log4js-node

A port of log4js to node.js

View the Project on GitHub

File Appender

The file appender writes log events to a file. It supports an optional maximum file size, and will keep a configurable number of backups. When using the file appender, you should also call log4js.shutdown when your application terminates, to ensure that any remaining asynchronous writes have finished. Although the file appender uses the streamroller library, this is included as a dependency of log4js so you do not need to include it yourself.

Configuration

Any other configuration parameters will be passed to the underlying streamroller implementation (see also node.js core file streams):

Note that, from version 4.x of log4js onwards, the file appender can take any of the options for the dateFile appender as well. So you could roll files by both date and size.

Example

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

const logger = log4js.getLogger();
logger.debug('I will be logged in all-the-logs.log');

This example will result in a single log file (all-the-logs.log) containing the log messages.

Example with log rolling (and compressed backups)

log4js.configure({
  appenders: {
    everything: { type: 'file', filename: 'all-the-logs.log', maxLogSize: 10485760, backups: 3, compress: true }
  },
  categories: {
    default: { appenders: [ 'everything' ], level: 'debug'}
  }
});

This will result in one current log file (all-the-logs.log). When that reaches 10Mb in size, it will be renamed and compressed to all-the-logs.log.1.gz and a new file opened called all-the-logs.log. When all-the-logs.log reaches 10Mb again, then all-the-logs.log.1.gz will be renamed to all-the-logs.log.2.gz, and so on.