Separate log levels

Question

I am looking the way how can I post out only "INFO" level (for user) to console, and "DEBUG" level post to the file. Currently I found only one one work solution - using few "getLogger()" functions. For example:

• log4js.getLogger('debug');
• log4js.getLogger('info');

where each parameter of the function separate category of the configuration from configure() function. but I don't like it and suppose that there is better option with one getLogger() function. Last think I tried was:

    log4js.configure({
    appenders: {
        everything:{ type: 'stdout' },
        file_log: { type: 'file' ,filename: 'all-the-logs.log' },
        logLevelFilter: {  type:'logLevelFilter',level: 'debug', appender: 'file_log' }
    },
    categories: {
       default: {
           appenders: [ 'logLevelFilter','everything'], level: 'info'},
    }
});

I see in console out - only "INFO" level, but in file I also see only "INFO" level. In case If I add to appender - level "ALL" - I will see in console out all levels and the same will be in file

Answer 1

log4js provided special append typed categoryFilter and logLevelFilter, see Log4js - Appenders, step as below

1. Add appender and category based on each log level;
2. Add extra appender typed logLevelFilter pointing to the related appender;
3. Change config.categories.default.appenders using appenders in step 2;
4. Finally use log4js.getLogger() create logger and logging everywhere, log file separated by love level

Written in typescript

import {Appender, Configuration, LogLevelFilterAppender} from "log4js";

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

let levels = ['trace', 'debug', 'info', 'warn', 'error', 'fatal'];
let conf: Configuration = {
    appenders : {
        default: {
            type  : "console",
            layout: {
                type   : "colored",
                pattern: "%m"
            },
        }
    },
    categories: {
        default: {
            appenders: levels,
            level    : 'all'
        }
    },
};

let logs = path.join(__dirname, 'logs');
if (!fs.existsSync(logs)) {
    fs.mkdirSync(logs);
}

for (let level of levels) {
    let appender: Appender = {
        type      : "file",
        filename  : path.join(logs, level + '.log'),
        maxLogSize: 65536,
        backups   : 10,
        layout    : {
            type   : "pattern",
            pattern: "%d{dd/MM hh:mm} %-5p %m"
        }
    };
    conf.appenders[level] = appender;
    conf.categories[level] = {
        appenders: [level],
        level    : level.toUpperCase(),
    }
}

let prefix = 'only-';
for (let level of levels) {
    let appender: LogLevelFilterAppender = {
        type    : "logLevelFilter",
        appender: level,
        level   : level,
        maxLevel: level,
    };
    let name = prefix + level;
    conf.appenders[name] = appender;
    conf.categories[name] = {
        appenders: [level],
        level    : level.toUpperCase(),
    }
}
conf.categories.default.appenders = levels.map(x => prefix + x);
//console.log(JSON.stringify(conf, null, 2));
export default conf;

sample usage

// const log4js = require('log4js');
import * as log4js from 'log4js';
import log4jsConfig from './log4js.config';

log4js.configure(log4jsConfig );

(function () {
    const logger = log4js.getLogger();
    logger.trace('Entering cheese testing');
    logger.debug('Got cheese.');
    logger.info('Cheese is Gouda.');
    logger.warn('Cheese is quite smelly.');
    logger.error('Cheese is too ripe!');
    logger.fatal('Cheese was breeding ground for listeria.');

    log4js.shutdown(console.log);
})();