monitor-assign.go

package main

import (
	"flag"
	"fmt"
	"math"
	"math/rand"
	"os"
	"os/signal"
	"strconv"
	"time"

	"uc-monitor-go-test/cnml"
	"uc-monitor-go-test/goclidote"

	"github.com/golang/glog"
)

var dbHost = "localhost"
var dbHostHelp = "The hostname or IP address where AntidoteDB is running"
var dbPort = 8087
var dbPortHelp = "The TCP port on which AntidoteDB is listening"

// The Timestamps struct contains a monitor's timestamp and a local timestamp
type Timestamps struct {
	monitor int64
	local   int64
}

// The MonitorTimestamp struct contains a monitor's id and timestamps
type MonitorTimestamp struct {
	id         string
	timestamps Timestamps
}

// Error levels

// FATAL output code
var FATAL = 1

// ERROR output code
var ERROR = 2

// WARNING output code
var WARNING = 3

// INFO output code
var INFO = 4

// DEFAULTFILEMODE for created files
var DEFAULTFILEMODE os.FileMode = 0755

//Default settings and descriptions

// monitorTimeout defines how long to wait before removing a crashed monitor from the database
var monitorTimeout int64 = 450
var monitorTimeoutHelp = "Time before deregistering crashed monitors or in network partition"

// idNum holds the monitor id, in numberic form
var idNum int

// ID represents the ID of the monitor, in alfanumeric form
var ID = "0"
var idHelp = "Numeric ID of this monitoring instance"

// IDts holds a timestamp
var IDts = "0_ts"

// minMons defines the minimum number of monitors a deviced must be assigned to
// so that it is considered to have enough redundancy
var minMons = 3
var minMonsHelp = "Minimum number of monitors to assign to each device"

// maxMons defines the maximum number of monitors a device must be assigned to,
// so that it is not monitored by more monitors than needed
var maxMons = minMons + 1
var maxMonsHelp = "Maximum number of monitors to assign to each device"

// maxDevs defines the default maximum number of nodes a monitor is assigned to
var maxDevs = 1000
var maxDevsHelp = "Maximum number of devices to monitor"

var devsCheckInterval = 150
var devsCheckIntervalHelp = "Interval (in seconds) in which to check for changes in the devices list"

var fillingTime = 150
var fillingTimeHelp = "Interval (in seconds) for filling the local assignation list"

var reassignInterval = 150
var reassignIntervalHelp = "Interval (in seconds) in which to update the local devices assignation list"

var globalAssignCheckInterval = 150
var globalAssignCheckIntervalHelp = "Interval (in seconds) in which to check for changes in the global devices assignation list"

var policy = 1
var policyHelp = "Network devices to monitoring servers assignation policy"

// Global data structures
var cnmlDevices []cnml.DeviceIpv4sGraphserver    //The global list with all the fetched devices and their IPv4 addresses
var cnmlDevicesChecksum string                   //The checksum of the last global devices list and IPv4 addresses fetched
var localAssign []cnml.DeviceMonitorAssignation  //The list of locally assigned devices and their IPv4 addresses
var globalAssign []cnml.DeviceMonitorAssignation //The global assignation list of devices<=>monitors
var globalTimestamps []MonitorTimestamp

func main() {
	//Initialize the service (read the configuration flags, etc.)
	initialize()

	// Handle interrupt signals in order to terminate gracefully
	signalChan := make(chan os.Signal, 1)
	cleanupDone := make(chan bool)
	signal.Notify(signalChan, os.Interrupt)
	go func() {
		for _ = range signalChan {
			fmt.Println("\nReceived an interrupt, deregistering from the monitors list and quitting...")

			deregisterMonitorInAntidote(ID)
			cleanupDone <- true
		}
	}()
	<-cleanupDone
	fmt.Println("\nBye!")
}

// The initialize() function manages the execution parameters, sets timers, etc.
func initialize() {

	fmt.Println("Initializing...")

