feat(server): gracefully close websocket connections on server shutdo…

…wn (#143)

* feat(server): gracefully close websocket connections on server shutdown

* websocket connections are automatically closed upon server closure

* pr comments

packages/server/src/launcher.ts

@@ -83,8 +83,17 @@ export class Launcher {
     if (!this.shuttingDown) {
       this.shuttingDown = true
 
+      if (!yn(process.env.SPINNED)) {
+        this.logger.info('Server gracefully closing down...')
+      }
+
+      await this.api.sockets.destroy()
       await this.httpTerminator?.terminate()
       await this.app.destroy()
+
+      if (!yn(process.env.SPINNED)) {
+        this.logger.info('Server shutdown complete')
+      }
     }
     process.exit(code)
   }

packages/server/src/socket/manager.ts

@@ -7,17 +7,38 @@ import { SocketService } from './service'
 
 export class SocketManager {
   private logger = new Logger('Socket')
+  private ws: Socket.Server | undefined
   private handlers: { [type: string]: SocketHandler } = {}
 
   constructor(private sockets: SocketService) {}
 
   async setup(server: Server) {
     if (yn(process.env.ENABLE_EXPERIMENTAL_SOCKETS)) {
-      const ws = new Socket.Server(server, { cors: { origin: '*' } })
-      ws.on('connection', this.handleSocketConnection.bind(this))
+      this.ws = new Socket.Server(server, { cors: { origin: '*' } })
+      this.ws.on('connection', this.handleSocketConnection.bind(this))
     }
   }
 
+  async destroy() {
+    if (!this.ws) {
+      return
+    }
+
+    await new Promise((resolve, reject) => {
+      // This is kind of hack to make sure that socket.io does not
+      // try to close the HTTP server before http-terminator
+      this.ws!['httpServer'] = undefined
+
+      this.ws!.close((err) => {
+        if (err) {
+          this.logger.error(err, 'An error occurred when closing the websocket server.')
+        }
+
+        resolve(undefined)
+      })
+    })
+  }
+
   public handle(type: string, callback: SocketHandler) {
     this.handlers[type] = callback
   }