Send healthcheck to maintain ALB connection

Author: Yong Hoon Shin

src/sidebar/models/Party.ts

@@ -13,6 +13,7 @@ import { User, OwnUser, OtherUser } from "./User";
 import { formatTime } from "@/util/formatTime";
 
 const SEND_TIME_UPDATE_INTERVAL = 500;
+const SEND_HEALTH_CHECK_INTERVAL = 1000 * 60; // 60 seconds
 
 export class Party extends EventEmitter<PartyEvent> {
   wsUrl: string;
@@ -23,6 +24,7 @@ export class Party extends EventEmitter<PartyEvent> {
   ownUser!: OwnUser;
   showToast: boolean;
   periodicUpdateIntervalID: number;
+  serverHealthCheckSendIntervalID: number;
 
   constructor(
     wsUrl: string,
@@ -37,6 +39,7 @@ export class Party extends EventEmitter<PartyEvent> {
     parentCommunicator.setParty(this);
     this.parentCommunicator = parentCommunicator;
     this.periodicUpdateIntervalID = -1;
+    this.serverHealthCheckSendIntervalID = -1;
 
     // cleanup if we lose connection with Websocket server by tab/window/browser closing
     window.addEventListener("beforeunload", event => {
@@ -196,6 +199,7 @@ export class Party extends EventEmitter<PartyEvent> {
     this.socket.onopen = () => {
       this.emit(PartyEvent.CONNECTED);
       this.socket.onmessage = this.handleMessage.bind(this);
+      this.sendHealthCheckToServer();
     };
 
     this.socket.onclose = () => {
@@ -211,6 +215,19 @@ export class Party extends EventEmitter<PartyEvent> {
     };
   }
 
+  sendHealthCheckToServer() {
+    // AWS ALB closes idle connections after 200s (for now)
+    // we send health update every minute
+    this.serverHealthCheckSendIntervalID = window.setInterval(async () => {
+      this.socket.send(
+        JSON.stringify({
+          type: SocketSendMsgType.HEALTH_CHECK,
+          payload: {}
+        })
+      );
+    }, SEND_HEALTH_CHECK_INTERVAL);
+  }
+
   checkIfPeriodicallySendVideoTime() {
     if (this.periodicUpdateIntervalID === -1) {
       // CHECK IF WE NEED TO START SENDING UPDATES

src/sidebar/models/types.ts

@@ -44,7 +44,8 @@ export enum SocketSendMsgType {
   NEW_SIGNAL = "newSignal",
   BROADCAST_MESSAGE = "broadcastMessage",
   SET_USER_MUTE = "setUserMute",
-  SET_ADMIN_CONTROLS = "setAdminControls"
+  SET_ADMIN_CONTROLS = "setAdminControls",
+  HEALTH_CHECK = "healthCheck"
 }
 
 export enum RTCMsgType {