	// Manage command line flags and execution settings
	initializeFlags()

	// Register as a monitor to Antidote's list of active Monitors
	registerMonitorInAntidote()

	// Publish the maxDev value for this monitor
	updateMonitorMaxDevsInAntidote()

	// Initialize periodic timers
	initializeTimers()

	// The application is now initialized; entering the loop
	fmt.Println("Initialization done. Entering infinite loop...")
}

func initializeTimers() {
	// Initialize cnmlDevices checksum changes check timer
	startcnmlDevicesChecksumTimer()

	// Initialize cnmlDevices checksum changes check timer
	startAssignTimer()
}

// The initializeFlags function initializes the command line flags
func initializeFlags() {

	//Define and parse command line flags
	dbHostPtr := flag.String("db_host", dbHost, dbHostHelp)
	dbPortPtr := flag.Int("db_port", dbPort, dbPortHelp)
	idInt, _ := strconv.ParseInt(ID, 10, 32)
	idPtr := flag.Int("id", int(idInt), idHelp)
	minMonsPtr := flag.Int("minMons", minMons, minMonsHelp)
	maxMonsPtr := flag.Int("maxMons", maxMons, maxMonsHelp)
	maxDevsPtr := flag.Int("maxDevs", maxDevs, maxDevsHelp)
	devsCheckIntervalPtr := flag.Int("devsCheckInterval", devsCheckInterval, devsCheckIntervalHelp)
	fillingTimePtr := flag.Int("fillingTime", fillingTime, fillingTimeHelp)
	reassignIntervalPtr := flag.Int("reassignInterval", reassignInterval, reassignIntervalHelp)
	globalAssignCheckIntervalPtr := flag.Int("globalAssignCheckInterval", globalAssignCheckInterval, globalAssignCheckIntervalHelp)
	monitorTimeoutPtr := flag.Int("monitorTimeout", int(monitorTimeout), monitorTimeoutHelp)
	policyPtr := flag.Int("policy", int(policy), policyHelp)

	flag.Parse()

	//Service id
	if *idPtr > 0 {
		idNum = *idPtr
		ID = fmt.Sprint(*idPtr)
		IDts = fmt.Sprintf("%s_ts", ID)
		fmt.Println("Using ID", ID)
	} else {
		randsource := rand.New(rand.NewSource(time.Now().UnixNano()))
		ID = fmt.Sprint("a", 100000+randsource.Intn(900000))
		fmt.Println("Using anonymous id", ID)
		IDts = fmt.Sprintf("%s_ts", ID)
	}

	dbHost = *dbHostPtr
	dbPort = *dbPortPtr

	//Maximum devices to monitor
	if *maxDevsPtr > 0 {
		maxDevs = *maxDevsPtr
	}

	// Minimum and maximum monitors per device
	if *minMonsPtr > 0 {
		minMons = *minMonsPtr
	}
	if *maxMonsPtr >= minMons {
		maxMons = *maxMonsPtr
	}

	//Timers for tickers (intervals)
	if *devsCheckIntervalPtr > 0 {
		devsCheckInterval = *devsCheckIntervalPtr
	}
	if *fillingTimePtr > 0 {
		fillingTime = *fillingTimePtr
	}
	if *reassignIntervalPtr > 0 {
		reassignInterval = *reassignIntervalPtr
	}
	if *globalAssignCheckIntervalPtr > 0 {
		globalAssignCheckInterval = *globalAssignCheckIntervalPtr
	}
	if *monitorTimeoutPtr > 0 {
		monitorTimeout = int64(*monitorTimeoutPtr)
	}
	if monitorTimeout <= int64(globalAssignCheckInterval) || monitorTimeout <= int64(reassignInterval) {
		monitorTimeout = int64(math.Max(float64(globalAssignCheckInterval), float64(reassignInterval))) + 1
	}

	//Policy
	if *policyPtr >= 1 && *policyPtr <= 2 {
		policy = *policyPtr
	}
}

// Get the global devices list from AntidoteDB
func getCnmlDevicesList() []cnml.DeviceIpv4sGraphserver {
	return goclidote.ReadDevicesFromAntidote(dbHost, dbPort)
}

