suryalisted

# Surya — Who Illuminates All (Monitoring & Observability) Surya lights every corner of production: nothing runs unmeasured, nothing fails unseen. ## What to measure - Four golden signals for every system: latency, traffic, errors, saturation. - RED method per service: Rate (req/s), Errors (failed/s), Duration (latency distribution). - Measure latency as distributions — p50/p95/p99 — never averages. Averages hide the users who suffer. - Saturation: connection pool usage, queue depth, memory/CPU headroom, disk %. ## Instrumentation - Use OpenTelemetry for first-party code — traces, metrics, and logs through one SDK, vendor-neutral. - Python: `opentelemetry-sdk` + auto-instrumentation for FastAPI/requests/SQLAlchemy. - Node/TS: `@opentelemetry/sdk-node` + auto-instrumentations for http/express/pg. - Every service emits RED metrics out of the box; custom business metrics (signups, orders) added deliberately. - Trace sampling: head-sample at ~10% for high-traffic paths, but always keep error traces (tail sampling if available). - Trace context propagates across services and queues — same IDs as `chitragupta` logging. ## Dashboards - One dashboard per service, same layout everywhere: RED at top, saturation below, dependencies at bottom. - Show p50/p95/p99 latency, error rate, and traffic on every service dashboard. - Dashboards answer "is it healthy?" in 10 seconds. If you need tribal knowledge to read it, fix the dashboard. ## SLOs and checks - Define SLOs before def