node_helper.js

var NodeHelper = require("node_helper")
var fs = require('fs')
var snmp = require('net-snmp')

var community = null
var host = null
var index = null

var options = {
    port: 161,
    retries: 1,
    timeout: 5000,
    transport: "udp4",
    trapPort: 162,
    version: snmp.Version2c,
    idBitsSize: 16
}

var oid2mib = {
    '1.3.6.1.2.1.2.2.1.2': 'ifDescr',
    '1.3.6.1.2.1.2.2.1.7': 'ifAdminStatus',
    '1.3.6.1.2.1.2.2.1.8': 'ifOperStatus',
    '1.3.6.1.2.1.31.1.1.1.1': 'ifName',
    '1.3.6.1.2.1.31.1.1.1.15': 'ifHighSpeed',
    '1.3.6.1.2.1.31.1.1.1.18': 'ifAlias',

    '1.3.6.1.2.1.31.1.1.1.6': 'ifHCInOctets',
    '1.3.6.1.2.1.31.1.1.1.10': 'ifHCOutOctets',

    '1.3.6.1.2.1.31.1.1.1.7': 'ifHCInUcastPkts',
    '1.3.6.1.2.1.31.1.1.1.11': 'ifHCOutUcastPkts',

    '1.3.6.1.2.1.31.1.1.1.8': 'ifHCInMulticastPkts',
    '1.3.6.1.2.1.31.1.1.1.12': 'ifHCOutMulticastPkts',

    '1.3.6.1.2.1.31.1.1.1.9': 'ifHCInBroadcastPkts',
    '1.3.6.1.2.1.31.1.1.1.13': 'ifHCOutBroadcastPkts',

    '1.3.6.1.2.1.2.2.1.13': 'ifInDiscards',
    '1.3.6.1.2.1.2.2.1.19': 'ifOutDiscards',

    '1.3.6.1.2.1.2.2.1.14': 'ifInErrors',
    '1.3.6.1.2.1.2.2.1.20': 'ifOutErrors'
}

var config = {}
var snmpData = {}

var session = null

var maxRepetitions = 20
var poolerThreadCount = 0
var isPoolerRunning = false
var interval = 0

module.exports = NodeHelper.create({
    start: function() {
        console.log(this.name + ' helper started ...')
    },
    socketNotificationReceived: function(notification, payload) {
        if (notification == "SNMP_POOL_SERVERS") {
            ConfigureSnmp(payload.config)
            if (!isPoolerRunning) { SnmpWalk(this) }
        }
    }
})

function ConfigureSnmp(config) {
    host = config.host
    community = config.community
    if (config.version == 1) {
        options.version = snmp.Version1
    } else {
        options.version = snmp.Version2c
    }
    index = config.index
    interval = config.interval
}

/**
 * Calculates a rate difference between two values
 *
 * @param {integer} latest the latest recived value
 * @param {integer} previous the previous received value
 * @param {integer} timeElapsed the time difference in seconds between both values
 * @return {integer} a value with a rate between both value
 */
function GetSpeed(latest, previous, timeElapsed) {
    var x = (latest - previous) / timeElapsed
    x = Math.round(x, 2)
    return x * 8
}

/**
 * Reads the last saved data, if possible, and compares it against the latest
 * pooled data, returning the download and upload differece between the two pools
 *
 * @return {object} an object with the download and upload data
 */
function PrepareData() {
    var dataPath = __dirname + "/data"
    var dataFile = dataPath + "/snmp.json"
    var live = snmpData
    var liveData = snmpData[host][index]

    // Load previous pooled data and replace with the updated data
    if (fs.existsSync(dataFile)) {
        savedJson = JSON.parse(fs.readFileSync(dataFile, 'utf8'))
        if (!savedJson.hasOwnProperty(host)) {
            // If the IP/name of the host changed then reinitialize
            savedJson[host] = []
            savedJson[host][index] = 0
        }
    } else {
        savedJson = []
        savedJson[host] = []
        savedJson[host][index] = 0
    }

    // Return 0's if there was no previous data, or the speeds would make no sense
    if (typeof savedJson[host] === 'undefined') { return { download: 0, upload: 0 } }
    savedData = savedJson[host][index]

    if ((liveData.timestamp - savedData.timestamp) / 1000 <= interval) {
        return { download: savedData.lastbw.inBits, upload: savedData.lastbw.outBits, highSpeed: savedData.lastbw.ifspeed }
    }

