Minetrack/lib/servers.js

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const crypto = require('crypto')
const dns = require('dns')
const { GRAPH_UPDATE_TIME_GAP, TimeTracker } = require('./time')
const Server = require('./server')
const { getPlayerCountOrNull } = require('./util')
const config = require('../config')
const minecraftVersions = require('../minecraft_versions')
class ServerRegistration {
serverId
lastFavicon
versions = []
recordData
graphData = []
constructor (app, serverId, data) {
this._app = app
this.serverId = serverId
this.data = data
this._pingHistory = []
}
handlePing (timestamp, resp, err, version, updateHistoryGraph) {
// Use null to represent a failed ping
const unsafePlayerCount = getPlayerCountOrNull(resp)
// Store into in-memory ping data
TimeTracker.pushAndShift(this._pingHistory, unsafePlayerCount, TimeTracker.getMaxServerGraphDataLength())
// Only notify the frontend to append to the historical graph
// if both the graphing behavior is enabled and the backend agrees
// that the ping is eligible for addition
if (updateHistoryGraph) {
TimeTracker.pushAndShift(this.graphData, unsafePlayerCount, TimeTracker.getMaxGraphDataLength())
}
// Delegate out update payload generation
return this.getUpdate(timestamp, resp, err, version)
}
getUpdate (timestamp, resp, err, version) {
const update = {}
if (resp) {
if (resp.version && this.updateProtocolVersionCompat(resp.version, version.protocolId, version.protocolIndex)) {
// Append an updated version listing
update.versions = this.versions
}
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if (config.logToDatabase && (!this.recordData || resp.players.online > this.recordData.playerCount)) {
this.recordData = {
playerCount: resp.players.online,
timestamp: TimeTracker.toSeconds(timestamp)
}
// Append an updated recordData
update.recordData = this.recordData
}
if (this.updateFavicon(resp.favicon)) {
update.favicon = this.getFaviconUrl()
}
// Append a result object
// This filters out unwanted data from resp
update.playerCount = resp.players.online
if (config.logToDatabase) {
// Update calculated graph peak regardless if the graph is being updated
// This can cause a (harmless) desync between live and stored data, but it allows it to be more accurate for long surviving processes
if (this.findNewGraphPeak()) {
update.graphPeakData = this.getGraphPeak()
}
}
} else if (err) {
// Append a filtered copy of err
// This ensures any unintended data is not leaked
update.error = this.filterError(err)
}
return update
}
getPingHistory () {
if (this._pingHistory.length > 0) {
const payload = {
versions: this.versions,
recordData: this.recordData,
favicon: this.getFaviconUrl()
}
// Only append graphPeakData if defined
// The value is lazy computed and conditional that config->logToDatabase == true
const graphPeakData = this.getGraphPeak()
if (graphPeakData) {
payload.graphPeakData = graphPeakData
}
// Assume the ping was a success and define result
// pingHistory does not keep error references, so its impossible to detect if this is an error
// It is also pointless to store that data since it will be short lived
payload.playerCount = this._pingHistory[this._pingHistory.length - 1]
// Send a copy of pingHistory
// Include the last value even though it is contained within payload
// The frontend will only push to its graphData from playerCountHistory
payload.playerCountHistory = this._pingHistory
return payload
}
return {
error: {
message: 'Pinging...'