// Update globalAssign from the current shared database status
func updateGlobalAssignationList() {
	fmt.Println("Updating globalAssign...")

	var newDevices []cnml.DeviceMonitorAssignation
	var currDevices []cnml.DeviceMonitorAssignation
	var oldDevices []cnml.DeviceMonitorAssignation

	// Iterate through all the devices known to the monitoring system
	for _, v := range cnmlDevices {
		if isDeviceInAssignationSlice(v.ID, globalAssign) {
			// We already know this device; update its monitors assignation from AntidoteDB
			globalAssign[posDeviceInAssignationSlice(v.ID, globalAssign)].MonitorID = goclidote.AntidoteReadItemsFromSetInBucket(fmt.Sprintf("device-%d", v.ID), "monitors", dbHost, dbPort)
		} else {
			// A new device from the cnmlDevices list; add it to a new devices list to append it below
			fmt.Printf("Adding device %d from cnmlDevices into globalAssign\n", v.ID)
			var newDev cnml.DeviceMonitorAssignation
			newDev.Device.ID = v.ID
			newDev.Device.Addresses = v.Addresses
			newDev.MonitorID = goclidote.AntidoteReadItemsFromSetInBucket(fmt.Sprintf("device-%d", v.ID), "monitors", dbHost, dbPort)
			newDevices = append(newDevices, newDev)
		}
	}

	// The globalAssign list may contain old devices, not in the CNML anymore; discard them
	for _, v := range globalAssign {
		if isDeviceInSliceByID(v.Device.ID, cnmlDevices) {
			currDevices = append(currDevices, v)
		} else {
			oldDevices = append(oldDevices, v)
		}
	}

	// Leave in globalAssign only current devices
	globalAssign = currDevices

	// Append the new devices to the globalAssign list
	for _, v := range newDevices {
		globalAssign = append(globalAssign, v)
	}

	fmt.Println("globalAssign updated!")
}

func updateLocalAssignationList() {

	var currlocalAssign []cnml.DeviceMonitorAssignation
	var oldlocalAssign []cnml.DeviceMonitorAssignation

	// The localAssign list may contain old devices, not in the CNML anymore;
	// discard them.
	for _, v := range localAssign {
		if isDeviceInSliceByID(v.Device.ID, cnmlDevices) {
			currlocalAssign = append(currlocalAssign, v)
		} else {
			oldlocalAssign = append(oldlocalAssign, v)
		}
	}

	// TODO: also look for devices in localAssign NOT assigned to this monitor, which should never have happened

	localAssign = currlocalAssign
}

func mergeGlobalAssignIntoLocalAssign() {

	var newlocalAssign []cnml.DeviceMonitorAssignation

	// Search for those devices in the globalAssign list that have this monitor
	// assigned. Check if they are already in the localAssign list, or add them
	// otherwise
	for _, v := range globalAssign {
		for _, w := range v.MonitorID {
			if w == ID {
				var inLocal = false
				for _, x := range localAssign {
					if v.Device.ID == x.Device.ID {
						inLocal = true
						break
					}
				}
				if !inLocal {
					newlocalAssign = append(newlocalAssign, v)
				}
			}
		}
	}

	for _, v := range newlocalAssign {
		localAssign = append(localAssign, v)
	}
}

func manageMonitorsList() {
	fmt.Println("")
	fmt.Println("Managing the monitors list...")

