I have been looking for a way to change the number of WORKER_PROCESSES of the forum plugin, but the change is not reflected.
I did was edit the Dockerfile located at .local/share/tutor/env/plugins/forum/build/forum, adding the ENV WORKER_PROCESSES "10" and rebuild the image with the command tutor images build forum, restart the container but I still see the same 4 processes.
Not the best solution but this is what worked for me.
As I see that the image does not generate the file with the environment variables to start the forums and be able to change the number of workers, what I did was the following:
Edit the Dockerfile from the forums add the line RUN sed -i 's/4)/6)/g' ./config/unicorn_tcp.rb under RUN bundle install --deployment
Replace the 6 with the number of workers we need
Then we remake the image with the command tutor images build forum and restart the forums tutor local restart forum