Django 简介
管网有
为什么应用异步
- 因为Djnago在4.0版本之后是反对异步且在4.1里的ORM甚至不须要应用sync_to_async来装璜，rest框架是不反对的协程，在这种状况下应用rest框架会阻塞协程流程.
- 异步根本是web服务开发的趋势，像web框架有fastapi,sanic这些异步框架，Django作为老牌框架像异步迁徙是必然的。
为什么要复写rest_framework局部函数
- 因为Django是协程，然而rest不是，会导致调用中途梗塞，python的协程代码一旦有同步代码则全程同步（毕竟每段代码不是子线程）
代码
generics.py
import asyncioimport inspectfrom asgiref.sync import sync_to_asyncfrom rest_framework import exceptions, statusfrom rest_framework.generics import GenericAPIView, get_object_or_404from rest_framework.request import Requestfrom rest_framework.views import APIViewfrom tortoise import Modelfrom tortoise.queryset import QuerySetfrom async_drf import mixinsclass AsyncAPIView(APIView): """ 参考: https://github.com/encode/django-rest-framework/issues/7260 Provides async view compatible support for DRF Views and ViewSets. This must be the first inherited class. """ @classmethod def as_view(cls, *args, **initkwargs): """Make Django process the view as an async view.""" view = super().as_view(*args, **initkwargs) async def async_view(*args, **kwargs): # wait for the `dispatch` method return await view(*args, **kwargs) async_view.cls = cls async_view.initkwargs = initkwargs async_view.csrf_exempt = True return async_view async def get_exception_handler_context(self): # 返回异样上下文 return await sync_to_async(super().get_exception_handler_context)() async def get_exception_handler(self): # 不管异样函数是不是协程 return super().get_exception_handler() async def handle_exception(self, exc): """ Handle any exception that occurs, by returning an appropriate response, or re-raising the error. """ if isinstance(exc, (exceptions.NotAuthenticated, exceptions.AuthenticationFailed)): # WWW-Authenticate header for 401 responses, else coerce to 403 auth_header = await sync_to_async(self.get_authenticate_header)(self.request) if auth_header: exc.auth_header = auth_header else: exc.status_code = status.HTTP_403_FORBIDDEN exception_handler = await self.get_exception_handler() context = await self.get_exception_handler_context() # 如果自定义异样函数不是协程 if not asyncio.iscoroutinefunction(exception_handler): response = await sync_to_async(exception_handler)(exc, context) else: response = await exception_handler(exc, context) if response is None: await sync_to_async(self.raise_uncaught_exception)(exc) response.exception = True return response async def initialize_request(self, request, *args, **kwargs): """ Returns the initial request object. """ parser_context = self.get_parser_context(request) return Request( request, parsers=self.get_parsers(), authenticators=self.get_authenticators(), negotiator=self.get_content_negotiator(), parser_context=parser_context, ) async def dispatch(self, request, *args, **kwargs): """Add async support.""" self.args = args self.kwargs = kwargs request = await self.initialize_request(request, *args, **kwargs) self.request = request self.headers = self.default_response_headers try: await sync_to_async(self.initial)(request, *args, **kwargs) if request.method.lower() in self.http_method_names: handler = getattr(self, request.method.lower(), self.http_method_not_allowed) else: handler = self.http_method_not_allowed # accept both async and sync handlers # built-in handlers are sync handlers if not asyncio.iscoroutinefunction(handler): handler = sync_to_async(handler) response = await handler(request, *args, **kwargs) except Exception as exc: response = await self.handle_exception(exc) self.response = self.finalize_response(request, response, *args, **kwargs) return self.responseclass AsyncGenericAPIView(AsyncAPIView, GenericAPIView): async def paginate_queryset(self, queryset): """ Return a single page of results, or `None` if pagination is disabled. """ if self.paginator is None: return None return await self.paginator.paginate_queryset(queryset, self.request, view=self) async def get_queryset(self) -> QuerySet: """ Get the list of items for this view. This must be an iterable, and may be a queryset. Defaults to using `self.queryset`. This method should always be used rather than accessing `self.queryset` directly, as `self.queryset` gets evaluated only once, and those results are cached for all subsequent requests. You may want to override this if you need to provide different querysets depending on the incoming request. (Eg. return a list of items that is specific to the user) """ assert self.queryset is not None, ( "'%s' should either include a `queryset` attribute, " "or override the `get_queryset()` method." % self.__class__.__name__ ) queryset = self.queryset if isinstance(queryset, QuerySet): # Ensure queryset is re-evaluated on each request. queryset = queryset.all() return queryset async def get_object(self) -> Model: """ Returns the object the view is displaying. You may want to override this if you need to provide non-standard queryset lookups. Eg if objects are referenced using multiple keyword arguments in the url conf. """ queryset = await self.filter_queryset(await self.get_queryset()) # Perform the lookup filtering. lookup_url_kwarg = self.lookup_url_kwarg or self.lookup_field assert lookup_url_kwarg in self.kwargs, ( "Expected view %s to be called with a URL keyword argument " 'named "%s". Fix your URL conf, or set the `.lookup_field` ' "attribute on the view correctly." % (self.