	// Fetch the current monitors list
	currentMonitors := goclidote.AntidoteReadItemsFromSetInBucket("guifi", "monitors", dbHost, dbPort)
	fmt.Println(len(currentMonitors), "monitors registered in the database:")
	var monitors = ""
	for _, v := range currentMonitors {
		if monitors == "" {
			monitors = v
		} else {
			monitors = fmt.Sprintf("%s, %s", monitors, v)
		}
	}
	fmt.Println(monitors)

	// Create an array and store the timestamps fetched from the database
	var currentTimestamps []MonitorTimestamp

	for _, v := range currentMonitors {
		var thisMonitor MonitorTimestamp

		mts, err := strconv.ParseInt(goclidote.AntidoteReadRegisterInBucket("guifi", fmt.Sprintf("%s_ts", v), dbHost, dbPort), 10, 64)
		errCheck(err, WARNING, fmt.Sprintf("Unable to read the timestamp from Antidote for monitor %s", v))

		thisMonitor.id = v
		thisMonitor.timestamps.monitor = mts
		thisMonitor.timestamps.local = time.Now().Unix()

		currentTimestamps = append(currentTimestamps, thisMonitor)
	}

	var nextGlobalTimestamps []MonitorTimestamp

	// Iterate the fetched timestamps list and process it
	for _, v := range currentTimestamps {
		var knownMonitor = false

		// Iterate the local timestamps list
		for _, w := range globalTimestamps {

			// Look for matching IDs in both lists
			if v.id == w.id {
				knownMonitor = true

				// Check if the timestamps are the same (i.e., the monitor has not
				// reported itself to the database recently)
				if v.timestamps.monitor == w.timestamps.monitor {
					// The monitor is not updating its info to the database, check local timestamps
					if v.timestamps.local-w.timestamps.local > monitorTimeout {
						// Deregister the monitor
						fmt.Println("Deregistering crashed monitor", v.id)
						deregisterMonitorInAntidote(v.id)
					} else {
						nextGlobalTimestamps = append(nextGlobalTimestamps, w)
					}
					// The monitor is updating its info to the database, keep the latest info
				} else {
					nextGlobalTimestamps = append(nextGlobalTimestamps, v)
				}
			}
		}

		// This monitor is new, save it for the next iteration
		if knownMonitor == false {
			nextGlobalTimestamps = append(nextGlobalTimestamps, v)
		}
	}

	globalTimestamps = nextGlobalTimestamps
}

// The sanitizeAssignationsInDatabase function gets the current list of monitors
// from the database, the current nodes<->monitors assignations, and sanitizes
// it (unassigns crashed monitors, etc.)
func sanitizeAssignationsInDatabase() {
	fmt.Println("")
	fmt.Println("Sanitizing the assignation list...")

	// TODO: This list of monitors should be the same as the one just asked for
	// in the manageMonitors function. Try to minimize calls by doing it only once

	// Update the current monitors list
	fmt.Println("Getting the current monitors list...")
	currentMonitors := getCurrentMonitorsList()

	// Update the current devices list
	fmt.Println("Updating the current cnml...")
	cnmlDevices = getCnmlDevicesList()

	for _, v := range globalAssign {
		// fmt.Println("############")
		// fmt.Println(k, ": device ID:", v.Device.ID)
		// fmt.Println("Monitors:", v.MonitorID)
		for _, w := range v.MonitorID {
			var monitorFound = false
			for _, x := range currentMonitors {
				if w == x {
					monitorFound = true
					fmt.Println(fmt.Sprintf("Monitor %s found, keeping it for device %d", w, v.Device.ID))
				}
			}
			if monitorFound == false {
				fmt.Println(fmt.Sprintf("Monitor %s not found, unassigning it from device %d", w, v.Device.ID))
				unassignMonitorFromDevice(w, v.Device.ID)
			}
		}
	}
	fmt.Println("Ended assignation list sanitization...")
}

func getCurrentMonitorsList() []string {
	return goclidote.AntidoteReadItemsFromSetInBucket("guifi", "monitors", dbHost, dbPort)
}

func assignMonitorFromDevice(monitorID string, deviceID int) bool {
	return goclidote.AntidoteAddItemToSetInBucket(fmt.Sprintf("device-%d", deviceID), "monitors", monitorID, dbHost, dbPort)
}

func unassignMonitorFromDevice(monitorID string, deviceID int) bool {
	return goclidote.AntidoteRemoveItemFromSetInBucket(fmt.Sprintf("device-%d", deviceID), "monitors", monitorID, dbHost, dbPort)
}

func reassignDevs() {
	fmt.Println("")
	fmt.Println("Reassignation of devices")
	fmt.Println(len(localAssign), "devices currently assigned to this monitor (maximum:", maxDevs, "devices)")

	// Track changes in the assignation list
	assignChange := false

	switch policy {
	case 1:
		// Policy #1: The monitoring server self-assigns those network devices that
		// have less monitoring devices assigned than the minimum number specified
		// by the minMons parameter. Devices are picked randomly until the server
		// reaches its maximum number of monitored devices, specified by the maxDevs
		// parameter.

