Recover presence connections after temporary database failures

src/server/presence.ts

@@ -1,5 +1,5 @@
 import type { Server } from 'socket.io';
-import type { GameSessionStore } from './game-session-store.js';
+import { ApiError, type GameSessionStore } from './game-session-store.js';
 import { PRESENCE_AUTH_REFRESH_MS } from '../../constants/presence.js';
 
 // The application is deployed as one process, as is the ranked match service.
@@ -15,7 +15,7 @@ export function registerPresence(io: Server, sessions: GameSessionStore) {
     void sessions.get({ gameSessionId, token }).then(session => {
       socket.data.playerId = session.playerId ?? session.gameSessionId;
       next();
-    }, () => next(new Error('INVALID_SESSION')));
+    }, error => next(new Error(error instanceof ApiError && error.statusCode === 401 ? 'INVALID_SESSION' : 'PRESENCE_UNAVAILABLE')));
   });
   namespace.on('connection', socket => {
     const before = count; publish();
@@ -25,7 +25,10 @@ export function registerPresence(io: Server, sessions: GameSessionStore) {
       if (checking) return;
       checking = true;
       const { gameSessionId, token } = socket.handshake.auth;
-      void sessions.get({ gameSessionId, token }).catch(() => socket.disconnect(true)).finally(() => { checking = false; });
+      void sessions.get({ gameSessionId, token }).catch(error => {
+        if (error instanceof ApiError && error.statusCode === 401) socket.disconnect(true);
+        else socket.conn.close(); // Transport closure permits Socket.IO to reconnect after a transient outage.
+      }).finally(() => { checking = false; });
     }, PRESENCE_AUTH_REFRESH_MS);
     timer.unref();
     socket.on('disconnect', () => { clearInterval(timer); publish(); });