__class__.__name__, lookup_url_kwarg) ) filter_kwargs = {self.lookup_field: self.kwargs[lookup_url_kwarg]} obj = await sync_to_async(get_object_or_404)(queryset, **filter_kwargs) obj = await obj # May raise a permission denied await sync_to_async(self.check_object_permissions)(self.request, obj) return obj async def get_serializer(self, *args, **kwargs): """ Return the serializer instance that should be used for validating and deserializing input, and for serializing output. """ if inspect.iscoroutinefunction(self.get_serializer_class): serializer_class = await self.get_serializer_class() else: serializer_class = await sync_to_async(self.get_serializer_class)() kwargs.setdefault("context", await sync_to_async(self.get_serializer_context)()) return await sync_to_async(serializer_class)(*args, **kwargs) async def get_serializer_class(self): """ Return the class to use for the serializer. Defaults to using `self.serializer_class`. You may want to override this if you need to provide different serializations depending on the incoming request. (Eg. admins get full serialization, others get basic serialization) """ assert self.serializer_class is not None, ( "'%s' should either include a `serializer_class` attribute, " "or override the `get_serializer_class()` method." % self.__class__.__name__ ) return self.serializer_class async def get_paginated_response(self, data): """ Return a paginated style `Response` object for the given output data. """ assert self.paginator is not None return await self.paginator.get_paginated_response(data) async def filter_queryset(self, queryset): """ Given a queryset, filter it with whichever filter backend is in use. You are unlikely to want to override this method, although you may need to call it either from a list view, or from a custom `get_object` method if you want to apply the configured filtering backend to the default queryset. """ for backend in list(self.filter_backends): queryset = await backend().filter_queryset(self.request, queryset, self) if inspect.iscoroutine(queryset): return await queryset return queryset# Concrete view classes that provide method handlers# by composing the mixin classes with the base view.class AsyncCreateAPIView(mixins.AsyncCreateModelMixin, AsyncGenericAPIView): """ Concrete view for creating a model instance. """ async def post(self, request, *args, **kwargs): return await self.create(request, *args, **kwargs)class AsyncListAPIView(mixins.AsyncListModelMixin, AsyncGenericAPIView): """ Concrete view for listing a queryset. """ async def get(self, request, *args, **kwargs): return await self.list(request, *args, **kwargs)class AsyncRetrieveAPIView(mixins.AsyncRetrieveModelMixin, AsyncGenericAPIView): """ Concrete view for retrieving a model instance. """ async def get(self, request, *args, **kwargs): return await self.retrieve(request, *args, **kwargs)class AsyncDestroyAPIView(mixins.AsyncDestroyModelMixin, AsyncGenericAPIView): """ Concrete view for deleting a model instance. """ async def delete(self, request, *args, **kwargs): return await self.destroy(request, *args, **kwargs)class AsyncUpdateAPIView(mixins.AsyncUpdateModelMixin, AsyncGenericAPIView): """ Concrete view for updating a model instance. """ async def put(self, request, *args, **kwargs): return await self.update(request, *args, **kwargs) async def patch(self, request, *args, **kwargs): return await self.partial_update(request, *args, **kwargs)class AsyncListCreateAPIView(mixins.AsyncListModelMixin, mixins.AsyncCreateModelMixin, AsyncGenericAPIView): """ Concrete view for listing a queryset or creating a model instance. """ async def get(self, request, *args, **kwargs): return await self.list(request, *args, **kwargs) async def post(self, request, *args, **kwargs): return await self.create(request, *args, **kwargs)class AsyncRetrieveUpdateAPIView(mixins.AsyncRetrieveModelMixin, mixins.AsyncUpdateModelMixin, AsyncGenericAPIView): """ Concrete view for retrieving, updating a model instance. """ async def get(self, request, *args, **kwargs): return await self.retrieve(request, *args, **kwargs) async def put(self, request, *args, **kwargs): return await self.update(request, *args, **kwargs) async def patch(self, request, *args, **kwargs): return await self.partial_update(request, *args, **kwargs)class AsyncRetrieveDestroyAPIView(mixins.AsyncRetrieveModelMixin, mixins.AsyncDestroyModelMixin, AsyncGenericAPIView): """ Concrete view for retrieving or deleting a model instance. """ async def get(self, request, *args, **kwargs): return await