Lab 8: SRE and Monitoring

[tivdzualubem]

Summary

This PR completes Lab 8 by extending QuickNotes with a complete SRE monitoring stack using Prometheus, Grafana, alerting, runbook documentation, and external synthetic monitoring.

Implemented

• Prometheus scraping QuickNotes every 15 seconds
• Provisioned Grafana Prometheus data source
• Provisioned four-panel Golden Signals dashboard
• Real request-latency histogram with P50 and P95 metrics
• Traffic, error-rate, and saturation panels
• High-error-rate alert for more than 5% errors sustained for five minutes
• severity: page label and linked operational runbook
• Alert validation in both Pending and Firing states
• Cloudflare Quick Tunnel through GitHub Actions
• Checkly monitoring every minute from Frankfurt and Singapore
• Same-window Prometheus and Checkly latency comparison
• Complete evidence and design answers in submissions/lab8.md

Validation

• go test ./... passed
• go vet ./... passed
• Docker Compose configuration passed validation
• Grafana dashboard JSON passed validation
• Prometheus target reported up = 1
• Alert transitioned from Pending to Firing
• Checkly recorded 100% availability during the selected 30-minute window
• The branch contains one signed Lab 8 commit and no unrelated lab submission files