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https://github.com/vale981/ray
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96 lines
3.2 KiB
ReStructuredText
96 lines
3.2 KiB
ReStructuredText
Virtual Actors
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==============
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Introduction
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------------
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Workflows also provides a *virtual actors* abstraction, which can be thought of as syntactic sugar on top of a dynamic workflow. Virtual actors are like Ray actors, but backed by durable storage instead of a running process. You can also launch sub-workflows from the methods of each virtual actor (e.g., train models in parallel). Here is a basic example:
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.. code-block:: python
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from ray import workflow
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import ray
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@workflow.virtual_actor
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class Counter:
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def __init__(self, init_val):
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self._val = init_val
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def incr(self, val=1):
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self._val += val
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print(self._val)
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@workflow.virtual_actor.readonly
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def value(self):
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return self._val
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workflow.init()
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# Initialize a Counter actor with id="my_counter".
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counter = Counter.get_or_create("my_counter", 0)
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# Similar to workflow steps, actor methods support:
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# - `run()`, which will return the value
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# - `run_async()`, which will return a ObjectRef
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counter.incr.run(10)
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assert counter.value.run() == 10
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# Non-blocking execution.
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counter.incr.run_async(10)
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counter.incr.run(10)
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assert 30 == ray.get(counter.value.run_async())
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In the code above, we define a ``Counter`` virtual actor. When the ``Counter`` is created, its class definition and initial state is logged into storage as a dynamic workflow with ``workflow_id="my_counter"``. When actor methods are called, new steps are dynamically appended to the workflow and executed, returning the new actor state and result.
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``__dict__`` in virtual actors must be able to json serializable, otherwise ``__getstate__`` and ``__setstate__`` must be defined, which will be called on each step to restore and save the actor.
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We can retrieve the actor via its ``workflow_id`` in another process, to get the value:
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.. code-block:: python
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counter = workflow.get_actor(workflow_id="counter")
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assert 30 == counter.value.run()
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Readonly methods are not only lower overhead since they skip action logging, but can be executed concurrently with respect to mutating methods on the actor.
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Launching sub-workflows from actor methods
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------------------------------------------
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In side virtual actor method, a workflow can be launched. Besides this, a workflow can also be passed to actor method:
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.. code-block:: python
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@workflow.step
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def double(s):
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return 2 * s
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@workflow.virtual_actor
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class Actor:
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def __init__(self):
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self.val = 1
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def double(self, update):
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step = double.step(self.val)
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if not update:
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# inside the method, a workflow can be launched
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return step
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else:
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# workflow can also be passed to anthoer method
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return self.update.step(step)
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def update(self, v):
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self.val = v
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return self.val
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handler = Actor.get_or_create("actor")
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assert handler.double.run(False) == 2
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assert handler.double.run(False) == 2
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assert handler.double.run(True) == 2
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assert handler.double.run(True) == 4
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Receiving external events
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-------------------------
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**Note: This feature is not yet implemented.**
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