Dev Mode

How it works?

The devMode option has been introduced to speed up local development when you're updating your server code.

Whenever you update your server code, before the server restarts, all active rooms are cached locally, including their state and sessionId's of previously connected clients (seat reservations). After the restart, all rooms are recreated and the cached state is restored.

The clients are going to try to reconnect as soon as the server goes down, and keep trying a few times until they are successful, or the attempt limit is reached.

(The client-side code is not reloaded, only the connection is re-established)

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Enabling devMode

The devMode is disabled by default and it can be enabled via Server option:

Self-hosted

import { Server } from "colyseus";

const gameServer = new Server({
  // ...
  devMode: true
});

arena.config.ts

import Arena from "@colyseus/arena";

export default Arena({
    // ...
    options: {
        devMode: true
    },
    // ...
});

Attention on the client-side

Upon re-establishing a connection on devMode, the onAdd schema callback will be triggered again on the client-side. Be prepared to possibly ignore it during development.

Do not use devMode in production!

This feature is very costly and is not optimized for a large amount of rooms. Use it for local development only. (Arena hosting does not support this feature)

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Restoring data outside the room's state

• By default, only the state of the room is cached and restored when the server restarts.
• You can restore data outside the room's state by implementing the onCacheRoom() and onRestoreRoom() methods.
• Only JSON-serializable data is allowed.

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onCacheRoom

The onCacheRoom will be executed before the room is cached and disposed.

export class MyRoom extends Room<MyRoomState> {
  // ...

  onCacheRoom() {
    return { foo: "bar" };
  }
}

---

onRestoreRoom

The onRestoreRoom will be executed after the room has been restored and the restored state is available.

The argument provided for the onRestoreRoom is the data previously returned by the onCacheRoom method.

No clients are connected yet at this point.

export class MyRoom extends Room<MyRoomState> {
  // ...

  onRestoreRoom(cachedData: any): void {
    console.log("restoring room", cachedData);

    this.state.players.forEach(player => {
      player.method(cachedData["foo"]);
    });
  }
}