also, worker.yaml.j2:
- hone worker_name
- remove worker_pid_file entry (would only be used if worker_daemonize
set to true; also, synapse only knows about the container namespace
and thus can not provide the required host-view PID)
- cherry-pick "Ensure worker config exists in systemd service (#7528)"
from synapse d74cdc1a42e8b487d74c214b1d0ca575429d546a:
"check that the worker config file exists instead of silently failing."