4.1.1. Amazon CloudWatch for Network Metrics

Amazon CloudWatch provides a comprehensive and scalable monitoring service for collecting network metrics, enabling network specialists to track network performance, detect anomalies, and set up actionable alarms.

Scenario: You need to monitor the network performance of your EC2 instances and ALB. Specifically, you want to track network traffic in/out of EC2 instances and the latency of requests through your ALB, setting up alerts if latency exceeds a threshold.

Amazon CloudWatch is the primary monitoring and observability service for AWS. For network specialists, it's essential for understanding the performance and health of their network infrastructure.

Key Network Metrics in CloudWatch:

• EC2 Network In/Out: Bytes received/sent by EC2 instances.
• ELB (Elastic Load Balancing) Metrics: Request counts, latency, healthy host count, 5xx errors.
• NAT Gateway Metrics: Bytes processed, active connections, connection attempts.
• VPN TunnelState: Status of VPN tunnels.
• Direct Connect Metrics: Connection state, bits in/out.
• Transit Gateway Metrics: Bytes in/out, packet drops.
• Custom Metrics: Publish application-specific network metrics (e.g., latency to specific endpoints).

Key Features of CloudWatch for Network Monitoring:

• Alarms: Trigger actions (e.g., SNS notifications, Auto Scaling) based on metric thresholds.
• Dashboards: Create customizable visualizations of network metrics for real-time operational oversight.
• Logs: Collect network-related logs (e.g., VPC Flow Logs, ELB Access Logs) for detailed analysis.

Practical Implementation: Creating a CloudWatch Alarm for ALB Latency

# Assuming ALB_ARN is defined
# 1. Create a CloudWatch Alarm for ALB Latency
aws cloudwatch put-metric-alarm \
  --alarm-name "ALB-HighLatency" \
  --alarm-description "Alarm when ALB latency exceeds 0.5 seconds" \
  --metric-name "TargetResponseTime" \
  --namespace "AWS/ApplicationELB" \
  --statistic "Average" \
  --period 60 \
  --threshold 0.5 \
  --comparison-operator "GreaterThanThreshold" \
  --dimensions "Name=LoadBalancer,Value=app/my-alb/abcdef1234567890" \
  --evaluation-periods 3 \
  --alarm-actions "arn:aws:sns:us-east-1:123456789012:MyNetworkAlerts" # Replace with your SNS topic ARN

⚠️ Common Pitfall: Setting static thresholds for metrics that have dynamic behavior (e.g., CPU utilization for a spiky workload). This can lead to alert fatigue or missed issues. Use CloudWatch Anomaly Detection for dynamic thresholds.

Key Trade-Offs:

• Granularity of Metrics vs. Cost: Higher resolution metrics (e.g., 1-second data points) provide more detail but incur higher costs.

Reflection Question: How does Amazon CloudWatch, by providing comprehensive and scalable collection of network metrics (e.g., EC2 Network In/Out, ALB Latency) and actionable alarms, enable you to proactively track network performance, detect anomalies, and maintain network health?