self.retrieve(request, *args, **kwargs) async def delete(self, request, *args, **kwargs): return await self.destroy(request, *args, **kwargs)class AsyncRetrieveUpdateDestroyAPIView( mixins.AsyncRetrieveModelMixin, mixins.AsyncUpdateModelMixin, mixins.AsyncDestroyModelMixin, AsyncGenericAPIView): """ Concrete view for retrieving, updating or deleting a model instance. """ async def get(self, request, *args, **kwargs): return await self.retrieve(request, *args, **kwargs) async def put(self, request, *args, **kwargs): return await self.update(request, *args, **kwargs) async def patch(self, request, *args, **kwargs): return await self.partial_update(request, *args, **kwargs) async def delete(self, request, *args, **kwargs): return await self.destroy(request, *args, **kwargs)mxins.py
from typing import Dictfrom asgiref.sync import sync_to_asyncfrom rest_framework import statusfrom rest_framework.mixins import ( CreateModelMixin, DestroyModelMixin, ListModelMixin, RetrieveModelMixin, UpdateModelMixin,)from rest_framework.response import Responsefrom rest_framework.settings import api_settingsclass AsyncCreateModelMixin(CreateModelMixin): """Make `create()` and `perform_create()` overridable. Without inheriting this class, the event loop can't be used in these two methods when override them. This must be inherited before `CreateModelMixin`. class MyViewSet(AsyncMixin, GenericViewSet, AsyncCreateModelMixin, CreateModelMixin): pass """ async def create(self, request, *args, **kwargs): serializer = await self.get_serializer(data=request.data) await sync_to_async(serializer.is_valid)(raise_exception=True) # MODIFIED HERE await self.perform_create(serializer) # MODIFIED HERE headers = await self.get_success_headers(serializer.data) return Response(serializer.data, status=status.HTTP_201_CREATED, headers=headers) async def perform_create(self, serializer): await sync_to_async(serializer.save)() async def get_success_headers(self, data) -> Dict: try: return {"Location": str(data[api_settings.URL_FIELD_NAME])} except (TypeError, KeyError): return {}class AsyncListModelMixin(ListModelMixin): async def list(self, request, *args, **kwargs): queryset = await self.filter_queryset(await self.get_queryset()) # queryset = await sync_to_async(queryset)() page = await self.paginate_queryset(queryset) if page is not None: serializer = await self.get_serializer(page, many=True) return await self.get_paginated_response(serializer.data) serializer = await self.get_serializer(queryset, many=True) return Response(serializer.data)class AsyncRetrieveModelMixin(RetrieveModelMixin): """ Retrieve a model instance. """ async def retrieve(self, request, *args, **kwargs): instance = await self.get_object() serializer = await self.get_serializer(instance) return Response(serializer.data)class AsyncUpdateModelMixin(UpdateModelMixin): """ Update a model instance. """ async def update(self, request, *args, **kwargs): partial = kwargs.pop("partial", False) instance = await self.get_object() serializer = await self.get_serializer(instance, data=request.data, partial=partial) await sync_to_async(serializer.is_valid)(raise_exception=True) await self.perform_update(serializer) if getattr(instance, "_prefetched_objects_cache", None): # If 'prefetch_related' has been applied to a queryset, we need to # forcibly invalidate the prefetch cache on the instance. instance._prefetched_objects_cache = {} return Response(serializer.data) async def perform_update(self, serializer): await sync_to_async(serializer.save)() async def partial_update(self, request, *args, **kwargs): kwargs["partial"] = True return await self.update(request, *args, **kwargs)class AsyncDestroyModelMixin(DestroyModelMixin): """Make `destroy()` and `perform_destroy()` overridable. Without inheriting this class, the event loop can't be used in these two methods when override them. This must be inherited before `DestroyModelMixin`. class MyViewSet(AsyncMixin, GenericViewSet, AsyncDestroyModelMixin, DestroyModelMixin): pass """ async def destroy(self, request, *args, **kwargs): instance = await self.get_object() # MODIFIED HERE await self.perform_destroy(instance) # MODIFIED HERE return Response(status=status.HTTP_204_NO_CONTENT) async def perform_destroy(self, instance): await sync_to_async(instance.delete)()应用
class ProFileUserViewList(AsyncGenericAPIView): queryset = ProfileUser.objects.all() def get_serializer_class(self): if self.request.method == "GET": return ProfileUserListSerializer async def get(self, request): """ 用户列表 :return: """ 结语
- 这只是实现视图异步， 还短少filter，page，swagger等调用异步
- 方才还看一下github的issues 想要rest反对异步还要不少工夫，毕竟django从3.0到4.0也是通过5年
- 借用github issues一句话，Async IO doesn't necessarily speeds up your code, it just reduces the server resources usage for concurrent tasks by leveraging concurrent network IO in a single-threaded application.
- 以上只是集体钻研源码批改实现，我用的数据库是tortoise，但在django4.0上应用也是没有问题