pino

Q: Should I log errors with logger.error or throw?

Throw for control flow; log at the boundary that handles the error (HTTP error handler, worker catch). Log once with err key: log.error({ err, orderId }, "payment_failed").

Q: PII in logs?

Redact at config. Prefer opaque IDs (userId) over emails and names. If GDPR applies, define retention and scrubbing in the log platform, not in app code alone.

Pino is the default production logger for Node.js APIs: fast structured JSON, low overhead, and first-class Fastify integration.

Recipe

Quick-reference recipe card - copy-paste ready.

import pino from "pino";
 
export const logger = pino({
  level: process.env.LOG_LEVEL ?? "info",
  redact: ["req.headers.authorization", "password", "cookie"],
  base: { service: "orders-api", env: process.env.NODE_ENV },
});
 
logger.info({ event: "server_start", port: 3000 });

# Development only - never in production Dockerfile
npm install -D pino-pretty
LOG_LEVEL=debug node app.js | npx pino-pretty

When to reach for this:

Every production Node service (Express, Fastify, Nest, workers)
Centralized log aggregation (Datadog, CloudWatch, Loki, ELK)
Correlating requests with requestId across services

Working Example

// src/logger.ts
import pino from "pino";
 
export function createLogger() {
  return pino({
    level: process.env.LOG_LEVEL ?? "info",
    timestamp: pino.stdTimeFunctions.isoTime,
    redact: {
      paths: [
        "req.headers.authorization",
        "req.headers.cookie",
        "body.password",
        "body.token",
      ],
      censor: "[REDACTED]",
    },
    formatters: {
      level(label) {
        return { level: label };
      },
    },
  });
}
 
// src/middleware/request-context.ts
import type { Request, Response, NextFunction } from "express";
import { randomUUID } from "node:crypto";
import type { Logger } from "pino";
 
export function requestContext(log: Logger) {
  return (req: Request, res: Response, next: NextFunction) => {
    const requestId = (req.headers["x-request-id"] as string) ?? randomUUID();
    req.log = log.child({ requestId });
    res.setHeader("x-request-id", requestId);
    const start = Date.now();
    res.on("finish", () => {
      req.log.info({
        event: "request_complete",
        method: req.method,
        path: req.path,
        statusCode: res.statusCode,
        durationMs: Date.now() - start,
      });
    });
    next();
  };
}

// Express usage
import express from "express";
import { createLogger } from "./logger.js";
import { requestContext } from "./middleware/request-context.js";
 
const log = createLogger();
const app = express();
 
declare global {
  namespace Express {
    interface Request {
      log: import("pino").Logger;
    }
  }
}
 
app.use(requestContext(log));
app.get("/health", (req, res) => {
  req.log.debug({ event: "health_check" });
  res.json({ status: "ok" });
});

Production rules:

Log to stdout only - the container runtime ships logs
Never use pino-pretty in production images
Use child loggers per request, not global string concatenation
Log events as objects: { event: "order_created", orderId }

Fastify Integration

Fastify uses Pino by default:

import Fastify from "fastify";
 
const app = Fastify({
  logger: {
    level: "info",
    redact: ["req.headers.authorization"],
  },
});

See Logging with Pino for hooks, serializers, and request IDs.

Comparison

Logger	Use when	Skip when
Pino	JSON services, Fastify, high throughput	Legacy apps deeply tied to Winston transports
Winston	Existing Winston-only codebase	Greenfield APIs
console.log	Local spike only	Any deployed environment
Bunyan	Maintaining legacy services	New projects

FAQs

Should I log errors with logger.error or throw?

Throw for control flow; log at the boundary that handles the error (HTTP error handler, worker catch). Log once with err key: log.error({ err, orderId }, "payment_failed").

How do I log unhandled rejections?

process.on("unhandledRejection", (reason) => {
  logger.fatal({ err: reason }, "unhandled_rejection");
  process.exit(1);
});

Document exit policy per service - Kubernetes will restart the pod.

PII in logs?

Redact at config. Prefer opaque IDs (userId) over emails and names. If GDPR applies, define retention and scrubbing in the log platform, not in app code alone.

Logging with Pino - Fastify-specific patterns
Essential Libraries Basics - why Pino is default
Observability Basics - traces + logs correlation

npm Official Website & Registry - Package search, publishing, and documentation.
Node.js Best Practices (GitHub) - Curated production best practices.
NodeSource Blog & Resources - Enterprise Node.js performance and security content.
Node.js Cookbook, 5th Edition - Practical server-side recipes.
Node.js Design Patterns, 4th Edition - Production-grade application patterns.

