ray/doc/source/ray-design-patterns/tree-of-actors.rst

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Pattern: Tree of actors
=======================
Example use case
----------------
You want to train 3 models at the same time, while being able to checkpoint/inspect its state.
In this pattern, a collection of Ray worker actors is managed by a supervisory Ray actor.
.. figure:: tree-of-actors.svg
Tree of actors
A single call to the supervisor actor triggers the dispatch of multiple method calls to child actors. The supervisor can process results or update child actors prior to returning.
Notes
-----
- If the supervisor dies (or the driver), the worker actors are automatically terminated thanks to actor reference counting.
- Actors can be nested to multiple levels to form a tree.
Code example
------------
.. code-block:: python
@ray.remote(num_cpus=1)
class Worker:
def work(self):
return "done"
@ray.remote(num_cpus=1)
class Supervisor:
def __init__(self):
self.workers = [Worker.remote() for _ in range(3)]
def work(self):
return ray.get([w.work.remote() for w in self.workers])
ray.init()
sup = Supervisor.remote()
print(ray.get(sup.work.remote())) # outputs ['done', 'done', 'done']