No state machine in elsa-workflows?

Question

love the elsa-workflows project as I was heavily using WWF in the past. However many of my workflows where state machines. I can't see any in elsa, any plans to support this ?

Answer 1

Elsa 2 does not support the state machine model (only the flowchart model), but I am planning on revising the engine for Elsa 3 which would allow any type of model, including state machine and simple sequential flows like we have in Windows WF.

UPDATE

After I answered with the above I started to think ahead of the state machine architecture for V3, during which I realized we can implement the state machine model already today with V2.

All it would take is a simple new activity called e.g. "State" that has an infinite number of outcomes. This State activity would simply set a workflow variable called e.g. "StateMachineState" or "CurrentState". Each outbound connection would be connected to any trigger responsible for transitioning into the next state. This could be a message from a service bus, a timer, an HTTP request, or anything else that's available with Elsa.

The only real change that would need to be added to make the user experience smooth is the ability to keep adding connections without having to specify them manually from the activity editor. With the current design, we could probably just automatically add an extra outcome to the activity. So initially there would just be e.g. "Transition 1". When that one becomes connected, a "Transition 2" would appear.

Anyway, I am revising my answer to: it's not here yet, but:

1. You can implement it yourself today, and
2. I will add an initial version of the State machine model to either Elsa 2.1 or 2.2, depending on any hidden gotchas I might have failed to see.

UPDATE 2

I just pushed a change that includes a State activity.

With this, you can now easily implement a state machine by adding State activities to your workflow. Here's an example of a traffic light state machine:

This workflow kick starts automatically after 5 seconds, after which it will transition into the "Green" state. Then it stays there for 10 seconds before transitioning into the "Yellow" state. After 5 seconds, it then transitions into the "Red" state, and finally transitions back to the "Green" state after 5 seconds. Then it repeats.

To use the State activity, you specify things:

1. State name.
2. Allowed transitions (the traffic light example includes only one transition per state, but you can specify more than just one).