    // Calculates download and upload speeds based on difference between pools
    if (typeof liveData.timestamp !== 'undefined' || typeof savedData.timestamp !== 'undefined') {
        timeDelta = ((liveData.timestamp - savedData.timestamp) / 1000)
        inBits = GetSpeed(liveData.ifHCInOctets, savedData.ifHCInOctets, timeDelta)
        outBits = GetSpeed(liveData.ifHCOutOctets, savedData.ifHCOutOctets, timeDelta)
            // console.log("out: " + outBits + "\tin: " +  inBits + "\tdelta: "+timeDelta + "\tliveTimestamp: " + liveData.timestamp + "\tsavedTimeStamp: " + savedData.timestamp)
    }

    snmpData[host][index]["lastbw"] = {}
    snmpData[host][index]["lastbw"]["inBits"] = inBits
    snmpData[host][index]["lastbw"]["outBits"] = outBits
    snmpData[host][index]["lastbw"]["ifspeed"] = liveData.ifHighSpeed * 1024000

    if (!fs.existsSync(dataPath)) { fs.mkdirSync(dataPath) }
    fs.writeFileSync(dataFile, JSON.stringify(snmpData), 'utf8')

    return { download: inBits, upload: outBits, highSpeed: liveData.ifHighSpeed * 1024000 }
}

/**
 * Walks through an array of OIDs
 *
 * @param  {object} obj the nodeJs object from the main application
 * @return {void}
 */
function SnmpWalk(obj) {
    // Create a session to pool data from the server and regirster two
    // events if there are any errors and when the session/socket is closed
    session = snmp.createSession(host, community, options)
    session.on("error", function(error) {
        console.log(error.toString())
        session.close()
    })
    session.on("close", function(error) {
        isPoolerRunning = false
        obj.sendSocketNotification("SNMP_POOL_RESPONSE", PrepareData())
    })

    //  Walks through all the OID trees in the oids array
    var oids = (Object.keys(oid2mib)).length
        // poolerThreadCount = oids
    isPoolerRunning = true
    for (i = 0; i < oids; i++) {
        poolerThreadCount++
        session.subtree((Object.keys(oid2mib))[i], maxRepetitions, feedCb, doneCb)
    }
}

/**
 * Reports any error messages with the session and closes it.
 * this is triggered when when the session.subtree has completed
 * pooling the SNMP tree
 *
 * @param {object} error An object with the error information
 * @return {void} nothing
 */
function doneCb(error) {
    if (error) console.log(error)
    poolerThreadCount--
    if (poolerThreadCount == 0) {
        isPoolerRunning = false
        session.close()
    }
}

/**
 * Called after net-snmp received data from the server
 *
 * @param {object} res an object with the results of 'walking' the SNMP tree
 * @return {void}
 */
function feedCb(res) {
    for (i = 0; i < res.length; i++) {
        var oidArray = res[i].oid.split('.')
        var idx = oidArray.pop()
        var oid = oidArray.join('.')

        // Add a space in the array for the host if it doesn't exists already
        if (typeof(snmpData[host]) === 'undefined') snmpData[host] = {}

        // As per NET-SNMP documentation, check if there are any errors
        if (snmp.isVarbindError(res[i])) console.error(snmp.varbindError(res[i]))

        // Add the interface index to the SNMP data array
        if (typeof(snmpData[host][idx]) === 'undefined') snmpData[host][idx] = {}

        // Add a timestamp record to the SNMP data array and store the pooled
        // SNMP value, and convert the OID to it friendly name
        snmpData[host][idx]['timestamp'] = +new Date()
        snmpData[host][idx][oid2mib[oid]] = ConvertBuffer(res[i]) //.toString()
    }
}

/**
 * Converts a buffer to human readable getNext
 * TODO: This requires a better implementation
 *
 * @param  {object} snmpObj an object from a snmp query
 * @return {void}
 */
function ConvertBuffer(snmpObj) {
    if (snmpObj.type == 4) { return snmpObj.value.toString() }
    if (snmpObj.type == 2) { return snmpObj.value }
    if (snmpObj.type == 62) { return snmpObj.value }
    if (snmpObj.type == 65) { return snmpObj.value }
    if (snmpObj.type == 66) { return snmpObj.value }
    if (snmpObj.type == 70) {
        var buf = new Buffer.alloc(4)
        buf.write(snmpObj.value.toString(), 0)
        return parseInt(snmpObj.value.toString('hex'), 16)
    }
}