Add enhancement recommendation: System Logs and Observability

[Copilot]

The system already runs Prometheus but its scrape config points only at itself — none of the application services are monitored. Grafana is being added but has nothing to visualize. This document evaluates all six candidate enhancements and recommends completing the observability stack as the highest-value next step.

What's in the document (ENHANCEMENT_RECOMMENDATION.md)

• Current system inventory — table of all running services, tech, and role
• All six options evaluated — each assessed for distributed systems learning value, implementation scope, and fit against existing gaps
• Recommendation: System Logs and Observability — justified by:
  • Prometheus is already deployed but broken (scrapes only itself)
  • Grafana being added needs real metrics to display
  • All five services (api1, api2, nginx, notification-worker, kafka) get instrumented — demonstrates cross-service observability, not just single-service metrics
  • No external credentials or risky refactoring required
  • Produces a live Grafana dashboard as a concrete, demonstrable artifact

Implementation plan (outlined in doc)

• Add prometheus-net.AspNetCore to the API; wire UseHttpMetrics() + MapMetrics()
• Custom business counters (trade_offers_created_total, trade_offers_accepted_total, trade_offers_rejected_total) in TradeOffersController
• MetricServer on port 9091 inside NotificationWorker
• nginx-prometheus-exporter sidecar in docker-compose.yml
• Updated prometheus.yml scraping all four service targets
• Grafana added to compose with auto-provisioned Prometheus datasource and dashboard

Options ruled out

Option	Why skipped
Redis caching	Solves a non-existent scale problem on SQLite
New microservice	Forces major refactoring without a clear business driver
Real email notifications	Adds external SMTP dependency; no new distributed systems concept
Kubernetes ingress	Scope jump unrelated to the current Docker Compose topology
Data sharding	SQLite can't shard natively; prerequisite migration dwarfs the feature

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