sync_to_async 装饰器，Django 中的异步视图

Question

我正在尝试按照视频教程并尝试理解 django 中的异步视图和 @sync_to_async 装饰器。

我有这个代码：

import time
import asyncio

from asgiref.sync import sync_to_async
from django.http import HttpResponse

from movies.models import Movie
from stories.models import Story



@sync_to_async
def get_movies_async():
    print('prepare to get the movies...')
    time.sleep(2)
    qs = Movie.objects.all()
    print('got all the movies')


@sync_to_async
def get_stories_async():
    print('prepare to get the stories...')
    time.sleep(5)
    qs = Story.objects.all()
    print('got all the stories')



async def main_view_async(request):
    start_time = time.time()
    await asyncio.gather(get_movies_async(), get_stories_async())
    total = (time.time() - start_time)
    print("total: ", total)
    return HttpResponse('async!')

但是当我从浏览器调用 main_view_async 时，仍然需要 7 秒，而不是像视频教程中那样需要 5 秒。
本教程可能已过时（2020 年）。或者也许我做错了什么？你能帮忙吗？

我的输出

prepare to get the movies...
got all the movies
prepare to get the stories...
got all the stories
total:  7.0126471519470215

教程终端输出

prepare to get the movies...
prepare to get the stories...
got all the movies
got all the stories
total:  5.0126471519470215

Answer 1

你是对的，它是因为教程是旧的。正如您在 Django 文档 中看到的，在 2020 年底

asgiref

发生了变化：

asgiref 3.3.0 版本更改了默认值 thread_sensitive 参数设置为 True。这是一个更安全的默认值，并且在 很多情况下与 Django 交互都是正确的值，但一定要 如果从之前的 asgiref 更新，则评估sync_to_async()的使用 版本。

这个默认的

thread_sensitive

值可以更改为

False

，但是，我不知道如何使用

@sync_to_async

装饰器来做到这一点，但它可以这样做：

# Change the function to a regular synchronous function
# (removed the decorator and changed the name to make it obvious it's not async)
# @sync_to_async
def get_movies():
    print('prepare to get the movies...')
    time.sleep(2)
    qs = Movie.objects.all()
    print('got all the movies')

# Do the same to this function as what was done to the above function
# @sync_to_async
def get_stories():
    print('prepare to get the stories...')
    time.sleep(5)
    qs = Story.objects.all()
    print('got all the stories')



async def main_view_async(request):
    start_time = time.time()
    
    # Create async functions from the synchronous functions
    # Set the thread_sensitive to False
    get_movies_async = sync_to_async(get_movies, thread_sensitive=False)
    get_stories_async = sync_to_async(get_stories, thread_sensitive=False)

    await asyncio.gather(get_movies_async(), get_stories_async())
    total = (time.time() - start_time)
    print("total: ", total)
    return HttpResponse('async!')