Each of those processes is a separate vm, but running on the same host. See: Preview: multi process apps (get your workers here!) - #40 by kurt
Are they “machines”?
VMs.
Do they all share resources that are applied to the main application?
(unless I am mistaken) Each process is entitled to its own cpu/ram alloc.
I’m having a hard time understanding where the resources are generated/created when using multiple processes.
With flyctl --group directive you can target commands at a specific process within a multi-process Fly app. Ex: fly scale vm shared-cpu-2x --group workerhigh -a appname.
You could also scale them out independently: fly scale count workerhigh=8 worker=4 web=2 -a appname.
We used to use multi-process (way back when), but don’t anymore. Unsure what’s the latest on it, tbh.
Btw, an alternative is to run multiple processes in the same VM with a process supervisor to govern 'em all. Ref: Running Multiple Processes Inside A Fly.io App · Fly Docs
Similar: What is the purpose of the "processes" section in [[services]]? - #2 by ignoramous