Enforce room ID uniqueness

[jldinh]

Steps to Reproduce (for bugs)

1. Setup a colyseus cluster with 2 servers and a colyseus proxy (Redis presence and Mongo driver)
2. Create a room with a filter, inspired by step 1 of https://docs.colyseus.io/colyseus/how-to/password-protect-room/

gameServer
  .define("battle", BattleRoom)
  .filterBy(['password'])

3. In the onCreate of BattleRoom, assign a custom roomId

async onCreate(options: any) {
  this.roomId = options.password;
}

4. Use joinOrCreate simultaneously from many clients, with the same password
5. Multiple rooms with the same ID get created, which is at least a problem for the client method joinBy. It seems clients still get split into multiple rooms even if I sort the rooms by ascending creation date.

Context

I was trying to create rooms with a fixed ID matching an ID provided by another service, but this seems to break joinOrCreate.
This seems to be due to a race condition in the finding of a suitable room, which checks there is no room available, then creates one. If two requests are processed simultaneously, two rooms will be created.
I tried making the roomId index in MongoDB unique, but as the colyseus server did not handle the database errors appropriately, I did not investigate this further.
It seems to me we either need:

• to query the DB again for the best available room after creating one
• to make roomIds unique in the DB, and re-query the DB if room creation fails

Your Environment

• Colyseus Version: 0.14.20
• Node.js Version: 14.17.4
• Operating System and version: Ubuntu 20.04

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 7 days.

[jldinh]

bump

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 7 days.

[github-actions]

This issue was closed because it has been stalled for 7 days with no activity.

[karneaud]

bump

[endel]

Hi @karneaud @jldinh, sorry this was closed automatically. I'm assigning a milestone so it won't auto-close again.

Does this happen when roomId is a number, or it doesn't matter if it's a number and/or string?

[karneaud]

@endel never tried it with a number but did not work as a string. But I solved my issue by defining/ using another custom property and it seems to work

[jldinh]

@endel I also only tried with strings.

[oyed]

I'm doing this via a Redis lock personally, enforcing the acquisition of a lock in onCreate and removing it for onDispose, for example:

async onCreate(options) {
  const myCustomId = options.my_custom_id?.toString();

  if (!myCustomId) {
    throw new Error('No ID provided');
  }

  const obtainedLock = await this.presence.pub.set(`room-${myCustomId}`, 1, 'NX');

  if (obtainedLock !== 'OK') {
    throw new Error('Room already exists');
  }

  this.roomId = myCustomId;

  ...
}

async onDispose() {
  await this.presence.pub.del(`room-${this.roomId}`);
}