log4js-node/docs/logstashUDP.md

Logstash UDP Appender

This appender sends log events to a logstash server via UDP. It uses the node.js core UDP support, and so requires no extra dependencies. Remember to call log4js.shutdown in your application if you want the UDP socket closed cleanly.

Configuration

• type - logstashUDP
• host - string - hostname (or IP-address) of the logstash server
• port - integer - port of the logstash server
• logType - string (optional) - used for the type field in the logstash data
• category - string (optional) - used for the type field of the logstash data if logType is not defined
• fields - object (optional) - extra fields to log with each event. User-defined fields can be either a string or a function. Functions will be passed the log event, and should return a string.
• layout - (optional, defaults to dummyLayout) - used for the message field of the logstash data (see layouts)
• args - (optional, defaults to both) - determines how to log arguments and configuration fields: direct logs them as direct properties of the log object, fields logs them as child properties of the fields property, and both logs both.

Example

log4js.configure({
  appenders: {
    logstash: {
      type: 'logstashUDP',
      host: 'log.server',
      port: '12345',
      logType: 'application',
      fields: { biscuits: 'digestive', tea: 'tetley', user: function(logEvent) {
          return AuthLibrary.currentUser();
        }
      }
    }
  },
  categories: {
    default: { appenders: ['logstash'], level: 'info' }
  }
});
const logger = log4js.getLogger();
logger.info("important log message", { cheese: 'gouda', biscuits: 'hobnob' });

This will result in a JSON message being sent to log.server:12345 over UDP, with the following format:

{
  '@version': '1',
  '@timestamp': '2014-04-22T23:03:14.111Z',
  'type': 'application',
  'message': 'important log message',
  'fields': {
    'level': 'INFO',
    'category': 'default',
    'biscuits': 'hobnob',
    'user': 'charlie',
    'cheese': 'gouda',
    'tea': 'tetley'
  }
}