market-data-service/utils/logger.js

const winston = require('winston');
const path = require('path');

// Define log levels
const logLevels = {
  error: 0,
  warn: 1,
  info: 2,
  http: 3,
  debug: 4,
};

// Define log colors
const logColors = {
  error: 'red',
  warn: 'yellow',
  info: 'green',
  http: 'magenta',
  debug: 'white',
};

winston.addColors(logColors);

// Create logs directory if it doesn't exist
const fs = require('fs');
const logDir = path.join(__dirname, '../logs');
if (!fs.existsSync(logDir)) {
  fs.mkdirSync(logDir, { recursive: true });
}

// Define log format
const logFormat = winston.format.combine(
  winston.format.timestamp({ format: 'YYYY-MM-DD HH:mm:ss' }),
  winston.format.errors({ stack: true }),
  winston.format.json(),
  winston.format.printf(({ timestamp, level, message, stack, ...meta }) => {
    let log = `${timestamp} [${level.toUpperCase()}]: ${message}`;

    if (Object.keys(meta).length > 0) {
      log += ` | ${JSON.stringify(meta)}`;
    }

    if (stack) {
      log += `\n${stack}`;
    }

    return log;
  })
);

// Create console format for development
const consoleFormat = winston.format.combine(
  winston.format.colorize({ all: true }),
  winston.format.timestamp({ format: 'HH:mm:ss' }),
  winston.format.printf(({ timestamp, level, message, ...meta }) => {
    let log = `${timestamp} [${level}]: ${message}`;

    if (Object.keys(meta).length > 0) {
      log += ` | ${JSON.stringify(meta)}`;
    }

    return log;
  })
);

// Create the logger instance
const logger = winston.createLogger({
  level: process.env.LOG_LEVEL || 'info',
  levels: logLevels,
  format: logFormat,
  defaultMeta: { service: 'financial-data-server' },
  transports: [
    // Write all logs with importance level of `error` or less to `error.log`
    new winston.transports.File({
      filename: path.join(logDir, 'error.log'),
      level: 'error',
      maxsize: 5242880, // 5MB
      maxFiles: 5,
    }),
    // Write all logs with importance level of `info` or less to `combined.log`
    new winston.transports.File({
      filename: path.join(logDir, 'combined.log'),
      maxsize: 5242880, // 5MB
      maxFiles: 5,
    }),
  ],
});

// If we're not in production, log to the console as well
if (process.env.NODE_ENV !== 'production') {
  logger.add(new winston.transports.Console({
    format: consoleFormat,
    level: process.env.LOG_LEVEL || 'debug',
  }));
}

// Create a stream object for Morgan HTTP logger
const stream = {
  write: (message) => {
    logger.http(message.trim());
  },
};

// Handle uncaught exceptions and unhandled rejections
logger.exceptions.handle(
  new winston.transports.File({
    filename: path.join(logDir, 'exceptions.log')
  })
);

logger.rejections.handle(
  new winston.transports.File({
    filename: path.join(logDir, 'rejections.log')
  })
);

// Graceful shutdown
process.on('SIGTERM', () => {
  logger.info('SIGTERM received, shutting down gracefully');
  logger.end(() => {
    process.exit(0);
  });
});

process.on('SIGINT', () => {
  logger.info('SIGINT received, shutting down gracefully');
  logger.end(() => {
    process.exit(0);
  });
});

module.exports = {
  logger,
  stream
};