:

1. Install the AWS CLI:
   Download and install the AWS CLI from the official AWS CLI page.

2. Configure AWS CLI:
   Run the following command to configure your AWS CLI with access credentials, region, and output format:

   aws configure
   

   Provide your AWS Access Key, Secret Access Key, default region, and output format (e.g., json or text).

3. Verify Setup:
   Test your configuration with a simple command:

   aws sts get-caller-identity
   

Essential CloudWatch Commands

View Metrics for AWS Services

List available metrics:

aws cloudwatch list-metrics

Filter metrics by namespace (e.g., EC2):

aws cloudwatch list-metrics --namespace "AWS/EC2"

Retrieve metrics for a specific resource:

aws cloudwatch get-metric-data --metric-data-queries file://metric_query.json --start-time <START_TIME> --end-time <END_TIME>

Replace <START_TIME> and <END_TIME> with the desired time range.

Create and Manage Alarms

Create a CPU utilization alarm for an EC2 instance:

aws cloudwatch put-metric-alarm \
    --alarm-name "HighCPUUtilization" \
    --metric-name "CPUUtilization" \
    --namespace "AWS/EC2" \
    --statistic "Average" \
    --period 300 \
    --threshold 80 \
    --comparison-operator "GreaterThanThreshold" \
    --dimensions Name=InstanceId,Value=<INSTANCE_ID> \
    --evaluation-periods 2 \
    --alarm-actions <ARN_OF_ACTION>

Replace <INSTANCE_ID> with your EC2 instance ID and <ARN_OF_ACTION> with the ARN of the action (e.g., SNS topic).

View existing alarms:

aws cloudwatch describe-alarms

Delete an alarm:

aws cloudwatch delete-alarms --alarm-names "HighCPUUtilization"

Monitor Logs

List all log groups:

aws logs describe-log-groups

View log streams for a specific log group:

aws logs describe-log-streams --log-group-name <LOG_GROUP_NAME>

Fetch log events from a stream:

aws logs get-log-events --log-group-name <LOG_GROUP_NAME> --log-stream-name <LOG_STREAM_NAME>

Replace <LOG_GROUP_NAME> and <LOG_STREAM_NAME> with the appropriate names.

Insights for Logs

Run a CloudWatch Logs Insights query:

aws logs start-query \
    --log-group-names <LOG_GROUP_NAME> \
    --start-time <START_TIME> \
    --end-time <END_TIME> \
    --query-string "<QUERY_STRING>"

Example query for error messages:

aws logs start-query \
    --log-group-names "MyAppLogs" \
    --start-time 1672444800 \
    --end-time 1672531200 \
    --query-string "fields @timestamp, @message | filter @message like /error/"

Create Dashboards

Create a custom dashboard:

aws cloudwatch put-dashboard \
    --dashboard-name "MyDashboard" \
    --dashboard-body file://dashboard.json

Replace dashboard.json with a JSON file containing the dashboard configuration.

List existing dashboards:

aws cloudwatch list-dashboards

Delete a dashboard:

aws cloudwatch delete-dashboards --dashboard-names "MyDashboard"

Custom Metrics

Publish a custom metric:

aws cloudwatch put-metric-data \
    --namespace "MyAppMetrics" \
    --metric-name "RequestLatency" \
    --dimensions InstanceId=<INSTANCE_ID> \
    --value 100 \
    --unit Milliseconds

Retrieve data for your custom metric:

aws cloudwatch get-metric-data --metric-data-queries file://metric_query.json --start-time <START_TIME> --end-time <END_TIME>

Anomaly Detection

Create an anomaly detection model:

aws cloudwatch put-anomaly-detector \
    --namespace "AWS/EC2" \
    --metric-name "CPUUtilization" \
    --dimensions Name=InstanceId,Value=<INSTANCE_ID>

List anomaly detection models:

aws cloudwatch describe-anomaly-detectors

Delete an anomaly detection model:

aws cloudwatch delete-anomaly-detector \
    --namespace "AWS/EC2" \
    --metric-name "CPUUtilization" \
    --dimensions Name=InstanceId,Value=<INSTANCE_ID>

Automating with Scripts

You can automate CloudWatch monitoring tasks with shell scripts. Below is an example of a script to check for active alarms every 5 minutes and send notifications if any are detected.

#!/bin/bash

while true; do
    alarms=$(aws cloudwatch describe-alarms --state-value ALARM)
    if [[ ! -z "$alarms" ]]; then
        echo "Active alarms detected:"
        echo "$alarms"
        # Add your notification logic here
    else
        echo "No active alarms."
    fi
    sleep 300
done

Amazon CloudWatch provides a versatile set of features to monitor your AWS resources and applications effectively. By mastering the essential CLI commands covered here, you can simplify monitoring, automate routine tasks, and respond proactively to performance issues.

For more advanced scenarios, refer to the official Amazon CloudWatch Documentation.