kafka-pub-sub/config/winstonKafkaLogger.js

Enterprise-grade Kafka publish/subscribe library for Node.js — producer pool, batch sending, DLQ, SSL/SASL, multi-broker, and real-world industry examples.

const { logLevel } = require('kafkajs');
const winston = require('winston');
const DailyRotateFile = require('winston-daily-rotate-file');

const toWinstonLogLevel = (level) => {
  switch (level) {
    case logLevel.ERROR:
    case logLevel.NOTHING:
      return 'error';
    case logLevel.WARN:
      return 'warn';
    case logLevel.INFO:
      return 'info';
    case logLevel.DEBUG:
      return 'debug';
    default:
      return 'info';
  }
};

/**
 * Structured JSON log format with timestamp and correlation metadata.
 */
const jsonFormat = winston.format.combine(
  winston.format.timestamp({ format: 'YYYY-MM-DDTHH:mm:ss.SSSZ' }),
  winston.format.errors({ stack: true }),
  winston.format.json(),
);

/**
 * Human-readable format for console output.
 */
const consoleFormat = winston.format.combine(
  winston.format.timestamp({ format: 'YYYY-MM-DDTHH:mm:ss' }),
  winston.format.colorize(),
  winston.format.printf(({ timestamp, level, message, namespace, ...meta }) => {
    const ns = namespace ? `[${namespace}] ` : '';
    const extra = Object.keys(meta).length ? ` ${JSON.stringify(meta)}` : '';
    return `${timestamp} ${level}: ${ns}${message}${extra}`;
  }),
);

// eslint-disable-next-line no-shadow
const WinstonLogCreator = (logLevel) => {
  const resolvedLevel = toWinstonLogLevel(logLevel);

  const logger = winston.createLogger({
    level: resolvedLevel,
    defaultMeta: { service: 'kafka-pub-sub' },
    transports: [
      new winston.transports.Console({
        format: consoleFormat,
        silent: process.env.NODE_ENV === 'test', // suppress in tests
      }),
      new DailyRotateFile({
        filename: 'logs/kafka-%DATE%.log',
        datePattern: 'YYYY-MM-DD',
        zippedArchive: true,
        maxSize: '20m',
        maxFiles: '14d', // retain 14 days
        format: jsonFormat,
      }),
      new DailyRotateFile({
        level: 'error',
        filename: 'logs/kafka-error-%DATE%.log',
        datePattern: 'YYYY-MM-DD',
        zippedArchive: true,
        maxSize: '10m',
        maxFiles: '30d', // retain 30 days for errors
        format: jsonFormat,
      }),
    ],
  });

  return ({ namespace, level, label, log }) => {
    const { message, ...extra } = log;
    logger.log({
      level: toWinstonLogLevel(level),
      message,
      namespace,
      label,
      ...extra,
    });
  };
};

module.exports = WinstonLogCreator;