		// Check if more nodes can be assigned, and if there are any devices not
		// being monitored by this server that could be assigned
		if (len(localAssign) < maxDevs) && (len(localAssign) < len(cnmlDevices)) {

			// Calculate how many new devices can be assigned
			toassign := int(math.Min(float64(int(math.Min(math.Min(float64(len(cnmlDevices)), float64(maxDevs))*float64(devsCheckInterval)/float64(fillingTime)+1, float64(len(cnmlDevices)-len(localAssign))))), float64(maxDevs-len(localAssign))))
			fmt.Println("Assigning up to", toassign, "new devices")

			// Create a list with all the unassigned devices
			var unassignedDevices []cnml.DeviceIpv4sGraphserver
			for _, v := range cnmlDevices {
				if !isDeviceInAssignationSlice(v.ID, localAssign) && (!isDeviceInAssignationSlice(v.ID, globalAssign) || len(globalAssign[posDeviceInAssignationSlice(v.ID, globalAssign)].MonitorID) < minMons) {
					unassignedDevices = append(unassignedDevices, v)
				}
			}
			fmt.Println(len(unassignedDevices), "devices unassigned")

			fmt.Println("Picking", toassign, "devices randomly")

			// Select some devices to self-assign, up to the previously calculated
			// value in the "toassign" variable
			for i := 0; i < toassign; i++ {
				// Check if unassigned devices remain
				if len(unassignedDevices) > 0 {
					// Pick a random device from the unassigned list
					randsource := rand.New(rand.NewSource(time.Now().UnixNano()))
					j := randsource.Intn(len(unassignedDevices))
					// Save it to the new assigned devices list
					var newAssignDev cnml.DeviceMonitorAssignation
					newAssignDev.Device.ID = unassignedDevices[j].ID
					newAssignDev.Device.Addresses = unassignedDevices[j].Addresses
					newAssignDev.MonitorID = append(newAssignDev.MonitorID, ID)
					localAssign = append(localAssign, newAssignDev)
					assignChange = true
					// Remove it from the unassigned devices list
					unassignedDevices = rmDeviceFromSlice(unassignedDevices[j], unassignedDevices)
				} else {
					fmt.Println(toassign-i, "more devices were to be assigned, but no unassigned devices remain")
					break
				}
			}
			fmt.Println(len(localAssign), "devices currently assigned to this monitor")
		} else {
			fmt.Println("Not assigning any new device.")
		}

	case 2:
		// Policy #2: The monitoring server self-assigns those network devices that
		// have the least monitoring devices already assigned. Devices are picked
		// randomly, from those with less monitors, until the server reaches its
		// maximum number of monitored devices specified by the maxDevs parameter.

		// Check if more nodes can be assigned, and if there are any devices not
		// being monitored by this server that could be assigned
		if (len(localAssign) < maxDevs) && (len(localAssign) < len(cnmlDevices)) {

			// Calculate how many new devices can be assigned
			toassign := int(math.Min(float64(int(math.Min(math.Min(float64(len(cnmlDevices)), float64(maxDevs))*float64(devsCheckInterval)/float64(fillingTime)+1, float64(len(cnmlDevices)-len(localAssign))))), float64(maxDevs-len(localAssign))))
			fmt.Println("Assigning up to", toassign, "new devices")

