@nypl/node-lambda-boilerplate/src/utilities/Logger.js

An AWS node-lambda boilerplate written in ES7 via Babel that includes various configuration, testing, and deployment scripts

/* eslint-disable semi */
import winston from 'winston';

// Supress error handling
winston.emitErrs = true;

// Set default NYPL agreed upon log levels
const levels = {
  emergency: 0,
  alert: 1,
  critical: 2,
  error: 3,
  warning: 4,
  notice: 5,
  info: 6,
  debug: 7
};

const loggerTransports = [];

const getLogLevelCode = (levelString) => {
  switch (levelString) {
    case 'emergency':
      return 0;
    case 'alert':
      return 1;
    case 'critical':
      return 2;
    case 'error':
      return 3;
    case 'warning':
      return 4;
    case 'notice':
      return 5;
    case 'info':
      return 6;
    case 'debug':
      return 7;
    default:
      return 'n/a';
  }
};

if (process.env.NODE_ENV !== 'test') {
  loggerTransports.push(
    new winston.transports.Console({
      timestamp: () => {
        return new Date().toISOString();
      },
      formatter: (options) => {
        const result = {
          timestamp: options.timestamp(),
          levelCode: getLogLevelCode(options.level),
          level: options.level.toUpperCase()
        };

        if (process.pid) {
          result.pid = process.pid.toString();
        }

        if (options.message) {
          result.message = options.message;
        }

        if (options.meta && Object.keys(options.meta).length) {
          result.meta = JSON.stringify(options.meta);
        }

        return JSON.stringify(result);
      }
    })
  );
}

const logger = new (winston.Logger)({
  levels: levels,
  transports: loggerTransports,
  exitOnError: false
});

module.exports = logger;