Can I force task/actor to run on specific Node? using Ray

Question

I know that a group of tasks in ray will connect with the same actor/s and this will cause a lot of IO between the actor/s and the tasks.
I want to know if is there a way to force the actor/s and the tasks to run on the same Node, to optimize the IO connection.

Answer 1

For Ray 1.13, you can use ray.util.scheduling_strategies.NodeAffinitySchedulingStrategy(node_id, soft: bool),

Here is a simple example:

@ray.remote
class Actor:
    pass

# "DEFAULT" scheduling strategy is used (packed onto nodes until reaching a threshold and then spread).
a1 = Actor.remote()

# Zero-CPU (and no other resources) actors are randomly assigned to nodes.
a2 = Actor.options(num_cpus=0).remote()

# Only run the actor on the local node.
a3 = Actor.options(
    scheduling_strategy=NodeAffinitySchedulingStrategy(
        node_id = ray.get_runtime_context().node_id,
        soft = False,
    )
).remote()