[workflow] create a virtual actor from a virtual actor

When one virtual actor is created, sometimes the user want to duplicate the virtual actor like fork. One way to do this is to get the content of the virtual actor and create another virtual actor. But there is one limitation for this way since sometimes the user doesn’t have the code.

Another and more efficient way to do this is to copy from storage. Here I propose the following API:

@PublicAPI(stability="beta")
def get_actor(actor_id: str, create_from:Optional[str]=None ) -> "VirtualActor":

workflow.get_actor(actor_id="xxx", from_actor_id="yyy")

so this will create a virtual actor xxx from virtual actor yyy. It xxx has already been created, it’ll just return.

[iycheng]

@iycheng In the following code segment, would the estimator inside new_va be a different object from the estimator inside old_va? Or new_va and old_va might still share the same estimator object?

@ray.workflow.virtual_actor
class MLNode():
    def __init__(self, estimator: BaseEstimator):
        if estimator is not None:
            self.estimator = estimator

    @workflow.virtual_actor.readonly
    def get_model(self):
        return self.estimator

    def __getstate__(self):
        return self.estimator

    def __setstate__(self, estimator):
        self.estimator = estimator

logistic = LogisticRegression(max_iter=10000, tol=0.1)
old_va = MLNode.get_or_create('old_va_name', logistic)
new_va = workflow.get_or_create('new_va_name', 'old_va_name')

They will be different, even in the storage layer.

you should treat them as a different virtual actor.

[lchu-ibm]

@iycheng sure, I can look into the namespace feature.