			// Calculate which is the number of least monitors a device has
			leastMons := 0

			var unassignedDevices []cnml.DeviceIpv4sGraphserver

			for leastMons < maxMons && len(unassignedDevices) == 0 {
				for _, v := range cnmlDevices {
					if !isDeviceInAssignationSlice(v.ID, globalAssign) || (!isDeviceInAssignationSlice(v.ID, localAssign) && len(globalAssign[posDeviceInAssignationSlice(v.ID, globalAssign)].MonitorID) < leastMons) {
						unassignedDevices = append(unassignedDevices, v)
					}
				}
				leastMons = leastMons + 1
			}
			fmt.Println(len(unassignedDevices), "devices unassigned")

			fmt.Println("Picking up to", toassign, "devices randomly")

			// Select some devices to self-assign, up to the previously calculated
			// value in the "toassign" variable
			for i := 0; i < toassign; i++ {
				// Check if unassigned devices remain
				if len(unassignedDevices) > 0 {
					// Pick a random device from the unassigned list
					randsource := rand.New(rand.NewSource(time.Now().UnixNano()))
					j := randsource.Intn(len(unassignedDevices))
					// Save it to the new assigned devices list
					var newAssignDev cnml.DeviceMonitorAssignation
					newAssignDev.Device.ID = unassignedDevices[j].ID
					newAssignDev.Device.Addresses = unassignedDevices[j].Addresses
					newAssignDev.MonitorID = append(newAssignDev.MonitorID, ID)
					localAssign = append(localAssign, newAssignDev)
					assignChange = true
					// Remove it from the unassigned devices list
					unassignedDevices = rmDeviceFromSlice(unassignedDevices[j], unassignedDevices)
				} else {
					fmt.Println(toassign-i, "more devices were to be assigned, but no unassigned devices remain")
					break
				}
			}
			fmt.Println(len(localAssign), "devices currently assigned to this monitor")
		} else {
			fmt.Println("Not assigning any new device.")
		}
		fmt.Println("Global average load:", calculateGlobalAverageLoad())
	}

	// Update the new assigned devices to the global shared list
	if assignChange {
		fmt.Println("Exporting the new assigned devices list")
		for _, v := range localAssign {
			goclidote.AntidoteAddItemToSetInBucket(fmt.Sprintf("device-%d", v.Device.ID), "monitors", ID, dbHost, dbPort)
		}
		// localLoad := math.min(1, float64(len(localAssign))/float64(maxDevs))
	}
}

// // Check for devices assigned locally that are no longer in the global devices list
// func checkOutdatedLocalDevices() {
//
// 	assignChange := false                       // Track changes in the assignation list
// 	var deldevs []cnml.DeviceMonitorAssignation // Storage for the deleted devices
// 	newlocalAssign := localAssign               // Duplicate the local list of assigned devices
//
// 	for _, v := range localAssign {
// 		if !isDeviceInSliceByID(v.Device.ID, cnmlDevices) {
// 			fmt.Println("Removing old device ", v.Device.ID, " from the local assigned devices list")
// 			deldevs = append(deldevs, v)
// 			newlocalAssign = rmDeviceFromAssignationList(v.Device.ID, newlocalAssign)
// 			assignChange = true
// 		}
// 	}
//
// 	// Save the new local assigned devices, if changes have been made
// 	if assignChange {
// 		localAssign = newlocalAssign
// 		for _, v := range deldevs {
// 			goclidote.AntidoteRemoveItemFromSetInBucket(fmt.Sprintf("device-%d", v.Device.ID), "monitors", ID, dbHost, dbPort)
// 		}
// 	}
// }

func addDevicesAssignedByGraphserver() {
	for _, v := range cnmlDevices {
		if isDeviceInAssignationSlice(v.ID, localAssign) {
			graphserver := false
			deviceMonitors := globalAssign[posDeviceInAssignationSlice(v.ID, localAssign)].MonitorID

			for _, w := range deviceMonitors {
				if w == ID {
					graphserver = true
					break
				}
			}

			if !graphserver {
				globalAssign[posDeviceInAssignationSlice(v.ID, localAssign)].MonitorID = append(deviceMonitors, ID)
			}
		}
	}
}

