Logger Utility (Winston-based)

A powerful, flexible logging utility built on winston, with support for:

• JSON or human-readable output
• Dynamic log levels per module
• Multiple transport types (daily rotation, static files, HTTP, etc.)
• Request-scoped context via AsyncLocalStorage (e.g., requestId)
• Exception handling and masking sensitive data

🔧 Setup

Install dependencies:

npm install winston winston-daily-rotate-file

Ensure your environment contains the logger config:

export LOGGER_CONFIG='{
  "levels": { "default": "debug", "auth.js": "info" },
  "format": "pretty",
  "transports": [
    { "type": "daily", "options": { "filename": "app", "datePattern": "YYYY-MM-DD", "maxFiles": "14d" } },
    { "type": "static", "options": { "filename": "combined.log" } }
  ]
}'

export LOGGER_CONFIG='{
  "levels": { "default": "info", "auth.js": "debug" },
  "format": "pretty",
  "transports": [
    { "type": "daily", "options": { "filename": "app", "datePattern": "YYYY-MM-DD", "maxFiles": "14d" } },
    { "type": "static", "options": { "filename": "combined.log", "maxSize": 5242880, "maxFiles": 5 } },
    { "type": "http", "options": { "host": "logserver.example.com", "port": 9000, "path": "/logs", "ssl": false } },
    { "type": "file", "options": { "filename": "errors.log", "level": "error" } },
    { "type": "file", "options": { "filename": "silly.log", "level": "silly" } }
  ]
}'

🧪 Example Test App

See logger-test-app.js for a basic Express server that demonstrates logging.

node logger-test-app.js

Visit:

• http://localhost:3000 → Basic log messages
• http://localhost:3000/error → Logs exception with stack trace

🧱 API

createLogger(fileName: string)

Returns a configured Winston logger instance tagged with the provided filename/module name.

requestContext.run({ requestId }, () => fn)

Run code with a request ID attached to logs using AsyncLocalStorage. Use inside middleware.

📁 Logs Structure

• /logs/app-YYYY-MM-DD.log → Rotating daily logs
• /logs/combined.log → Static log file
• /logs/exceptions.log → Uncaught exceptions
• /logs/errors.log → Error-level logs only

💡 Tips

• Use logger.debug/info/warn/error() depending on severity.
• Sensitive values like password or token are masked in pretty logs.
• Easily plug into any framework like Express, Koa, etc.

📜 License

MIT License © 2025 @vijevira (Vijendra Kumar)