wehub-resource-sync
34 lines
1.7 KiB
ReStructuredText
34 lines
1.7 KiB
ReStructuredText
Pattern: Using asyncio to run actor methods concurrently
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========================================================
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By default, a Ray :ref:`actor <ray-remote-classes>` runs in a single thread and
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actor method calls are executed sequentially. This means that a long running method call blocks all the following ones.
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In this pattern, we use ``await`` to yield control from the long running method call so other method calls can run concurrently.
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Normally the control is yielded when the method is doing IO operations but you can also use ``await asyncio.sleep(0)`` to yield control explicitly.
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.. note::
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You can also use :ref:`threaded actors <threaded-actors>` to achieve concurrency.
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Example use case
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----------------
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You have an actor with a long polling method that continuously fetches tasks from the remote store and executes them.
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You also want to query the number of tasks executed while the long polling method is running.
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With the default actor, the code will look like this:
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.. literalinclude:: ../doc_code/pattern_async_actor.py
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:language: python
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:start-after: __sync_actor_start__
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:end-before: __sync_actor_end__
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This is problematic because ``TaskExecutor.run`` method runs forever and never yields control to run other methods.
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We can solve this problem by using :ref:`async actors <async-actors>` and use ``await`` to yield control:
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.. literalinclude:: ../doc_code/pattern_async_actor.py
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:language: python
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:start-after: __async_actor_start__
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:end-before: __async_actor_end__
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Here, instead of using the blocking :func:`ray.get() <ray.get>` to get the value of an ObjectRef, we use ``await`` so it can yield control while we are waiting for the object to be fetched.
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