NestJS Observability

采用 Pino 进行结构化日志记录，同时集成 Prometheus 指标监控。

SKILL.md

--- frontmatter

name: NestJS Observability
description: Structured logging (Pino) and Prometheus metrics.
metadata:
  labels: [nestjs, logging, monitoring, pino]
  triggers:
    files: ['main.ts', '**/*.module.ts']
    keywords: [nestjs-pino, Prometheus, Logger, reqId]

Observability Standards

Priority: P1 (OPERATIONAL)

Logging, monitoring, and observability patterns for production applications.

•
Standard: Use nestjs-pino for high-performance JSON logging.
- •Why: Node's built-in console.log is blocking and unstructured.
•
Configuration:
- •Redaction: Mandatory masking of sensitive fields (password, token, email).
- •Context: Always inject Logger and set the context (LoginService).

Tracing (Correlation)

•
Request ID: Every log line must include a reqId (Request ID).
- •nestjs-pino handles this automatically using AsyncLocalStorage.
- •Propagation: Pass x-request-id to downstream microservices/database queries key to trace flows.

Metrics

•Exposure: Use @willsoto/nestjs-prometheus to expose /metrics for Prometheus scraping.
•
Key Metrics:
1. •http_request_duration_seconds (Histogram)
2. •db_query_duration_seconds (Histogram)
3. •memory_usage_bytes (Gauge)

Health Checks

•
Terminus: Implement explicit logic for "Liveness" (I'm alive) vs "Readiness" (I can take traffic).
- •DB Check: TypeOrmHealthIndicator / PrismaHealthIndicator.
- •Memory Check: Fail if Heap > 300MB (prevent crash loops).