如何让 Python FastAPI 异步/等待功能正常工作？

Posted 2023-03-30

【中文标题】如何让 Python FastAPI 异步/等待功能正常工作？

【英文标题】：How to get Python FastAPI async/await functionality to work properly?

【发布时间】：2020-04-20 06:43:59

【问题描述】：

如何正确利用 FastAPI 路由中的异步功能？

以下代码 sn-p 需要 10 秒来完成对我的 /home 路由的调用，而我预计只需要 5 秒。

from fastapi import FastAPI
import time

app = FastAPI()

async def my_func_1():
    """
    my func 1
    """
    print('Func1 started..!!')
    time.sleep(5)
    print('Func1 ended..!!')

    return 'a..!!'

async def my_func_2():
    """
    my func 2
    """
    print('Func2 started..!!')
    time.sleep(5)
    print('Func2 ended..!!')

    return 'b..!!'

@app.get("/home")
async def root():
    """
    my home route
    """
    start = time.time()
    a = await my_func_1()
    b = await my_func_2()
    end = time.time()
    print('It took  seconds to finish execution.'.format(round(end-start)))

    return 
        'a': a,
        'b': b
    

我得到以下结果，看起来是非异步的：

λ uvicorn fapi_test:app --reload
INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO:     Started reloader process [5116]
INFO:     Started server process [7780]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     127.0.0.1:51862 - "GET / HTTP/1.1" 404
Func1 started..!!
Func1 ended..!!
Func2 started..!!
Func2 ended..!!
It took 10 seconds to finish execution.
INFO:     127.0.0.1:51868 - "GET /home HTTP/1.1" 200

但是，我希望 FastAPI 打印如下：

Func1 started..!!
Func2 started..!!
Func1 ended..!!
Func2 ended..!!
It took 5 seconds to finish execution.

如果我做错了什么请纠正我？

【问题讨论】：

see

【参考方案1】：

time.sleep 被阻塞，你应该使用asyncio.sleep，还有.gather 和.wait 来聚合作业。这在Python 和FastAPI 中有详细记录。

【参考方案2】：

可能有点晚了，从上面的Hedde's response 详细说明，这是您的代码应用程序的外观。 请记住在睡觉时await，并收集等待对象 - 如果您不这样做，无论您使用time.sleep() 还是asyncio.sleep()，您都将不会让这两个任务同时运行。

from fastapi import FastAPI
import time
import asyncio

app = FastAPI()

async def my_func_1():
    """
    my func 1
    """
    print('Func1 started..!!')
    await asyncio.sleep(5)
    print('Func1 ended..!!')

    return 'a..!!'

async def my_func_2():
    """
    my func 2
    """
    print('Func2 started..!!')
    await asyncio.sleep(5)
    print('Func2 ended..!!')

    return 'b..!!'

@app.get("/home")
async def root():
    """
    my home route
    """
    start = time.time()
    futures = [my_func_1(), my_func_2()]
    a,b = await asyncio.gather(*futures)
    end = time.time()
    print('It took  seconds to finish execution.'.format(round(end-start)))

    return 
        'a': a,
        'b': b