syslog-client
TCP and UDP syslog client RFC 5424 & RFC 3164
Last updated 3 years ago by paulgrove .
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syslog-client

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This module is a pure JavaScript implementation of the BSD Syslog Protocol RFC 3164 and the Syslog Protocol RFC 5424.

This module is installed using node package manager (npm):

npm install syslog-client

It is loaded using the require() function:

var syslog = require("syslog-client");

TCP or UDP clients can then be created to log messages to remote hosts.

var client = syslog.createClient("127.0.0.1");

client.log("example message");

Constants

The following sections describe constants exported and used by this module.

syslog.Transport

This object contains constants for all valid values for the transport attribute passed to the options argument for the createClient() function. The following constants are defined in this object:

  • Tcp
  • Udp

syslog.Facility

This object contains constants for all valid values for the facility attribute passed to the options argument for the log() method on the Client class. The following constants are defined in this object:

  • Kernel - 0
  • User - 1
  • System - 3
  • Audit - 13
  • Alert - 14
  • Local0 - 16
  • Local1 - 17
  • Local2 - 18
  • Local3 - 19
  • Local4 - 20
  • Local5 - 21
  • Local6 - 22
  • Local7 - 23

syslog.Severity

This object contains constants for all valid values for the severity attribute passed to the options argument for the log() method on the Client class. The following constants are defined in this object:

  • Emergency - 0
  • Alert - 1
  • Critical - 2
  • Error - 3
  • Warning - 4
  • Notice - 5
  • Informational - 6
  • Debug - 7

Using This Module

All messages are sent using an instance of the Client class. This module exports the createClient() function which is used to create instances of the Client class.

syslog.createClient([target], [options])

The createClient() function instantiates and returns an instance of the Client class:

// Default options
var options = {
	syslogHostname: os.hostname(),
	transport: syslog.Transport.Udp,
	port: 514
};

var client = syslog.createClient("127.0.0.1", options);

The optional target parameter defaults to 127.0.0.1. The optional options parameter is an object, and can contain the following items:

  • port - TCP or UDP port to send messages to, defaults to 514
  • syslogHostname - Value to place into the HOSTNAME part of the HEADER part of each message sent, defaults to os.hostname()
  • tcpTimeout - Number of milliseconds to wait for a connection attempt to the specified Syslog target, and the number of milliseconds to wait for TCP acknowledgements when sending messages using the TCP transport, defaults to 10000 (i.e. 10 seconds)
  • transport - Specify the transport to use, can be either syslog.Transport.Udp or syslog.Transport.Tcp, defaults to syslog.Transport.Udp
  • facility - set default for client.log(); default is syslog.Facility.Local0.
  • severity - set default for client.log(); default is syslog.Severity.Informational.
  • rfc3164 - set to false to use RFC 5424 syslog header format; default is true for the older RFC 3164 format.
  • appName - set the APP-NAME field when using rfc5424; default uses process.title
  • dateFormatter - change the default date formatter when using rfc5424; interface: function(date) { return string; }; defaults to function(date) { return date.toISOString(); }

client.on("close", callback)

The close event is emitted by the client when the clients underlying TCP or UDP socket is closed.

No arguments are passed to the callback.

The following example prints a message to the console when a clients underlying TCP or UDP socket is closed:

client.on("close", function () {
	console.log("socket closed");
});

client.on("error", callback)

The error event is emitted by the client when the clients underlying TCP or UDP socket emits an error.

The following arguments will be passed to the callback function:

  • error - An instance of the Error class, the exposed message attribute will contain a detailed error message.

The following example prints a message to the console when an error occurs with a clients underlying TCP or UDP socket:

client.on("error", function (error) {
	console.error(error);
});

client.close()

The close() method closes the clients underlying TCP or UDP socket. This will result in the close event being emitted by the clients underlying TCP or UDP socket which is passed through to the client, resulting in the client also emitting a close event.

The following example closes a clients underlying TCP or UDP socket:

client.close();

client.log(message, [options], [callback])

The log() method sends a Syslog message to a remote host.

The message parameter is a string containing the message to be logged.

The optional options parameter is an object, and can contain the following items:

  • facility - Either one of the constants defined in the syslog.Facility object or the facility number to use for the message, defaults to syslog.Facility.Local0 (see syslog.createClient())
  • severity - Either one of the constants defined in the syslog.Severity object or the severity number to use for the message, defaults to syslog.Severity.Informational (see syslog.createClient())
  • rfc3164 - set to false to use RFC 5424 syslog header format; default is true for the older RFC 3164 format.
  • timestamp - Optional Javascript Date() object to back-date the message.
  • msgid - Optional RFC 5424 message-id.

The callback function is called once the message has been sent to the remote host, or an error occurred. The following arguments will be passed to the callback function:

  • error - Instance of the Error class or a sub-class, or null if no error occurred

Each message sent to the remote host will have a newline character appended to it, if one is not already appended. Care should be taken to ensure newline characters are not embedded within the message passed to this method (i.e. not appearing at the end), as this may cause some syslog relays/servers to incorrectly parse the message.

The following example sends a message to a remote host:

var options = {
	facility: syslog.Facility.Daemon,
	severity: syslog.Severity.Critical
};

var message "something is wrong with this daemon!";

client.log(message, options, function(error) {
	if (error) {
		console.error(error);
	} else {
		console.log("sent message successfully");
	}
});

Example Programs

Example programs are included under the modules example directory.

Running tests and test coverage

Tests can be run with:

npm test

Install dev dependencies before running test coverage:

npm install --dev
npm run coverage

Coverage should be generated into coverage/lcov-report/index.html.

Changes

Version 1.0.0 - 31/07/2015

  • Initial release

Version 1.0.1 - 31/07/2015

Version 1.0.2 - 31/07/2015

Version 1.0.3 - 01/08/2015

Version 1.0.4 - 08/08/2015

  • Transport error events are not propagated to an error event in the Syslog client

Version 1.0.5 - 22/10/2015

  • Redundant release

Version 1.0.6 - 22/10/2015

  • Slight formatting error in the README.md file

Version 1.0.7 - 08/02/2016

  • Remove debug console.dir() statement accidently left in code

Version 1.0.8 - 26/08/2016

  • Variable key in _expandConstantObject() missing var declaration

Version 1.0.9 - 27/10/2016

  • Added mocha test framework
  • Added istanbul test coverage
  • Added tests for aprox 89% coverage
  • Fixed bug where transports where not being reused
  • Fixed bug where some connections would not close()
  • Made options in .log() optional as per existing documentation
  • Make cb in .log() optional and update documentation
  • Fixed bug where error event and .log callback wouldn't predictably receive error
  • close event is now always fired when .close() is called, regarless of open connection
  • New maintainer Paul Grove
  • Updated License
  • Travis-CI and codeclimate build automation and badges
  • Code linted using eslint

Version 1.0.10 - 27/10/2016

  • No changes, issues with publishing to npm

Version 1.0.11 - 14/11/2016

  • Fix miscalculation of PRI for Emegency and Kernel Facitilty/Severity

Version 1.1.0 - 18/05/2017

  • Fix issue resolving IP class from hostname
  • Call log callback asynchronously, preventing issues when closing in that callback
  • Support for RFC 5424
  • Fix erroneous space after PRI

Additional Contributors

  • SirWumpus (github)
  • acanimal (github)
  • cdscott (github)
  • mccarthy (github)
  • MarkHerhold (github)
  • JeremyBernier (github)

License

Copyright (c) 2017 Paul Grove

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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