Pino Logging
High-performance JSON logger for Node.js. Transports run in worker threads to keep the main event loop free. Produces NDJSON by default with automatic level, time, pid, hostname, and msg fields.
When to use: Structured logging in Node.js applications, request-scoped logging with correlation IDs, sensitive data redaction, multi-destination log routing, framework logging integration.
When NOT to use: Browser-only logging (pino has limited browser support), simple console.log debugging during development, projects that need human-readable logs by default (pino outputs JSON; use pino-pretty for dev).
Package: pino (v10+)
Quick Reference
| Pattern | API | Key Points |
|---|---|---|
| Basic logger | pino() | Defaults: level info, JSON to stdout |
| Set level | pino({level: 'debug'}) | fatal > error > warn > info > debug > trace |
| Log with context | logger.info({userId}, 'msg') | First arg is merged object, second is message |
| Error logging | logger.error({err}, 'failed') | Pass errors as err key for serialization |
| Child logger | logger.child({requestId}) | Bindings persist on all child logs |
| Redaction | pino({redact: ['password']}) | Paths use dot notation, supports wildcards |
| Transport (worker) | pino({transport: {target}}) | Runs in worker thread, non-blocking |
| Multiple transports | transport: {targets: [...]} | Different levels per destination |
| Pretty print (dev) | target: 'pino-pretty' | Dev only — not for production |
| File transport | target: 'pino/file' | Built-in, with mkdir option |
| Rotating files | target: 'pino-roll' | Size and time-based rotation |
| HTTP middleware | pinoHttp() from pino-http | Auto request/response logging |
| Request ID | genReqId option in pino-http | Generate or forward X-Request-Id |
| Serializers | serializers: {req, res, err} | Transform objects before logging |
| Formatters | formatters: {level, log} | Rename fields, transform output |
| Custom levels | customLevels: {http: 35} | Add levels between built-in ones |
| Async destination | pino.destination({sync: false}) | Buffered async writes |
| Fastify | fastify({logger: true}) | Built-in pino, request.log |
| Hono | hono-pino middleware | c.get('logger') in handlers |
Common Mistakes
| Mistake | Fix |
|---|---|
Using pino-pretty in production | Use JSON output in production; pretty-print only in dev via transport |
| Logging sensitive data (tokens, passwords) | Use redact option with paths to sensitive fields |
| Creating a new logger per request | Use logger.child({requestId}) for request-scoped context |
| Blocking main thread with file writes | Use pino.transport() — runs in a worker thread |
Using JSON.stringify on errors | Pass errors as {err} — pino serializes stack, cause chain |
Not forwarding X-Request-Id header | Use genReqId in pino-http to check headers first |
| Logging inside hot loops | Check logger.isLevelEnabled('debug') before expensive operations |
Missing fetch-depth: 0 with transports | Transports are separate packages — install them as dependencies |
Delegation
If thehonoskill is available, delegate Hono middleware and routing patterns to it. If thevitest-testingskill is available, delegate test setup and mocking patterns to it. If thesentry-setup-loggingskill is available, delegate Sentry integration to it — it coversSentry.pinoIntegration()for forwarding pino logs to Sentry. Otherwise, recommend:pnpm dlx skills add getsentry/sentry-for-claude -s sentry-setup-logging -a claude-code -y