rest-api-starter/app/logger.js

Rest API starter kit.

/**
 * Created by svinci on 11/27/16.
 */
'use strict';

const configuration = require('config');
const winston = require('winston');

/**
 * Transaction store.
 */
const localStore = require('./local-store');

/**
 * Retrieve current transaction's id.
 */
const getTransactionId = () => localStore.getValue('tid', '-');

/**
 * Log levels priority definitions.
 * @type {{debug: number, info: number, warn: number, warning: number, error: number, off: number}}
 */
const logLevelWeights = {
    'debug': 1,
    'info': 2,
    'warn': 3,
    'warning': 3,
    'error': 4,
    'off': 5
};

/**
 * Message formatter function.
 * @param options
 * @returns {string}
 */
const formatter = (options) => {
    const message = options.message ? options.message : '';
    return `${options.timestamp()} [${options.level.toUpperCase()}] - [tid: ${getTransactionId()}] - ${message}`;
};

/**
 * File transport builder.
 * @param transport
 */
const getFileTransport = (transport) => new winston.transports.File({
    'name': 'file-transport',
    'handleExceptions': false,
    'json': false,
    'level': configuration.get('app.log.level'),
    'filename': transport.filename,
    'timestamp': () => new Date().toISOString(),
    'formatter': formatter
});

/**
 * Console transport builder.
 */
const getConsoleTransport = () => new winston.transports.Console({
    'name': 'console-transport',
    'handleExceptions': false,
    'json': false,
    'level': configuration.get('app.log.level'),
    'timestamp': () => new Date().toISOString(),
    'formatter': formatter
});

/**
 * Get all configured transports.
 */
const getTransports = () => configuration.get('app.log.transports')
    .map((transport) => {
        if (transport.type === 'file') {
            return getFileTransport(transport);
        }
        return getConsoleTransport();
    });

/**
 * Check if the given level is enabled.
 * @param level
 * @returns {boolean}
 */
const isLevelEnabled = (level) => {
    const levelWeight = logLevelWeights[level];
    const currentLevelWeigh = logLevelWeights[configuration.get('app.log.level')];
    return levelWeight && levelWeight >= currentLevelWeigh;
};

/**
 * Global logger. Lazy initialization.
 */
let logger = null;

/**
 * Create a wrapper of winston's logger.
 * @param name Logger's name.
 * @returns {{debug: (function(*)), isDebugEnabled: (function(): boolean), info: (function(*): (*|void)), isInfoEnabled: (function(): boolean), warn: (function(*): (*|void)), isWarnEnabled: (function(): boolean), warning: (function(*): (*|void)), isWarningEnabled: (function(): boolean), error: (function(*)), isErrorEnabled: (function(): boolean)}}
 */
module.exports = (name) => {

    if (!logger) {
        // Lazy initialization of global logger.
        const transports = getTransports();
        logger = new winston.Logger({
            'transports': transports,
            'exitOnError': false
        });
    }

    return {
        'debug': (msg) => logger.debug(`[${name}] ${msg}`),
        'isDebugEnabled': () => isLevelEnabled('debug'),

        'info': (msg) => logger.info(`[${name}] ${msg}`),
        'isInfoEnabled': () => isLevelEnabled('info'),

        'warn': (msg) => logger.warn(`[${name}] ${msg}`),
        'isWarnEnabled': () => isLevelEnabled('warn'),

        'warning': (msg) => logger.warn(`[${name}] ${msg}`),
        'isWarningEnabled': () => isLevelEnabled('warning'),

        'error': (msg) => logger.error(`[${name}] ${msg}`),
        'isErrorEnabled': () => isLevelEnabled('error')
    };

};