func posDeviceInSlice(device cnml.DeviceIpv4sGraphserver, slice []cnml.DeviceIpv4sGraphserver) int {
	for k, v := range slice {
		if device.ID == v.ID {
			return k
		}
	}
	return -1
}

func posDeviceInSliceByID(deviceID int, slice []cnml.DeviceIpv4sGraphserver) int {
	for k, v := range slice {
		if deviceID == v.ID {
			return k
		}
	}
	return -1
}

func isDeviceInSlice(device cnml.DeviceIpv4sGraphserver, slice []cnml.DeviceIpv4sGraphserver) bool {
	if posDeviceInSlice(device, slice) >= 0 {
		return true
	}

	return false
}

func isDeviceInSliceByID(deviceID int, slice []cnml.DeviceIpv4sGraphserver) bool {
	if posDeviceInSliceByID(deviceID, slice) >= 0 {
		return true
	}

	return false
}

func posDeviceInAssignationSlice(device int, slice []cnml.DeviceMonitorAssignation) int {
	for k, v := range slice {
		if device == v.Device.ID {
			return k
		}
	}
	return -1
}

func isDeviceInAssignationSlice(device int, slice []cnml.DeviceMonitorAssignation) bool {
	if (posDeviceInAssignationSlice(device, slice)) >= 0 {
		return true
	}
	return false
}

func posMonitorInSlice(id string, slice []cnml.AssignChecksum) int {
	for k, v := range slice {
		if ID == v.MonitorID {
			return k
		}
	}
	return -1
}

func isMonitorInSlice(id string, slice []cnml.AssignChecksum) bool {
	if posMonitorInSlice(id, slice) >= 0 {
		return true
	}
	return false
}

func rmDeviceFromSlice(device cnml.DeviceIpv4sGraphserver, slice []cnml.DeviceIpv4sGraphserver) []cnml.DeviceIpv4sGraphserver {

	if isDeviceInSlice(device, slice) {
		pos := posDeviceInSlice(device, slice)

		return append(slice[:pos], slice[pos+1:]...)
	}
	return slice
}

func rmDeviceFromAssignationList(DeviceID int, slice []cnml.DeviceMonitorAssignation) []cnml.DeviceMonitorAssignation {

	if isDeviceInAssignationSlice(DeviceID, slice) {
		pos := posDeviceInAssignationSlice(DeviceID, slice)

		return append(slice[:pos], slice[pos+1:]...)
	}
	return slice
}

func startcnmlDevicesChecksumTimer() {
	cnmlDevicesChecksumTicker := time.NewTicker(time.Duration(devsCheckInterval) * time.Second)
	go func() {
		for range cnmlDevicesChecksumTicker.C {
			// TODO: global checksum via AntidoteDB must be implemented in fetch app
			// checkcnmlDevicesChecksum()
		}
	}()
}

func startAssignTimer() {
	localAssignTicker := time.NewTicker(time.Duration(reassignInterval) * time.Second)
	go func() {
		for range localAssignTicker.C {
			// Register this monitor, or update the timestamp
			registerMonitorInAntidote()

			// Update CNML devices list
			cnmlDevices = getCnmlDevicesList()

			// Update the global assignations list from AntidoteDB
			updateGlobalAssignationList()

			// Update the local assignations list to check for outdated devices
			updateLocalAssignationList()

			// Merge globalAssign into localAssign (local = local OR global)
			mergeGlobalAssignIntoLocalAssign()

			// Do the actual reassignation of devices to this monitor
			reassignDevs()

			// Manage the monitors list
			manageMonitorsList()

			// Sanitize the global assignations in the shared database
			sanitizeAssignationsInDatabase()
		}
	}()
}

// Register this monitor in the shared database
func registerMonitorInAntidote() {
	// Update its timestamp
	updateMonitorTimestampInAntidote()

	// Get the current monitors list
	monitors := goclidote.AntidoteReadItemsFromSetInBucket("guifi", "monitors", dbHost, dbPort)

