/common-observability

name: common-observability
description: 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.
metadata:
  triggers:
    files:
      - "**/*.service.ts"
      - "**/*.handler.ts"
      - "**/*.middleware.ts"
      - "**/*.interceptor.ts"
      - "**/*.go"
      - "**/*.java"
      - "**/*.kt"
      - "**/*.py"
    keywords:
      - logging
      - tracing
      - metrics
      - opentelemetry
      - observability
      - slo

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)