Minetrack/assets/js/socket.js

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JavaScript
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export class SocketManager {
constructor (app) {
this._app = app
this._hasRequestedHistoryGraph = false
this._reconnectDelayBase = 0
}
reset () {
this._hasRequestedHistoryGraph = false
}
createWebSocket () {
let webSocketProtocol = 'ws:'
if (location.protocol === 'https:') {
webSocketProtocol = 'wss:'
}
this._webSocket = new WebSocket(`${webSocketProtocol}//${location.host}`)
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// The backend will automatically push data once connected
this._webSocket.onopen = () => {
this._app.caption.set('Loading...')
// Reset reconnection scheduling since the WebSocket has been established
this._reconnectDelayBase = 0
}
this._webSocket.onclose = (event) => {
this._app.handleDisconnect()
// Modify page state to display loading overlay
// Code 1006 denotes "Abnormal closure", most likely from the server or client losing connection
// See https://developer.mozilla.org/en-US/docs/Web/API/CloseEvent
// Treat other codes as active errors (besides connectivity errors) when displaying the message
if (event.code === 1006) {
this._app.caption.set('Lost connection!')
} else {
this._app.caption.set('Disconnected due to error.')
}
// Schedule socket reconnection attempt
this.scheduleReconnect()
}
this._webSocket.onmessage = (message) => {
const payload = JSON.parse(message.data)
switch (payload.message) {
case 'init':
this._app.setPublicConfig(payload.config)
// Display the main page component
// Called here instead of syncComplete so the DOM can be drawn prior to the graphs being drawn
this._app.setPageReady(true)
// Allow the graphDisplayManager to control whether or not the historical graph is loaded
// Defer to isGraphVisible from the publicConfig to understand if the frontend will ever receive a graph payload
if (this._app.publicConfig.isGraphVisible) {
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this.sendHistoryGraphRequest()
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}
payload.servers.forEach((serverPayload, serverId) => {
this._app.addServer(serverId, serverPayload, payload.timestampPoints)
})
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// Init payload contains all data needed to render the page
// Alert the app it is ready
this._app.handleSyncComplete()
break
case 'updateServers': {
for (let serverId = 0; serverId < payload.updates.length; serverId++) {
// The backend may send "update" events prior to receiving all "add" events
// A server has only been added once it's ServerRegistration is defined
// Checking undefined protects from this race condition
const serverRegistration = this._app.serverRegistry.getServerRegistration(serverId)
const serverUpdate = payload.updates[serverId]
if (serverRegistration) {
serverRegistration.handlePing(serverUpdate, payload.timestamp)
serverRegistration.updateServerStatus(serverUpdate, this._app.publicConfig.minecraftVersions)
}
}
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// Bulk add playerCounts into graph during #updateHistoryGraph
if (payload.updateHistoryGraph) {
this._app.graphDisplayManager.addGraphPoint(payload.timestamp, Object.values(payload.updates).map(update => update.playerCount))
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// Run redraw tasks after handling bulk updates
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this._app.graphDisplayManager.redraw()
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}
this._app.percentageBar.redraw()
this._app.updateGlobalStats()
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break
}
case 'historyGraph': {
this._app.graphDisplayManager.buildPlotInstance(payload.timestamps, payload.graphData)
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// Build checkbox elements for graph controls
let lastRowCounter = 0
let controlsHTML = ''
this._app.serverRegistry.getServerRegistrations()
.map(serverRegistration => serverRegistration.data.name)
.sort()
.forEach(serverName => {
const serverRegistration = this._app.serverRegistry.getServerRegistration(serverName)
controlsHTML += `<td><label>
<input type="checkbox" class="graph-control" minetrack-server-id="${serverRegistration.serverId}" ${serverRegistration.isVisible ? 'checked' : ''}>
${serverName}
</label></td>`
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// Occasionally break table rows using a magic number
if (++lastRowCounter % 6 === 0) {
controlsHTML += '</tr><tr>'
}
})
// Apply generated HTML and show controls
document.getElementById('big-graph-checkboxes').innerHTML = `<table><tr>${controlsHTML}</tr></table>`
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document.getElementById('big-graph-controls').style.display = 'block'
// Bind click event for updating graph data
this._app.graphDisplayManager.initEventListeners()
break
}
}
}
}
scheduleReconnect () {
// Release any active WebSocket references
this._webSocket = undefined
this._reconnectDelayBase++
// Exponential backoff for reconnection attempts
// Clamp ceiling value to 30 seconds
this._reconnectDelaySeconds = Math.min((this._reconnectDelayBase * this._reconnectDelayBase), 30)
const reconnectInterval = setInterval(() => {
this._reconnectDelaySeconds--
if (this._reconnectDelaySeconds === 0) {
// Explicitly clear interval, this avoids race conditions
// #clearInterval first to avoid potential errors causing pre-mature returns
clearInterval(reconnectInterval)
// Update displayed text
this._app.caption.set('Reconnecting...')
// Attempt reconnection
// Only attempt when reconnectDelaySeconds === 0 and not <= 0, otherwise multiple attempts may be started
this.createWebSocket()
} else if (this._reconnectDelaySeconds > 0) {
// Update displayed text
this._app.caption.set(`Reconnecting in ${this._reconnectDelaySeconds}s...`)
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}
}, 1000)
}
sendHistoryGraphRequest () {
if (!this._hasRequestedHistoryGraph) {
this._hasRequestedHistoryGraph = true
// Send request as a plain text string to avoid the server needing to parse JSON
// This is mostly to simplify the backend server's need for error handling
this._webSocket.send('requestHistoryGraph')
}
}
}