	// If this monitor is already there, return
	for _, v := range monitors {
		if v == ID {
			return
		}
	}

	// Write the monitor to the shared database otherwise
	goclidote.AntidoteAddItemToSetInBucket("guifi", "monitors", ID, dbHost, dbPort)
}

func updateMonitorTimestampInAntidote() {
	timestamp := time.Now().Unix()
	goclidote.AntidoteSetRegisterInBucket("guifi", IDts, fmt.Sprintf("%d", timestamp), dbHost, dbPort)
	fmt.Println("Setting timestamp to", timestamp)
}

func updateMonitorMaxDevsInAntidote() {
	goclidote.AntidoteSetRegisterInBucket("guifi", fmt.Sprintf("%s_maxdevs", ID), fmt.Sprintf("%d", maxDevs), dbHost, dbPort)
	fmt.Println("Setting capacity to", maxDevs)
}

// Deregister a monitor from AntidoteDB (e.g., on exit, or on crash)
func deregisterMonitorInAntidote(monitorID string) {

	// Try up to 3 times
	for i := 0; i < 3; i++ {
		if goclidote.AntidoteRemoveItemFromSetInBucket("guifi", "monitors", monitorID, dbHost, dbPort) {
			fmt.Println("Deregistration successful")
			break
		} else {
			fmt.Println("Deregistration unsuccessful")
		}
	}

	goclidote.AntidoteRemoveRegisterInBucket("guifi", fmt.Sprintf("%s_ts", monitorID), dbHost, dbPort)
}

func calculateGlobalAverageLoad() float64 {

	var monitors = getCurrentMonitorsList()
	var monitorsMaxDevs []int
	var monitorAssignedDevs []int

	for _, v := range monitors {
		capacity, err := strconv.ParseInt(goclidote.AntidoteReadRegisterInBucket("guifi", fmt.Sprintf("%s_maxdevs", v), dbHost, dbPort), 10, 64)
		errCheck(err, WARNING, fmt.Sprintf("Monitor %s has an invalid maxDev", v))

		if err == nil && capacity > 0 {
			monitorsMaxDevs = append(monitorsMaxDevs, int(capacity))
		} else {
			monitorsMaxDevs = append(monitorsMaxDevs, 0)
		}
		monitorAssignedDevs = append(monitorAssignedDevs, 0)
	}

	fmt.Println("len(globalAssign):", len(globalAssign))
	for _, v := range globalAssign {
		fmt.Println(v)
		for _, w := range v.MonitorID {
			fmt.Println("len(monitors):", len(monitors))
			for m, x := range monitors {
				if w == x {
					monitorAssignedDevs[m] = monitorAssignedDevs[m] + 1
				}
			}
		}
	}

	var globalMaxDevs uint64
	var globalAssignedDevs uint64

	for _, v := range monitorsMaxDevs {
		globalMaxDevs = globalMaxDevs + uint64(v)
	}
	for _, v := range monitorAssignedDevs {
		globalAssignedDevs = globalAssignedDevs + uint64(v)
	}

	fmt.Println(monitors)
	fmt.Println(monitorsMaxDevs)
	fmt.Println(monitorAssignedDevs)

	if globalMaxDevs > 0 {
		if globalAssignedDevs >= 0 {
			if globalAssignedDevs <= globalMaxDevs {
				// Standard case
				return float64(globalAssignedDevs) / float64(globalMaxDevs)
			}
			// Overload case, or monitors not reporting properly maxDevs
			return 1

		}
		// Weird case with negative assigned devices
		return 0
	}
	// Corner case when no monitors are registered, or not reporting properly;
	// return a compromise 50% load
	return 0.5
}

func errCheck(e error, level int, message string) {

	if message == "" {
		message = "Unknown error"
	}
	if e != nil {
		switch level {
		case FATAL:
			glog.Fatalln(message, e)
		case ERROR:
			glog.Errorln(message, e)
		case WARNING:
			glog.Warningln(message, e)
		default:
			glog.Infoln(message, e)
		}
	}
}