Websocket-server peaks at 100% all the time

Infos:

  • Used Zammad version: 3.6.0-1605614796.0157dc25.buster
  • Used Zammad installation source: Debian package
  • Operating system: Debian 10
  • Browser + version: Various

Expected behavior:

  • Zammad runs smoothly and shows changes within 2-3 seconds. The websocket server should not use much CPU as it just forwards messages (?)

Actual behavior:

  • Zammad runs extremely slow (mean delay around 30 seconds, with peaks over 1 minute). The websocket server runs at 100% CPU for most of the time.

Steps to reproduce the behavior:

  • Standard installation with chat integration enabled
  • The problem starts when the number of supporters goes above around 10-15. In the peak we have 40-50 supporters concurrently online with support coming in just via chat, and then the system is rather unusable.
  • We have web workers set to 8 and schedulers set to 4 on a 16-core machine. The CPU utilization of all these processes is fine.
  • We already tried this without any improvement: https://github.com/zammad/zammad/issues/3076