Communication between state machines

[svinopterix]

Is any way to communicate between state machines? We need to avoid parallel executions of specific state if several state machines run in parallel.

[Fryguy]

I can't recall if parallel state machines share a workspace on the server side or if they are separate workspace instances. Can you try having 2 state machines write something into the root object and see if they appear on the other side?

[svinopterix]

I've made simple state machine with a single state as follows and run two of them using call_instance in simulation. No, they don't see each other.

[Fryguy]

Ok, that's what I was concerned about. I recall work done by @dtrieu80 at Red Hat to create a locking concept. You can see some of that in https://talk.manageiq.org/t/automate-engine-region-level-mutex/1185 and in #6577. We never merged it because of concerns about deadlocks within the automation engine, and eventually it went stale. You might be able to resurrect that idea.

Another alternative could be to use Generic Objects. I could envision a "Mutex" Generic Object Definition and Generic Object, where each of the parallel state machine reference the same one, but only one can hold the lock. While the others do not have the lock they can't proceed and/or go into a retry.

[svinopterix]

Thank you for the idea.