Laravel Reverb not connecting with thousand of users in Docker

We are running Laravel Reverb in the offical docker PHP container

Currently we have a lots of users connecting trough reverb and we notice that people can’t connect to the reverb when we have lots (thousands) of users.

We already checked open file descriptor limit and the limits are set very high on the docker container and on the machine its running on. Also the PHP process has a high limit of open file descriptors.

The only notice we get is that we can increase the FD_SETSIZE (which seems to have a connection to open file descriptors) but we do not find this in the Laravel reverb docs or have a good source how to increase that properly

Before we want to setup the scaling we want to ensure every container can handle as many requests as possible so we are curious if there are some best practices that we can integrate in our deployment?