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* Update main example * Updating wiring module * Update wiring test case name * Implement string imports for wiring * Update example * Refactor implementation * Update front example * Fix a typo in README * Update wiring docs * Update single container example * Update multiple containers example * Update quotes in multiple containers example * Update quotes in single container example * Update decoupled-packages example * Update single and multiple containers example * Update quotes * Update fastapi+redis example * Update resource docs * Update quotes in CLI tutorial * Update CLI application (movie lister) tutorial * Update monitoring daemon example * Update python version in asyncio daemon example * Update asyncio daemon tutorial * Update quotes in wiring docs * Update wiring docs
363 lines
9.0 KiB
ReStructuredText
363 lines
9.0 KiB
ReStructuredText
.. _resource-provider:
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Resource provider
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=================
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.. meta::
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:keywords: Python,DI,Dependency injection,IoC,Inversion of Control,Resource,Injection,
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Logging,Event Loop,Thread Pool
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:description: Resource provider provides a component with initialization and shutdown. It works
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well for configuring logging, event loop, thread or process pool, etc.
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This page demonstrates how to use resource provider.
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.. currentmodule:: dependency_injector.providers
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:py:class:`Resource` provider provides a component with initialization and shutdown.
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.. literalinclude:: ../../examples/providers/resource.py
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:language: python
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:lines: 3-
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Resource providers help to initialize and configure logging, event loop, thread or process pool, etc.
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Resource provider is similar to ``Singleton``. Resource initialization happens only once.
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You can make injections and use provided instance the same way like you do with any other provider.
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.. code-block:: python
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:emphasize-lines: 12
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class Container(containers.DeclarativeContainer):
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config = providers.Configuration()
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thread_pool = providers.Resource(
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init_thread_pool,
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max_workers=config.max_workers,
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)
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dispatcher = providers.Factory(
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TaskDispatcher,
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executor=thread_pool,
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)
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Container has an interface to initialize and shutdown all resources at once:
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.. code-block:: python
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container = Container()
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container.init_resources()
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container.shutdown_resources()
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You can also initialize and shutdown resources one-by-one using ``init()`` and
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``shutdown()`` methods of the provider:
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.. code-block:: python
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container = Container()
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container.thread_pool.init()
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container.thread_pool.shutdown()
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When you call ``.shutdown()`` method on a resource provider, it will remove the reference to the initialized resource,
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if any, and switch to uninitialized state. Some of resource initializer types support specifying custom
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resource shutdown.
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Resource provider supports 3 types of initializers:
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- Function
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- Generator
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- Subclass of ``resources.Resource``
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Function initializer
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--------------------
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Function is the most common way to specify resource initialization:
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.. code-block:: python
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def init_resource(argument1=..., argument2=...):
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return SomeResource()
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class Container(containers.DeclarativeContainer):
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resource = providers.Resource(
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init_resource,
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argument1=...,
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argument2=...,
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)
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Function initializer may not return a value. This often happens when
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you configure global resource:
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.. code-block:: python
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import logging.config
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class Container(containers.DeclarativeContainer):
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configure_logging = providers.Resource(
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logging.config.fileConfig,
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fname="logging.ini",
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)
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Function initializer does not provide a way to specify custom resource shutdown.
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Generator initializer
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---------------------
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Resource provider can use 2-step generators:
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- First step of generator is an initialization phase
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- The second is step is a shutdown phase
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.. code-block:: python
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def init_resource(argument1=..., argument2=...):
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resource = SomeResource() # initialization
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yield resource
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# shutdown
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...
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class Container(containers.DeclarativeContainer):
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resource = providers.Resource(
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init_resource,
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argument1=...,
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argument2=...,
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)
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Generator initialization phase ends on the first ``yield`` statement. You can return a
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resource object using ``yield resource`` like in the example above. Returning of the
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object is not mandatory. You can leave ``yield`` statement empty:
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.. code-block:: python
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def init_resource(argument1=..., argument2=...):
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# initialization
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...
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yield
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# shutdown
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...
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class Container(containers.DeclarativeContainer):
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resource = providers.Resource(
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init_resource,
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argument1=...,
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argument2=...,
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)
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Subclass initializer
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--------------------
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You can create resource initializer by implementing a subclass of the ``resources.Resource``:
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.. code-block:: python
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from dependency_injector import resources
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class MyResource(resources.Resource):
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def init(self, argument1=..., argument2=...) -> SomeResource:
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return SomeResource()
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def shutdown(self, resource: SomeResource) -> None:
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# shutdown
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...
