# Common Observability

> Enforce structured JSON logging, OpenTelemetry distributed tracing, and RED metrics across backend services. Use when adding request correlation, setting up tracing spans, defining SLO burn-rate alerts, or instrumenting middleware.

- Skill: `hoangnguyen0403/common-observability` (Agent Skill, multi-file: 4 files)
- Install (CLI): `npx skillmds@latest add hoangnguyen0403/common-observability`
- Raw SKILL.md: https://api.skillmd.com/api/skills/hoangnguyen0403/common-observability/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: HoangNguyen0403 (https://skillmd.com/u/hoangnguyen0403)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/hoangnguyen0403/common-observability

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# Common Observability Standards

## **Priority: P1 (HIGH)**

## Logging & Tracing

- **JSON Logs**: Always emit JSON structured logs. Never plain-text in prod.
- **Correlation**: Extract `X-Request-Id` or `traceparent`. Attach to async context.
- **Tracing**: Use OpenTelemetry. Propagate W3C `traceparent`.
- **Spans**: Name spans like `<HTTP_METHOD> <route>` (`GET /users/:id`).

See [implementation examples](references/implementation.md) for structured logger setup with Pino.

## Metrics

- **Required**: Request rate, Error rate, Latency histogram (p50/p95/p99), Saturation.
- **SLOs**: Alert on SLO burn rates, not raw threshold spikes.

## Instrumentation Workflow

1. Define the operation and route-normalized span name before adding code.
2. Propagate request/trace context across every async or service boundary.
3. Log one structured event with correlation fields; redact secrets and request bodies.
4. Add RED metrics with route-safe labels, then define an SLO and burn-rate alert.
5. Exercise a success and failure path; confirm spans close and IDs join logs to traces.

## Anti-Patterns

- **Console.log**: not use in prod; use structured logger (`pino`, `zap`).
- **PII in Logs**: Never log tokens, passwords, or full request bodies.
- **Dynamic Span Names**: `GET /users/123` causes cardinality explosion. Use `GET /users/:id`.
- **Missing Cleanup**: Always end tracing spans.

## References

- [Observability Data Formats](references/observability-formats.md)