zlog4js v1.0.5

zlog

This is a logger for Node.js inspired by log4j used in Java.

Zlog can define logger and child loggers. It can be enhanced with custom appenders.

Quick Start

Install the library:

npm install zlog4js --save

Setup the logger in your application:

const zlog = require('zlog4js');
zlog.setRootLogger('ALL');

console.log('This should be wrapped via zlog');

Development

Install Dependencies:

npm install

Run tests:

npm test

Principle

There are 4 main entities working together:

Appenders

Define your appenders. Appenders will append the logged message in a chosen format. Appenders can be ConsoleAppender, FileAppender, customAppender.

Loggers

Define your logger with a name and a log level as well as which appenders they use. Use the logger in your code.

logManager

The logManager helps you access and define your appenders and loggers.

pattern

Appenders will output the text in a pattern. Ex: 12:13 myLogger INFO myText

format

Appenders will output the text following a format before including the text in the appender pattern.

logger.info('Hello %b','you');

actually runs

zlog.formatText('Hello %b','you')

Result: Hello you

Basic scenario

A named logger shall be retrieved in the file containing the code to log. Though it might be pratical to configure the logger from this file, best is to define appenders and loggers in a dedicated file of your application for quick access and overall vision of what and how all is logged.

const zlog = require('zlog4js');
var logger = zlog.getLogger('do.service');
logger.info('Some info')'
logger.debug('I am debugging')'

This will display the message to the console by default

In order to modify the log level:

logger.setLevel('INFO');

or

zlog.setLogger('do.service','INFO');

set the log level

Log levels

• all // logger would log anything
• debug
• info
• warn
• error
• fatal
• none

Appenders

Loggers push information, errors, warning, etc, to appenders which output the data to the console, to file or to a remote server according to their implementations.

STDOUT appender

By default, all loggers will user the STDOUT appender which outputs to console.

File Appender

A basic file appender is provided.

ex:

setFileAppender('FILE_APPENDER', '/home/user/logs/log.txt');

zlog.setLogger('myLogger','ALL',['FILE_APPENDER']);
var logger = zlog.getLogger('myLogger');
logger.info('Hello world');

In this example, any information sent to myLogger would be persisted by FILE_APPENDER in the provided file.

Custom appender

ex:

function MyAppender() {
    this.writeLog = function(loggerName, logLevel, logText) {
        sentLogToRemoveServerOfMyChoice(loggerName+' '+logLevel+' '+logText);
    }
}

zlog.setRootLogger('ALL',['STDOUT','MYAPPENDER']);
var logger = zlog.getLogger('myLogger');
logger.info('Hello world');

In addition to the console appender STDOUT, information would also be logged by MYAPPENDER, so the sentLogToRemoveServerOfMyChoice function would be called.

Logging strategy

Default appender

if a logger does not have appenders, it will default to the parent loggers. If there is no parent logger. the rootLogger appender will be used.

Default logger

Using console.log, error, etc will output to the default logger named ROOT which use the STDOUT console appender.

zlog.setRootLogger('INFO');

This would set the default root logger level.

Logger prioritization

Ex:

In the following example, myLogger would write the text in its appender.

zlog.setLogger('myLogger','NONE',['MYAPPENDER']);
zlog.setLogger('myLogger/childLogger','INFO');
var logger = zlog.getLogger('myLogger/childLogger');
logger.info('Hello world');

MyLogger has an appender. it will write the text because the child logger is set to a level.

if the rootLogger was set to NONE. It would also still write the text as force by the child logger level.

Ex 2:

In the following example, myLogger would not write anything.

zlog.setLogger('myLogger','NONE',['MYAPPENDER']);
zlog.setLogger('myLogger/childLogger');
var logger = zlog.getLogger('myLogger/childLogger');
logger.info('Hello world');

if the childLogger was NOT set with a level, it would write according to its parent level.

Ex 3:

In the following example, myLogger would not write anything.

zlog.setLogger('myLogger','ERROR',['MYAPPENDER']);
zlog.setLogger('myLogger/childLogger');
var logger = zlog.getLogger('myLogger/childLogger');
logger.info('Hello world');

if the childLogger was not set with a level, it would write according to its parent logger level. In this example, myLogger would not write the text because the parent logger level is lower.