},
recordData: this.recordData,
graphPeakData: this.getGraphPeak(),
favicon: this.data.favicon
}
}
loadGraphPoints (startTime, timestamps, points) {
this.graphData = TimeTracker.everyN(timestamps, startTime, GRAPH_UPDATE_TIME_GAP, (i) => points[i])
}
findNewGraphPeak () {
let index = -1
for (let i = 0; i < this.graphData.length; i++) {
const point = this.graphData[i]
if (index === -1 || point > this.graphData[index]) {
index = i
}
}
if (index >= 0) {
const lastGraphPeakIndex = this._graphPeakIndex
this._graphPeakIndex = index
return index !== lastGraphPeakIndex
} else {
this._graphPeakIndex = undefined
return false
}
}
getGraphPeak () {
if (this._graphPeakIndex === undefined) {
return
}
return {
playerCount: this.graphData[this._graphPeakIndex],
timestamp: this._app.timeTracker.getGraphPointAt(this._graphPeakIndex)
}
}
updateFavicon (favicon) {
// If data.favicon is defined, then a favicon override is present
// Disregard the incoming favicon, regardless if it is different
if (this.data.favicon) {
return false
}
if (favicon && favicon !== this.lastFavicon) {
this.lastFavicon = favicon
// Generate an updated hash
// This is used by #getFaviconUrl
this.faviconHash = crypto.createHash('md5').update(favicon).digest('hex').toString()
return true
}
return false
}
getFaviconUrl () {
if (this.faviconHash) {
return Server.getHashedFaviconUrl(this.faviconHash)
} else if (this.data.favicon) {
return this.data.favicon
}
}
updateProtocolVersionCompat (incomingId, outgoingId, protocolIndex) {
// If the result version matches the attempted version, the version is supported
const isSuccess = incomingId === outgoingId
const indexOf = this.versions.indexOf(protocolIndex)
// Test indexOf to avoid inserting previously recorded protocolIndex values
if (isSuccess && indexOf < 0) {
this.versions.push(protocolIndex)
// Sort versions in ascending order
// This matches protocol ids to Minecraft versions release order
this.versions.sort((a, b) => a - b)
return true
} else if (!isSuccess && indexOf >= 0) {
this.versions.splice(indexOf, 1)
return true
}
return false
}
getNextProtocolVersion () {
// Minecraft Bedrock Edition does not have protocol versions
if (this.data.type === 'PE') {
return {
protocolId: 0,
protocolIndex: 0
}
}
const protocolVersions = minecraftVersions[this.data.type]
if (typeof this._nextProtocolIndex === 'undefined' || this._nextProtocolIndex + 1 >= protocolVersions.length) {
this._nextProtocolIndex = 0
} else {
this._nextProtocolIndex++
}
return {
protocolId: protocolVersions[this._nextProtocolIndex].protocolId,
protocolIndex: this._nextProtocolIndex
}
}
filterError (err) {
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let message = 'Unknown error'
// Attempt to match to the first possible value
for (const key of ['message', 'description', 'errno']) {
if (err[key]) {
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message = err[key]
break
}
}
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// Trim the message if too long
if (message.length > 28) {
message = message.substring(0, 28) + '...'
}
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return {
message: message
}
}
getPublicData () {
// Return a custom object instead of data directly to avoid data leakage
return {
name: this.data.name,
ip: this.data.ip,
type: this.data.type,
color: this.data.color
}
}
unfurlSrv (callback) {
// Skip unfurling SRV, instantly return pre-configured data
if (config.performance && config.performance.skipUnfurlSrv) {
callback(this.data.ip, this.data.port)
return
}
const timestamp = new Date().getTime()
// If a cached copy exists and is within its TTL, instantly return
if (this._lastUnfurlSrv && timestamp - this._lastUnfurlSrv.timestamp <= config.performance.unfurlSrvCacheTtl) {
callback(this._lastUnfurlSrv.ip, this._lastUnfurlSrv.port)
return
}
// Group callbacks into an array
// Once resolved, fire callbacks sequentially
// This avoids callbacks possibly executing out of order
if (!this._unfurlSrvCallbackQueue) {
this._unfurlSrvCallbackQueue = []
}
this._unfurlSrvCallbackQueue.push(callback)
// Prevent multiple #resolveSrv calls per ServerRegistration
if (!this._isUnfurlingSrv) {
this._isUnfurlingSrv = true
dns.resolveSrv('_minecraft._tcp' + this.data.ip, (_, records) => {
this._lastUnfurlSrv = {
timestamp
}
if (records && records.length > 0) {
this._lastUnfurlSrv.ip = records[0].name
this._lastUnfurlSrv.port = records[0].port
} else {
// Provide fallback to pre-configured data
this._lastUnfurlSrv.ip = this.data.ip
this._lastUnfurlSrv.port = this.data.port
}
// Fire the waiting callbacks in queue
// Release blocking flag to allow new #resolveSrv calls
this._isUnfurlingSrv = false
for (const callback of this._unfurlSrvCallbackQueue) {
callback(this._lastUnfurlSrv.ip, this._lastUnfurlSrv.port)
}
// Reset the callback queue
this._unfurlSrvCallbackQueue = []
})
}
}
}
module.exports = ServerRegistration