Example Nagios plugin using Node.js

check_stuff.js

#!/usr/bin/env node 
/* -*- js2 -*- */

/* ************************************************************* */
// Set up classes to support Range objects. Ported from
// Nagios::Plugin::Range. See named functions below.
// TODO: Modularize properly/idiomatically.

/*
 * Represents a Nagios plugin range object.
 * @constructor
 */
function Range(start, end, alert_on_outside) {
    this.start = start;
    this.end = end;
    this.alert_on_outside = alert_on_outside;
}

Range.prototype = {
    toString: RangeToString,
    check: RangeCheck
};
/* ************************************************************* */




var plugin_name = 'CHECK_STUFF';

// Set up command line args and usage etc using commander.js.
var cli = require('commander');

cli
  .version('0.0.1')
    .option('-c, --critical <critical threshold>', 'Critical threshold using standard format', parseRangeString)
    .option('-w, --warning <warning threshold>', 'Warning threshold using standard format', parseRangeString)
    .option('-r, --result <Number4>', 'Use supplied value, not random', parseFloat)
  .parse(process.argv);


var val = cli.result;
if (val == undefined) {
    val = Math.floor((Math.random() * 20) + 1);
}
var message = ' Sample result was ' + val.toString();

var perfdata = "'Val'="+val + ';' + cli.warning + ';' + cli.critical + ';';

if (cli.critical && cli.critical.check(val)) {
    nagios_exit(plugin_name, "CRITICAL", message, perfdata);
}
else if (cli.warning && cli.warning.check(val)) {
    nagios_exit(plugin_name, "WARNING", message, perfdata);
}
else {
    nagios_exit(plugin_name, "OK", message, perfdata);
}






/* ************************************************************* */

/*
 * Standard stringification a la
 * http://nagiosplug.sourceforge.net/developer-guidelines.html#THRESHOLDFORMAT
 * 
 * E.g. @10:~ means "outside the range 10 to Infinity"
 */
function RangeToString() {
    return ( this.alert_on_outside ? '' : '') + 
	(this.start == Number.NEGATIVE_INFINITY ? '~' : this.start) + 
	':' +
	(this.end == Infinity ? '' : this.end) ;
};

/* 
 * Returns true if an alert should be raised (the value is outside
 * of the range).a
 * 
 * @param v Number  The value to be checked. 
 * @return boolean
 */

function RangeCheck (v) {
    var alerty = false || ! this.alert_on_outside;
    
    if (this.start <= v && v <= this.end) {
	return alerty;
    }
    else {
	return ! alerty;
    }
}


/*
 * See
 * http://nagiosplug.sourceforge.net/developer-guidelines.html#THRESHOLDFORMAT
 * 
 * @param t String The string with a range definition.
 */
function parseRangeString(t) {
    var start = 0;
    var end = Number.POSITIVE_INFINITY;
    var alert_on_outside = true;
    var valid = false;

//    console.log('parsing Range %j', t);

    // Strip whitespace.
    t = t.toString().replace(/\s/g, '');

    // Validate
    if ( ! /[\d~]/.test(t) ||
	 ! /^\@?(-?[\d.]+|~)?(:(-?[\d.]+)?)?$/.test(t)
       ) {
	   console.error('Invalid range definition %j', t);
	   process.exit(3);
       }

    if ( /^@/.test(t)  ) {  
	alert_on_outside = false;
	t = t.substring(1);
    }    

    if ( /^~:/.test(t)  ) {  // '~:x'
	start = Number.NEGATIVE_INFINITY;
	t = t.substring(2);
	valid = true;
    }

    var m = t.match(/^([\d\.-]+)?:/); // '10:'
    if (m != null ) {    
	start = m[1];
	t = t.replace(/^([-\d\.]+)?:/, '');
	valid = true;
    }

    m = t.match(/^([-\d\.]+)$/); // 'x:10' or '10'
    if (m != null ) {    
	end = m[1];
	valid = true;
    }

    if (valid && start <= end) {
	return new Range(start, end, alert_on_outside);
    }
    else {
	console.error('Invalid range definition %j', t);
	process.exit(3);
    }

    return null;
}

// End Range stuff


/*
 * Exit the plugin with Nagios specified output. See
 * http://nagiosplug.sourceforge.net/developer-guidelines.html#PLUGOUTPUT
 * 
 * @param plugin_name String  The name of the plugin e.g. 'CHECK_STUFF'.
 * @param state String  "OK", "WARNING", "CRITICAL" or defaults to "UNKNOWN".
 * @param message String  Human-readable message.
 * @param perfdata String  Nagios formatted perfomance data string.
 */
function nagios_exit (plugin_name, state, message, perfdata) {
    var exit_code, valid_state;

    switch (state.toUpperCase()) {
	case 'CRITICAL':
 	valid_state = state;
	exit_code = 2;
	break;

	case 'WARNING':
 	valid_state = state;
	exit_code = 1;
	break;

	case 'OK':
 	valid_state = state;
	exit_code = 0;
	break;

	default:
 	valid_state = 'UNKNOWN';
	exit_code = 3;
    }

    console.log(plugin_name + ' ' + valid_state + ':' + message + '|' + perfdata);
    process.exit(exit_code);
}