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class Container(containers.DeclarativeContainer):
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resource = providers.Resource(
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MyResource,
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argument1=...,
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argument2=...,
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)
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Subclass must implement two methods: ``init()`` and ``shutdown()``.
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Method ``init()`` receives arguments specified in resource provider.
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It performs initialization and returns resource object. Returning of the object
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is not mandatory.
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Method ``shutdown()`` receives resource object returned from ``init()``. If ``init()``
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didn't return an object ``shutdown()`` method will be called anyway with ``None`` as a
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first argument.
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.. code-block:: python
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from dependency_injector import resources
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class MyResource(resources.Resource):
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def init(self, argument1=..., argument2=...) -> None:
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# initialization
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...
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def shutdown(self, _: None) -> None:
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# shutdown
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...
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.. _resource-provider-wiring-closing:
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Resources, wiring, and per-function execution scope
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---------------------------------------------------
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You can compound ``Resource`` provider with :ref:`wiring` to implement per-function
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execution scope. For doing this you need to use additional ``Closing`` marker from
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``wiring`` module.
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.. literalinclude:: ../../examples/wiring/flask_resource_closing.py
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:language: python
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:lines: 3-
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:emphasize-lines: 22
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Framework initializes and injects the resource into the function. With the ``Closing`` marker
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framework calls resource ``shutdown()`` method when function execution is over.
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The example above produces next output:
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.. code-block:: bash
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Init service
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Shutdown service
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127.0.0.1 - - [29/Oct/2020 22:39:40] "GET / HTTP/1.1" 200 -
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Init service
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Shutdown service
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127.0.0.1 - - [29/Oct/2020 22:39:41] "GET / HTTP/1.1" 200 -
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Init service
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Shutdown service
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127.0.0.1 - - [29/Oct/2020 22:39:41] "GET / HTTP/1.1" 200 -
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.. _resource-async-initializers:
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Asynchronous initializers
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-------------------------
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When you write an asynchronous application, you might need to initialize resources asynchronously. Resource
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provider supports asynchronous initialization and shutdown.
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Asynchronous function initializer:
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.. code-block:: python
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async def init_async_resource(argument1=..., argument2=...):
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return await connect()
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class Container(containers.DeclarativeContainer):
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resource = providers.Resource(
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init_resource,
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argument1=...,
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argument2=...,
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)
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Asynchronous generator initializer:
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.. code-block:: python
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async def init_async_resource(argument1=..., argument2=...):
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connection = await connect()
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yield connection
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await connection.close()
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class Container(containers.DeclarativeContainer):
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resource = providers.Resource(
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init_async_resource,
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argument1=...,
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argument2=...,
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)
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Asynchronous subclass initializer:
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.. code-block:: python
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from dependency_injector import resources
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class AsyncConnection(resources.AsyncResource):
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async def init(self, argument1=..., argument2=...):
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yield await connect()
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async def shutdown(self, connection):
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await connection.close()
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class Container(containers.DeclarativeContainer):
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resource = providers.Resource(
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AsyncConnection,
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argument1=...,
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argument2=...,
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)
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When you use resource provider with asynchronous initializer you need to call its ``__call__()``,
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``init()``, and ``shutdown()`` methods asynchronously:
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.. code-block:: python
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import asyncio
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class Container(containers.DeclarativeContainer):
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connection = providers.Resource(init_async_connection)
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async def main():
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container = Container()
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connection = await container.connection()
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connection = await container.connection.init()
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connection = await container.connection.shutdown()
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if __name__ == "__main__":
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asyncio.run(main())
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Container ``init_resources()`` and ``shutdown_resources()`` methods should be used asynchronously if there is
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at least one asynchronous resource provider:
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.. code-block:: python
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import asyncio
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class Container(containers.DeclarativeContainer):
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connection1 = providers.Resource(init_async_connection)
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connection2 = providers.Resource(init_sync_connection)
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async def main():
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container = Container()
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await container.init_resources()
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await container.shutdown_resources()
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if __name__ == "__main__":
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asyncio.run(main())
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See also:
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- Provider :ref:`async-injections`
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- Wiring :ref:`async-injections-wiring`
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- :ref:`fastapi-redis-example`
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.. disqus::
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