Module Logger Pattern

Problem

Log entries from different modules are mixed in the output, making it hard to filter by origin. Each module should create its own logger with a fixed namespace so entries can be filtered without additional context.

Solution

import { Logit } from '@vielzeug/logit';

export const log = {
  api: Logit.scope('api'),
  auth: Logit.scope('auth'),
  db: Logit.scope('db'),
};

log.api.info('GET /users');
log.auth.warn('token expiring');

Pitfalls

• Using the same namespace string in two different modules makes their log entries indistinguishable. Use hierarchical namespaces (e.g., app:orders:service) to ensure uniqueness.
• Creating the logger at module load time means its namespace and bindings are fixed for that module instance. Prefer request-scoped child loggers when fields vary per request.
• Structured context is first-argument only: use logger.info({ userId }, 'event'). String-first calls accept only the message.

Related

• Child Logger Overrides
• Production Setup
• React Integration