Server handles messages out-of-order when beforeHandleMessage is used

[raimohanska]

Description

If you use an asynchronous beforeHandleMessage hook, you will very likely have messages handled out-of-order. In here there's no mechanism for guaranteeing processing order.

In many cases this is not an issue, but sometimes it leads to inconsistent transient states when processing Y.js updates out of order. I'm not sure what other effects this may have, as this affects all other incoming WebSocket messages as well.

My suggestion would be to guarantee processing order using a queue mechanism.

Steps to reproduce the bug

Add an asynchronous beforeHandleMessage hook. For worst case, add big random delays in your hook to mess up message processing order totally.

Expected behavior

I would expect messages to be processed FIFO.