How to add new appenders dynamically.

[mai1x9]

Programatically how can we add new appenders to log to new file. I want to make general function where i can create new logger with proper names and write to its own file.

But log4js seems to be called only once.

I wrote a general code,

class Logger{
  /**
   * General logger class
   * name: Name of the logger.
   * options is JSON with keys
   * filename|level|maxsize|backups
   */
  constructor(name="", options={}) {
    options.filename = options.filename || "errors.log"

    let __log4js = require("log4js")
    __log4js.configure({
      appenders: {
          default: {
            type: 'file',
            filename: '/home/ubuntu/default-errors.log',
            maxLogSize: '5M',
            backups: 6,
            compress: true
          },
          console: { type: 'console' },
          [name]:  {
            type: "file",
            filename: path.join(__logdir, options.filename),
            maxLogSize: options.maxsize || process.env.LOG_MAX_SIZE || "5M",
            backups: options.backups || +process.env.LOG_MAX_BACKUPS || 6,
            compress: true,
          }
      },
      categories: { 
          default: { 
              appenders: [ 'default' ], level: 'debug' 
          },
          [name]: {
            appenders: [name],
            level: options.level || process.env.LOG_LEVEL || "debug",
          }
      }
    })

    this.logger = __log4js.getLogger(name);
    debug(`Created new logger instance with the log name: ${name}, logs will be saved at: ${__logdir ? path.join(__logdir, options.filename) : path.join(homedir, ".logs", options.filename)}`)
  }
}

Using this class providing log name, and file path, i wanted to create multiple log instances and log to sep files dynamically. Different files may have different log methods.

But this does not seem working as some times it does not get logged. I do not know why ?

[lamweili]

If you maintain a copy of your configuration, you can modify it and reload log4js by log4js.configure(config).

var log4js = require('log4js');
var logger = log4js.getLogger();

// load config
var config = {
 appenders: {
   out1: { type: 'stdout' },
 },
 categories: {
   default: { 
     appenders: [ 'out1' ],
     level: 'all'
   }
 }
};
log4js.configure(config);

logger.info("hello should appear once");

// adding new appenders
config.appenders.out2 = { type: 'stdout' };
config.categories.default.appenders.push('out2');

// reload config
log4js.configure(config);

logger.info("hello should appear twice");

[mai1x9]

If you maintain a copy of your configuration, you can modify it and reload log4js but log4js.configure(config).

var log4js = require('log4js');
var logger = log4js.getLogger();

// load config
var config = {
 appenders: {
   out1: { type: 'stdout' },
 },
 categories: {
   default: { 
     appenders: [ 'out1' ],
     level: 'all'
   }
 }
};
log4js.configure(config);

logger.info("hello should appear once");

// adding new appenders
config.appenders.out2 = { type: 'stdout' };
config.categories.default.appenders.push('out2');

// reload config
log4js.configure(config);

logger.info("hello should appear twice");

Thanks @lamweili infact I have done same way. maintain copy of configurations and reload everytime when dynamically required.
That works. Thanks for reply.

[lamweili]

Please close the issue if it has been resolved. Thanks!