Stack versions: This page was written for Node.js 24.18.0 (Active LTS), npm 10+, TypeScript 5.6+, Express 5, Fastify 5, and NestJS 11.

pino

Pino is the default production logger for Node.js APIs: fast structured JSON, low overhead, and first-class Fastify integration.

Recipe

Quick-reference recipe card - copy-paste ready.

import pino from "pino";
 
export const logger = pino({
  level: process.env.LOG_LEVEL ?? "info",
  redact: ["req.headers.authorization", "password", "cookie"],
  base: { service: "orders-api", env: process.env.NODE_ENV },
});
 
logger.info({ event: "server_start", port: 3000 });

# Development only - never in production Dockerfile
npm install -D pino-pretty
LOG_LEVEL=debug node app.js | npx pino-pretty

When to reach for this:

Every production Node service (Express, Fastify, Nest, workers)
Centralized log aggregation (Datadog, CloudWatch, Loki, ELK)
Correlating requests with requestId across services

Working Example

// src/logger.ts
import pino from "pino";
 
export function createLogger() {
  return pino({
    level: process.env.LOG_LEVEL ?? "info",
    timestamp: pino.stdTimeFunctions.isoTime,
    redact: {
      paths: [
        "req.headers.authorization",
        "req.headers.cookie",
        "body.password",
        "body.token",
      ],
      censor: "[REDACTED]",
    },
    formatters: {
      level(label) {
        return { level: label };
      },
    },
  });
}
 
// src/middleware/request-context.ts
import type { Request, Response, NextFunction } from "express";
import { randomUUID } from "node:crypto";
import type { Logger } from "pino";
 
export function requestContext(log: Logger) {
  return (req: Request, res: Response, next: NextFunction) => {
    const requestId = (req.headers["x-request-id"] as string) ?? randomUUID();
    req.log = log.child({ requestId });
    res.setHeader("x-request-id", requestId);
    const start = Date.now();
    res.on("finish", () => {
      req.log.info({
        event: "request_complete",
        method: req.method,
        path: req.path,
        statusCode: res.statusCode,
        durationMs: Date.now() - start,
      });
    });
    next();
  };
}

// Express usage
import express from "express";
import { createLogger } from "./logger.js";
import { requestContext } from "./middleware/request-context.js";
 
const log = createLogger();
const app = express();
 
declare global {
  namespace Express {
    interface Request {
      log: import("pino").Logger;
    }
  }
}
 
app.use(requestContext(log));
app.get("/health", (req, res) => {
  req.log.debug({ event: "health_check" });
  res.json({ status: "ok" });
});

Production rules:

Log to stdout only - the container runtime ships logs
Never use pino-pretty in production images
Use child loggers per request, not global string concatenation
Log events as objects: { event: "order_created", orderId }

Fastify Integration

Fastify uses Pino by default:

import Fastify from "fastify";
 
const app = Fastify({
  logger: {
    level: "info",
    redact: ["req.headers.authorization"],
  },
});

See Logging with Pino for hooks, serializers, and request IDs.

Comparison

Logger	Use when	Skip when
Pino	JSON services, Fastify, high throughput	Legacy apps deeply tied to Winston transports
Winston	Existing Winston-only codebase	Greenfield APIs
console.log	Local spike only	Any deployed environment
Bunyan	Maintaining legacy services	New projects

FAQs

Should I log errors with logger.error or throw?

Throw for control flow; log at the boundary that handles the error (HTTP error handler, worker catch). Log once with err key: log.error({ err, orderId }, "payment_failed").

How do I log unhandled rejections?

process.on("unhandledRejection", (reason) => {
  logger.fatal({ err: reason }, "unhandled_rejection");
  process.exit(1);
});

Document exit policy per service - Kubernetes will restart the pod.

PII in logs?

Redact at config. Prefer opaque IDs (userId) over emails and names. If GDPR applies, define retention and scrubbing in the log platform, not in app code alone.

Logging with Pino - Fastify-specific patterns
Essential Libraries Basics - why Pino is default
Observability Basics - traces + logs correlation

npm Official Website & Registry - Package search, publishing, and documentation.
Node.js Best Practices (GitHub) - Curated production best practices.
NodeSource Blog & Resources - Enterprise Node.js performance and security content.
Node.js Cookbook, 5th Edition - Practical server-side recipes.
Node.js Design Patterns, 4th Edition - Production-grade application patterns.

Stack versions: This page was written for Node.js 24.18.0 (Active LTS), npm 10+, TypeScript 5.6+, Express 5, Fastify 5, and NestJS 11.

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