Winston: how to rotate logs

winston author and maintainer here.

Logging to a new file everyday is currently an open feature request: https://github.com/flatiron/winston/issues/10. Would love to see someone implement it.

That said, there are other options:

1. The File transport accepts a maxsize option which will rotate the logfile when it exceeds a certain size in bytes.

2. There is also an open pull-request with a new transport I haven't had a chance to really dig into "fileRotate", which it seems does this kind of date-based rotation: https://github.com/flatiron/winston/pull/120/files

The feature is present and we are using it in production, winston.transports.DailyRotateFile:

var timeFormatFn = function() {
    'use strict';
    return moment().format(cfg.timeFormat);
};

var logger = new(winston.Logger)({
    exitOnError: false,
    transports: [
        new(winston.transports.DailyRotateFile)({
            filename: cfg.appLogName,
            dirname: __dirname + '/../' + cfg.logsDirectory,
            datePattern: cfg.rollingDatePattern,
            timestamp: timeFormatFn
        }),
        new(winston.transports.Console)({
            colorize: true,
            timestamp: timeFormatFn
        })
    ]
});

You can use the following code to rotate the log files daily:

var winston = require('winston');
require('winston-daily-rotate-file');
var transport = new (winston.transports.DailyRotateFile)({
    filename: './log',
    datePattern: 'yyyy-MM-dd.',
    prepend: true,
    level: 'info'
});
var logger = new (winston.createLogger)({
    transports: [
      transport
    ]
});
logger.info('Hello World!');