Why did my server can't handle 150 participants?

Description

Today, I had a session for my client, where I combined a live stream video with a rocket chat channel. That was realized with a simple html page with Iframes. Beginning with showing an Iframe full screen, the user had to login to remove the fullscreen chat and switch to the live stream (via youtube non listed) and a minified Iframe of the channel,
I had around 150 participants (they registered the days before) and after quite a short time, the chat became unresponsive. I monitored the setup with netdata and there was nothing obvious visible, the system / network / disk load was quite low.

So now my question, how can I debug this issue a few hours after the happening and how to avoid it next time?

Server Setup Information

  • Version of Rocket.Chat Server: 3.3.0
  • Operating System: Debian Buster
  • Deployment Method: git
  • Number of Running Instances: 1
  • DB Replicaset Oplog: default
  • NodeJS Version: 12.14.0 - x64
  • MongoDB Version: 4.2.7 (wiredtiger)
  • Proxy: apache 2.4
  • Firewalls involved: —

Kind regards
Dorian

I tried a few scenarios with a lot of self reloading browser tabs to reconstruct the issue where participants only see a loading screen and it got better, after I started a few instances of RocketChat on the samse server. But from time to time the ever loading screen still happens and I really would like to know how to debug it.

Is there a kind of timeout for the client?

Kind regards
Dorian