zammad/doc/developer_manual/cookbook/how-to-debug-zammad-processes.md

How to Debug Zammad Processes

Sometimes it can be helpful to understand the internal state of threads running in a Zammad process. This can be achieved by sending a SIGWINCH signal to any Zammad service (railsserver, websocket or background worker) process, which will cause the process to print the state of its threads to STDOUT.

• Find out process ID of Zammad webserver

  $ ps
  PID TTY           TIME CMD
  …
  77926 ttys001    0:03.02 puma 6.5.0 (tcp://localhost:3000) [zammad]
  …
  

• Send the SIGWINCH signal to that process or any of its forked workers. This doesn't acutally "kill" the process.

  kill -SIGWINCH 77926
  

• Observe the log output in the process' STDOUT, e.g. via journalctl

  PID: 77926 Thread: TID-jqk AR Pool Reaper
  /path/to/gems/ruby-3.2.4/gems/activerecord-7.2.2.1/lib/active_record/connection_adapters/abstract/connection_pool/reaper.rb:49:in `sleep'
  /path/to/gems/ruby-3.2.4/gems/activerecord-7.2.2.1/lib/active_record/connection_adapters/abstract/connection_pool/reaper.rb:49:in `block in spawn_thread'
  PID: 77926 Thread: TID-jr4 listen-wait_thread
  <internal:thread_sync>:18:in `pop'
  /path/to/rubies/ruby-3.2.4/lib/ruby/3.2.0/forwardable.rb:240:in `pop'
  /path/to/gems/ruby-3.2.4/gems/listen-3.9.0/lib/listen/event/processor.rb:89:in `_wait_until_events'
  /path/to/gems/ruby-3.2.4/gems/listen-3.9.0/lib/listen/event/processor.rb:21:in `block in loop_for'
  …