111 lines
3.6 KiB
ReStructuredText
111 lines
3.6 KiB
ReStructuredText
.. _async-injections:
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Asynchronous injections
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=======================
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.. meta::
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:keywords: Python,DI,Dependency injection,IoC,Inversion of Control,Providers,Async,Injections,Asynchronous,Await,
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Asyncio
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:description: Dependency Injector providers support asynchronous injections. This page
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demonstrates how make asynchronous dependency injections in Python.
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Providers support asynchronous injections.
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.. literalinclude:: ../../examples/providers/async.py
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:language: python
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:emphasize-lines: 26-29
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:lines: 3-
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If provider has any awaitable injections it switches into async mode. In async mode provider always returns awaitable.
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This causes a cascade effect:
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.. code-block:: bash
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provider1() <── Async mode enabled <──┐
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│ │
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├──> provider2() │
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│ │
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├──> provider3() <── Async mode enabled <──┤
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│ │ │
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│ └──> provider4() <── Async provider ───────┘
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│
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└──> provider5()
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│
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└──> provider6()
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In async mode provider prepares injections asynchronously.
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If provider has multiple awaitable dependencies, it will run them concurrently. Provider will wait until all
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dependencies are ready and inject them afterwards.
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.. code-block:: bash
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provider1()
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│
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├──> provider2() <── Async mode enabled
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│
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├──> provider3() <── Async mode enabled
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│
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└──> provider4() <── Async mode enabled
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Here is what provider will do for the previous example:
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.. code-block:: python
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injections = await asyncio.gather(
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provider2(),
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provider3(),
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provider4(),
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)
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await provider1(*injections)
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Overriding behaviour
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--------------------
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In async mode provider always returns awaitable. It applies to the overriding too. If provider in async mode is
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overridden by a provider that doesn't return awaitable result, the result will be wrapped into awaitable.
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.. literalinclude:: ../../examples/providers/async_overriding.py
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:language: python
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:emphasize-lines: 19-24
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:lines: 3-
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Async mode mechanics and API
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----------------------------
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By default provider's async mode is undefined.
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When provider async mode is undefined, provider will automatically select the mode during the next call.
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If the result is awaitable, provider will enable async mode, if not - disable it.
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If provider async mode is enabled, provider always returns awaitable. If the result is not awaitable,
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provider wraps it into awaitable explicitly. You can safely ``await`` provider in async mode.
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If provider async mode is disabled, provider behaves the regular way. It doesn't do async injections
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preparation or non-awaitables to awaitables conversion.
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Once provider async mode is enabled or disabled, provider will stay in this state. No automatic switching
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will be done.
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.. image:: images/async_mode.png
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You can also use following methods to change provider's async mode manually:
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- ``Provider.enable_async_mode()``
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- ``Provider.disable_async_mode()``
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- ``Provider.reset_async_mode()``
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To check the state of provider's async mode use:
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- ``Provider.is_async_mode_enabled()``
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- ``Provider.is_async_mode_disabled()``
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- ``Provider.is_async_mode_undefined()``
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See also:
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- Wiring :ref:`async-injections-wiring`
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- Resource provider :ref:`resource-async-initializers`
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- :ref:`fastapi-redis-example`
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.. disqus::
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