Cloudwatch Monitoring

Amazon CloudWatch Monitoring

When to Use

• Setting up metrics, alarms, and dashboards for AWS services
• Building custom metrics from application logs using metric filters
• Implementing distributed tracing with AWS X-Ray
• Creating synthetic monitors with CloudWatch Synthetics
• Designing event-driven operations with CloudWatch Alarms + SNS/Lambda
• Preparing for AWS DEA-C01, DVA-C02, or DOP-C02 exams

Core Jobs

1. CloudWatch Metrics

Key concepts:

• Namespace: logical container for metrics (e.g., AWS/EC2, MyApp/Orders)
• Dimensions: key-value pairs that identify the specific metric source (InstanceId, FunctionName)
• Statistics: Average, Sum, Minimum, Maximum, SampleCount, Percentile (p99, p95)
• Period: aggregation window (60s, 300s, 3600s)
• Metrics retained: 1-second → 3 hours; 1-minute → 15 days; 5-minute → 63 days; 1-hour → 15 months

2. CloudWatch Logs

Structure:

• Log group → Log streams → log events
• Log group: named container (e.g., /aws/lambda/my-function)
• Log stream: sequence of events from a single source (e.g., one Lambda instance)
• Retention: 1 day to 10 years (default: never expire — must set retention policy)

Metric filters:

• Extract metrics from log content using filter patterns
• Pattern syntax: [ERROR], {$.statusCode = 500} (JSON), "Exception"
• Create CloudWatch metric from filter → alarm → SNS/Lambda pipeline

CloudWatch Logs Insights:

• Interactive SQL-like query language for log analysis
• Cross-log-group queries
• Key commands: fields, filter, stats, sort, limit, parse
• Pre-saved queries available for AWS service logs (Lambda, VPC Flow Logs, CloudTrail)

3. CloudWatch Alarms

Alarm states: OK → ALARM → INSUFFICIENT_DATA (not enough data points)

Actions:

• Auto Scaling: scale-out/in policies
• SNS: notify email/SMS/HTTP endpoint
• EC2: stop, terminate, reboot, recover
• Systems Manager OpsItem: create incident ticket
• Lambda: via SNS subscription

Composite alarms example (reduce noise):

ALARM("CPUHigh") AND ALARM("MemoryHigh") → PagerDuty alert
ALARM("CPUHigh") alone → Slack notification only

4. CloudWatch Logs Insights Queries

Common patterns for exam and real-world use:

# Find error count per Lambda function
fields @timestamp, @message
| filter @message like /ERROR/
| stats count() as errorCount by bin(1h)
| sort @timestamp desc

# Top 10 slowest requests
fields @timestamp, @duration
| sort @duration desc
| limit 10

# Parse custom log format
parse @message "* * * *" as requestId, statusCode, latency, path
| filter statusCode = "500"

5. AWS X-Ray Distributed Tracing

• Traces requests across microservices, Lambda functions, and AWS services
• Trace: end-to-end request lifecycle (collection of segments)
• Segment: one service's contribution to the trace (with subsegments)
• Subsegment: granular operations within a segment (DB call, external HTTP call)
• Service map: visual topology of services and their dependencies with latency/error rates

Sampling rules:

• Default: 5% of requests + 1 request/second minimum (avoid high-volume trace costs)
• Custom sampling rules: define by service name, URL path, host, HTTP method
• Reservoir = guaranteed fixed-rate; rate = percentage of remaining traffic

X-Ray SDK integration:

• Instrument AWS SDK calls automatically (DynamoDB, S3, SQS, etc.)
• Annotate with custom key-value pairs (for filtering traces)
• Add metadata for debugging (not indexed, not searchable)

X-Ray Daemon: runs as sidecar collecting segments and sending to X-Ray service (batch UDP).

6. CloudWatch Synthetics (Canaries)

• Node.js or Python scripts that simulate user interactions
• Run on schedule (e.g., every 5 minutes) or one-time
• Check: API availability, UI flows, broken links, visual regression
• Canary blueprints: API canary, heartbeat monitor, broken link checker, visual monitoring
• Results stored in S3; CloudWatch metrics generated per canary run

7. Container and Lambda Insights

Key Concepts

• CloudWatch Agent — installed on EC2/on-prem to collect OS-level metrics (memory, disk) and logs (not available by default)
• Embedded Metrics Format (EMF) — structured JSON logs with _aws metadata; CloudWatch extracts metrics automatically; no separate PutMetricData call
• Metric math — perform arithmetic on metrics (e.g., ErrorRate = Errors / Invocations × 100)
• CloudWatch Contributor Insights — analyze log data to identify top contributors (e.g., top 10 IPs causing 4xx errors)
• CloudWatch Evidently — A/B testing and feature flagging (launch features to % of users)
• CloudWatch RUM — Real User Monitoring for web applications (client-side performance)

Checklist

• CloudWatch Agent installed for OS-level metrics (memory, disk — not included by default)?
• Log group retention policy set (not "never expire")?
• Metric filters created for critical error patterns in application logs?
• Composite alarms used to reduce alert fatigue (alert only when multiple signals fire)?
• X-Ray tracing enabled for Lambda functions and API Gateway?
• Custom sampling rules defined for X-Ray (avoid tracing 100% of high-volume requests)?
• Container Insights enabled for EKS/ECS clusters?
• Synthetics canaries monitoring critical API endpoints and user flows?

Output Format

• 🔴 Critical — no alarms on critical service metrics; log groups with "never expire" retention accumulating indefinitely; X-Ray not enabled for production microservices
• 🟡 Warning — memory/disk metrics missing (CloudWatch Agent not installed); composite alarms not used (too many individual alerts); default X-Ray sampling rate too high (100% on high-volume service)
• 🟢 Suggestion — Anomaly detection alarms for variable metrics; CloudWatch Logs Insights for ad-hoc log analysis; Lambda Insights for cold start investigation

Exam Tips

• Custom metrics = 1-second resolution possible (high-resolution); standard metrics = 1-minute minimum
• Metric filters on log groups → CloudWatch metric → alarm → SNS → Lambda — classic event-driven ops pipeline; memorize this chain
• CloudWatch Logs Insights = SQL-like queries on logs; fast cross-log-group analysis without Athena
• X-Ray sampling = reduces trace volume; default 5% + 1 req/sec minimum; can configure per path/service
• Composite alarms = combine multiple alarms with AND/OR logic; reduces alert fatigue (only page when CPU AND memory high)
• Container Insights = ECS/EKS metrics (not enabled by default — must enable); Lambda Insights = Lambda performance metrics (cold starts, memory usage)
• CloudWatch Agent required for EC2 memory and disk metrics — these are NOT available without the agent
• Anomaly detection = ML baseline based on historical data; alarms fire when metric deviates beyond expected band