winston

import { createLogger, format, transports, Logger } from 'winston'; // Create a logger instance const logger: Logger = createLogger({ level: 'info', // Set the default logging level format: format.json(), // Use JSON format for structured logs defaultMeta: { service: 'user-service' }, // Default metadata for all logs transports: [ // Transport for error-level logs and higher to a dedicated file new transports.File({ filename: 'error.log', level: 'error' }), // Transport for info-level logs and higher to a combined file new transports.File({ filename: 'combined.log' }) ] }); // Add a console transport if not in production environment if (process.env.NODE_ENV !== 'production') { logger.add(new transports.Console({ format: format.combine( format.colorize(), // Add color to the console output format.simple() // Use a simple format for console readability ) })); } // Example log messages logger.info('Application started successfully.', { transactionId: 'txn-123' }); logger.warn('A potential configuration issue was detected.', { configPath: '/app/config.js' }); logger.error('Failed to connect to the database.', new Error('Connection refused by DB server.')); logger.debug('This debug message will not appear in production logs.'); // Simulate an async operation and log its completion async function performTask() { logger.info('Starting critical task...'); await new Promise(resolve => setTimeout(resolve, 1000)); // Simulate work logger.info('Critical task completed.', { durationMs: 1000 }); } performTask();