<glacius:metadata>

    <title>Writing to the syslog with Winston</title>

    <description>NodeJS logging with Winston and syslog</description>

    <category>Legacy blog posts</category>

    <category>Programming</category>

    <category>JavaScript</category>

    <category>Node.js</category>

</glacius:metadata>

<glacius:macro name="legacy blargh banner">

    <properties>

        <originalUrl>https://tmont.com/blargh/2013/12/writing-to-the-syslog-with-winston</originalUrl>

        <originalDate>2013-12-24T04:05:46.000Z</originalDate>

    </properties>

</glacius:macro>

<p>

  <strong>Update:</strong> this code is now in its own 

  <a href="https://github.com/tmont/winston-syslog">GitHub repository</a>.

</p>

<hr />

<p>

  Many log aggregators (such as <a href="https://papertrailapp.com/">Papertrail</a> 

  or <a href="https://www.loggly.com/">Loggly</a>) have the ability to parse data from the

  syslog. This is often more convenient than writing to a file, handling

  rotation of said log file, handling archival of said rotated log file, and a 

  myriad of other annoyances. Plus, many other system programs (ssh, cron, etc.)

  already log stuff to the syslog, so most things are already aggregated.

</p>

<p>

  I use <a href="https://github.com/flatiron/winston">Winston</a> as my logging library

  for Node. It works pretty well inasmuch as it lets you log stuff. Winston exposes a

  <code>Transport</code> object, which is an interface to a logging destination (a file,

  the console, a webhook, etc.). You can use this to log to the syslog.

</p>

<p>

  Note that there are other modules for Winston that expose a syslog transport, but

  they all made me nervous, in that they weren't tested, and after glancing through

  the code, I wasn't convinced they were doing proper socket management. And the last

  thing I wanted was my logging library to create hundreds of undisposed file descriptors.

  So I decided to use <a href="https://github.com/melor/node-posix">node-posix</a> and just

  use the OS to write to the syslog rather than UDP. Plus <code>syslogd</code> doesn't

  have datagram support enabled by default, so you need to tweak the configuration to make

  it accept UDP packets, and I don't know enough about syslog to feel confident in messing

  with the configuration. And also I didn't feel like spending an hour learning about it.

  Because I'm weak and stupid.

</p>

<p>

  Anyway, here's some sample code to write to the syslog using the OS's POSIX functions.

</p>

<glacius:code lang="javascript"><![CDATA[

var winston = require('winston'),

	util = require('util'),

	posix = require('posix');

function SyslogTransport(options) {

	options = options || {};

	winston.Transport.call(this, options);

	this.id = options.id || process.title;

	this.facility = options.facility || 'local0';

	this.showPid = !!options.showPid;

}

util.inherits(SyslogTransport, winston.Transport);

util._extend(SyslogTransport.prototype, {

	name: 'syslog',

	log: function(level, msg, meta, callback) {

		if (this.silent) {

			callback(null, true);

			return;

		}

		if (level === 'error') {

			level = 'err';

		} else if (level === 'warn') {

			level = 'warning';

		}

		var message = '[' + level + '] ' + msg;

		if (typeof(meta) === 'string') {

			message += ' ' + meta;

		} else if (meta && typeof(meta) === 'object' && Object.keys(meta).length > 0) {

			message += ' ' + util.inspect(meta, false, null, false);

		}

		message = message.replace(/\u001b\[(\d+(;\d+)*)?m/g, '');

		var options = {

			cons: true,

			pid: this.showPid

		};

		posix.openlog(this.id, options, this.facility);

		posix.syslog(level, message);

		posix.closelog();

		callback(null, true);

	}

});

module.exports = SyslogTransport;

]]></glacius:code>

<p>

  And you could use it like so:

</p>

<glacius:code lang="javascript"><![CDATA[

var transport = new SyslogTransport({

	level: 'debug',

	id: 'hello syslog',

	facility: 'user',

	showPid: true

});

var log = new winston.Logger({

	level: 'debug',

	transports: [ transport ]

});

log.info('hello world');

]]></glacius:code>

<p>

  And then if you run <code>tail /var/log/syslog</code> (<code>/var/log/messages</code> 

  on OS X, I think), you should see something like this:

</p>

<glacius:code lang="plaintext"><![CDATA[

Dec 23 12:01:50 mesia hello syslog[17605]: [info] hello world

]]></glacius:code>