57 lines
2.3 KiB
Plaintext
57 lines
2.3 KiB
Plaintext
====================
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Asynchronous support
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====================
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.. versionadded:: 3.0
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Django has developing support for asynchronous ("async") Python, but does not
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yet support asynchronous views or middleware; they will be coming in a future
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release.
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There is limited support for other parts of the async ecosystem; namely, Django
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can natively talk :doc:`ASGI </howto/deployment/asgi/index>`, and some async
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safety support.
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.. _async-safety:
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Async-safety
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------------
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Certain key parts of Django are not able to operate safely in an asynchronous
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environment, as they have global state that is not coroutine-aware. These parts
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of Django are classified as "async-unsafe", and are protected from execution in
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an asynchronous environment. The ORM is the main example, but there are other
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parts that are also protected in this way.
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If you try to run any of these parts from a thread where there is a *running
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event loop*, you will get a
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:exc:`~django.core.exceptions.SynchronousOnlyOperation` error. Note that you
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don't have to be inside an async function directly to have this error occur. If
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you have called a synchronous function directly from an asynchronous function
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without going through something like ``sync_to_async`` or a threadpool, then it
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can also occur, as your code is still running in an asynchronous context.
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If you encounter this error, you should fix your code to not call the offending
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code from an async context; instead, write your code that talks to async-unsafe
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in its own, synchronous function, and call that using
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``asgiref.sync.async_to_sync``, or any other preferred way of running
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synchronous code in its own thread.
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If you are *absolutely* in dire need to run this code from an asynchronous
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context - for example, it is being forced on you by an external environment,
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and you are sure there is no chance of it being run concurrently (e.g. you are
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in a Jupyter_ notebook), then you can disable the warning with the
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``DJANGO_ALLOW_ASYNC_UNSAFE`` environment variable.
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.. warning::
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If you enable this option and there is concurrent access to the
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async-unsafe parts of Django, you may suffer data loss or corruption. Be
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very careful and do not use this in production environments.
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If you need to do this from within Python, do that with ``os.environ``::
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os.environ["DJANGO_ALLOW_ASYNC_UNSAFE"] = "true"
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.. _Jupyter: https://jupyter.org/
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