index.js

var _http = require('http');
var _https = require('https');
var _os = require('os');
var _param = require('./param.json');
var _request = require('request');
var _tools = require('graphdat-plugin-tools');

// remember the previous poll data so we can provide proper counts
var _previous = {};

// if we have a name and password, then add an auth header
var _httpOptions = {};
if (_param.username)
    _httpOptions = { auth: { user: _param.username, pass: _param.password, sendImmediately: true }};

// if we should ignore self signed certificates
if ('strictSSL' in _param && _param.strictSSL === false)
    _httpOptions.strictSSL = false;

// if we do not have a source, then set it
_param.source = _param.source || _os.hostname();

// accumulate a value and return the difference from the previous value
function accumulate(key, newValue)
{
    var oldValue;
    if (key in _previous)
        oldValue = _previous[key];
    else
        oldValue = newValue;

    var difference = diff(newValue, oldValue);
    _previous[key] = newValue;
    return difference;
}

// get the natural difference between a and b
function diff(a, b)
{
    if (a == null || b == null)
        return 0;
    else
        return Math.max(a - b, 0);
}

// validate the input, return 0 if its not an integer
function parse(x)
{
    if (x == null) return 0;

    var y = parseInt(x, 10);
    return (isNaN(y) ? 0 : y);
}

function parseStatsJson(body)
{
    // See http://nginx.org/en/docs/http/ngx_http_status_module.html for body format

    var data;
    try
    {
        data = JSON.parse(body);
    }
    catch(e)
    {
        data = null;
    }

    return data;
}

function parseStatsText(body)
{
    /*
    See http://nginx.org/en/docs/http/ngx_http_stub_status_module.html for body format.
    Sample response:

    Active connections: 1
    server accepts handled requests
     112 112 121
    Reading: 0 Writing: 1 Waiting: 0
     */
    var stats = {};
    body.split('\n').forEach(function(line)
    {
        if (line.indexOf('Active connections:') === 0)
        {
            var active = line.match(/(\w+):\s*(\d+)/);
            stats[active[1].toLowerCase()] = parse(active[2]);
        }
        else if (line.match(/\s*(\d+)\s+(\d+)\s+(\d+)\s*$/))
        {
            var match = line.match(/\s*(\d+)\s+(\d+)\s+(\d+)\s*$/);
            stats.accepts = parse(match[1]);
            stats.handled = parse(match[2]);
            stats.requests = parse(match[3]);
            stats.nothandled = stats.accepts - stats.handled;
        }
        else if (line.match(/(\w+):\s*(\d+)/))
        {
            while(true)
            {
                var kvp = line.match(/(\w+):\s*(\d+)/);
                if (!kvp)
                    break;

                stats[kvp[1].toLowerCase()] = parse(kvp[2]);
                line = line.replace(kvp[0], '');
            }
        }
    });
    return stats;
}

function printEnterpriseStats(stats, cb)
{
    var handled = stats['connections']['accepted'] - stats['connections']['dropped'];
    var requests = stats['requests']['total'];
    var requestsPerConnection = (requests > 0 && handled !== 0) ? requests/handled : 0;

    console.log('NGINX_ACTIVE_CONNECTIONS %d %s', stats['connections']['active'] + stats['connections']['idle'], _param.source);
    console.log('NGINX_WAITING %d %s', stats['connections']['idle'], _param.source);
    console.log('NGINX_HANDLED %d %s', accumulate('NGINX_HANDLED', handled), _param.source);
    console.log('NGINX_NOT_HANDLED %d %s', stats['connections']['dropped'], _param.source);
    console.log('NGINX_REQUESTS %d %s', accumulate('NGINX_REQUESTS', requests), _param.source);
    console.log('NGINX_REQUESTS_PER_CONNECTION %d %s', requestsPerConnection, _param.source);

    // enterprise customers have 'per zone' statistics
    for (var zone_name in stats.server_zones)
    {
        var zone = stats.server_zones[zone_name];
        var src = _param.source + '_' + zone_name;
        console.log('NGINX_REQUESTS %d %s', accumulate('NGINX_REQUESTS_' + zone_name, zone['requests']), src);
        console.log('NGINX_RESPONSES %d %s', accumulate('NGINX_RESPONSES_' + zone_name, zone['responses']['total']), src);
        console.log('NGINX_TRAFFIC_SENT %d %s', accumulate('NGINX_TRAFFIC_SENT_' + zone_name, zone['sent']), src);
        console.log('NGINX_TRAFFIC_RECEIVED %d %s', accumulate('NGINX_TRAFFIC_RECEIVED_' + zone_name, zone['received']), src);
    }

    return cb();
}

function printCommunityStats(stats, cb)
{
    var handled = ('handled' in _previous) ? diff(stats.handled, _previous.handled) : 0;
    var requests = ('requests' in _previous) ? diff(stats.requests, _previous.requests) : 0;
    var requestsPerConnection = (requests > 0 && handled !== 0) ? requests / handled : 0;

    // save the stats so we can calculate differences
    _previous = stats;

    // Report
    console.log('NGINX_ACTIVE_CONNECTIONS %d %s', stats.connections, _param.source);
    console.log('NGINX_READING %d %s', stats.reading, _param.source);
    console.log('NGINX_WRITING %d %s', stats.writing, _param.source);
    console.log('NGINX_WAITING %d %s', stats.waiting, _param.source);
    console.log('NGINX_HANDLED %d %s', handled, _param.source);
    console.log('NGINX_NOT_HANDLED %d %s', stats.nothandled, _param.source);
    console.log('NGINX_REQUESTS %d %s', requests, _param.source);
    console.log('NGINX_REQUESTS_PER_CONNECTION %d %s', requestsPerConnection, _param.source);

    return cb();
}

// call nginx and parse the stats
function getStats(cb)
{
    // call nginx to get the stats page
    _request.get(_param.url, _httpOptions, function(err, resp, body)
    {
        if (err)
            return cb(err);
        if (resp.statusCode === 401)
            return cb(new Error('Nginx returned with an error - recheck the username/password you provided'));
        if (resp.statusCode !== 200)
            return cb(new Error('Nginx returned with an error - recheck the URL you provided'));
        if (!body)
            return cb(new Error('Nginx statistics return empty'));

        var isCommunityEdition;
        var stats;

        if (resp.headers['content-type'] == 'application/json')
        {
            isCommunityEdition = false;
            stats = parseStatsJson(body);
        }
        else
        {
            isCommunityEdition = true;
            stats = parseStatsText(body);
        }

        return cb(null, isCommunityEdition, stats);
    });
}

function finish(err)
{
    if (err)
        console.error(err);

    setTimeout(poll, _param.pollInterval);
}

// get the stats, format the output and send to stdout
function poll(cb)
{
    getStats(function(err, isCommunityEdition, stats)
    {
        if (err)
            return finish(err);
        if (!stats)
            return finish('Could not parse Nginx analytics');

        if (isCommunityEdition)
            printCommunityStats(stats, finish);
        else
            printEnterpriseStats(stats, finish);
    });
}

poll();