wehub-resource-sync
33 lines
1.5 KiB
ReStructuredText
33 lines
1.5 KiB
ReStructuredText
.. _ray-get-too-many-objects:
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Anti-pattern: Fetching too many objects at once with ray.get causes failure
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===========================================================================
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**TLDR:** Avoid calling :func:`ray.get() <ray.get>` on too many objects since this will lead to heap out-of-memory or object store out-of-space. Instead fetch and process one batch at a time.
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If you have a large number of tasks that you want to run in parallel, trying to do ``ray.get()`` on all of them at once could lead to failure with heap out-of-memory or object store out-of-space since Ray needs to fetch all the objects to the caller at the same time.
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Instead you should get and process the results one batch at a time. Once a batch is processed, Ray will evict objects in that batch to make space for future batches.
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.. figure:: ../images/ray-get-too-many-objects.svg
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Fetching too many objects at once with ``ray.get()``
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Code example
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------------
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**Anti-pattern:**
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.. literalinclude:: ../doc_code/anti_pattern_ray_get_too_many_objects.py
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:language: python
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:start-after: __anti_pattern_start__
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:end-before: __anti_pattern_end__
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**Better approach:**
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.. literalinclude:: ../doc_code/anti_pattern_ray_get_too_many_objects.py
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:language: python
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:start-after: __better_approach_start__
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:end-before: __better_approach_end__
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Here besides getting one batch at a time to avoid failure, we are also using ``ray.wait()`` to process results in the finish order instead of the submission order to reduce the runtime. See :doc:`ray-get-submission-order` for more details.
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