Amazon CloudWatch — Monitoring & Alarms | NextGen Playground Academy

What is CloudWatch?

Amazon CloudWatch is AWS's monitoring and observability service. It collects metrics, logs, and events from AWS resources and applications.

CloudWatch Components

Component	Purpose
Metrics	Numerical data points over time
Alarms	Trigger actions based on thresholds
Logs	Centralized log collection
Dashboards	Visual monitoring displays
Events	React to state changes

EC2 Default Metrics

CloudWatch automatically collects these EC2 metrics (5-minute intervals):

Metric	Description
CPUUtilization	CPU usage percentage
NetworkIn/Out	Network bytes transferred
DiskReadOps/WriteOps	Disk I/O operations
StatusCheckFailed	Instance health checks

Enabling Detailed Monitoring

# Enable 1-minute metrics (additional cost)
aws ec2 monitor-instances --instance-ids i-0123456789abcdef0
 
# Verify
aws cloudwatch list-metrics \
  --namespace AWS/EC2 \
  --dimensions Name=InstanceId,Value=i-0123456789abcdef0

CloudWatch Alarms

Creating a CPU Alarm

aws cloudwatch put-metric-alarm \
  --alarm-name "HighCPU-nextgen-web" \
  --alarm-description "CPU above 80% for 5 minutes" \
  --metric-name CPUUtilization \
  --namespace AWS/EC2 \
  --statistic Average \
  --period 300 \
  --threshold 80 \
  --comparison-operator GreaterThanThreshold \
  --evaluation-periods 2 \
  --dimensions Name=InstanceId,Value=i-0123456789abcdef0 \
  --alarm-actions arn:aws:sns:us-east-1:123456789012:alerts

Common Alarm Configurations

# Disk space alarm (requires CloudWatch Agent)
aws cloudwatch put-metric-alarm \
  --alarm-name "LowDisk-nextgen-web" \
  --metric-name disk_used_percent \
  --namespace CWAgent \
  --statistic Average \
  --period 300 \
  --threshold 85 \
  --comparison-operator GreaterThanThreshold \
  --evaluation-periods 2 \
  --dimensions Name=InstanceId,Value=i-0123456789abcdef0
 
# Status check alarm (auto-recover)
aws cloudwatch put-metric-alarm \
  --alarm-name "StatusCheck-nextgen-web" \
  --metric-name StatusCheckFailed \
  --namespace AWS/EC2 \
  --statistic Maximum \
  --period 60 \
  --threshold 1 \
  --comparison-operator GreaterThanOrEqualToThreshold \
  --evaluation-periods 3 \
  --dimensions Name=InstanceId,Value=i-0123456789abcdef0 \
  --alarm-actions arn:aws:automate:us-east-1:ec2:recover

CloudWatch Agent

The CloudWatch Agent collects system-level metrics (memory, disk) and custom application logs.

Installation

# Download and install
sudo yum install -y amazon-cloudwatch-agent
 
# Or download directly
wget https://s3.amazonaws.com/amazoncloudwatch-agent/amazon_linux/amd64/latest/amazon-cloudwatch-agent.rpm
sudo rpm -U ./amazon-cloudwatch-agent.rpm

Configuration

{
  "metrics": {
    "namespace": "CWAgent",
    "metrics_collected": {
      "mem": {
        "measurement": ["mem_used_percent"],
        "metrics_collection_interval": 60
      },
      "disk": {
        "measurement": ["disk_used_percent"],
        "metrics_collection_interval": 60,
        "resources": ["/", "/data"]
      }
    }
  },
  "logs": {
    "logs_collected": {
      "files": {
        "collect_list": [
          {
            "file_path": "/var/log/messages",
            "log_group_name": "nextgen-system-logs",
            "log_stream_name": "{instance_id}"
          },
          {
            "file_path": "/var/log/nginx/access.log",
            "log_group_name": "nextgen-nginx-access",
            "log_stream_name": "{instance_id}"
          }
        ]
      }
    }
  }
}

# Start the agent
sudo /opt/aws/amazon-cloudwatch-agent/bin/amazon-cloudwatch-agent-ctl \
  -a fetch-config \
  -m ec2 \
  -c file:/opt/aws/amazon-cloudwatch-agent/etc/config.json \
  -s

CloudWatch Logs

Querying Logs with Insights

-- Find errors in the last hour
fields @timestamp, @message
| filter @message like /ERROR/
| sort @timestamp desc
| limit 50
 
-- Count requests by status code
fields @timestamp, status
| stats count(*) by status
| sort count desc
 
-- Average response time
fields @timestamp, response_time
| stats avg(response_time) as avg_time, max(response_time) as max_time by bin(5m)

CloudWatch Dashboards

aws cloudwatch put-dashboard \
  --dashboard-name "NextGen-Overview" \
  --dashboard-body '{
    "widgets": [
      {
        "type": "metric",
        "properties": {
          "metrics": [
            ["AWS/EC2", "CPUUtilization", "InstanceId", "i-0123456789abcdef0"]
          ],
          "period": 300,
          "stat": "Average",
          "title": "CPU Utilization"
        }
      }
    ]
  }'

# Create an SNS topic for alerts
aws sns create-topic --name nextgen-alerts
 
# Subscribe email
aws sns subscribe \
  --topic-arn arn:aws:sns:us-east-1:123456789012:nextgen-alerts \
  --protocol email \
  --notification-endpoint team@nextgenplayground.org
 
# Use topic ARN in alarm actions

Summary

You've learned:

CloudWatch metrics, alarms, and dashboards
Monitoring EC2 with default and custom metrics
Installing and configuring the CloudWatch Agent
Centralized logging with CloudWatch Logs
SNS notifications for alert delivery

Next Steps

You now have a solid AWS compute foundation. Combine these skills with your Terraform knowledge to provision and monitor infrastructure as code.

Amazon CloudWatch — Monitoring & Alarms

Learning Objectives