7

我正在使用由 Uvicorn 服务器提供的 FastAPI 框架。我的应用程序应该在给定的端点 (/run) 上运行一些耗时的数值计算。为此，我使用了来自 fastAPI 的“background_task”（基本上是来自 Starlette 的“background_task”）。

运行应用程序时，经过一些名义行为后，服务器由于某种原因而关闭。

应用程序的日志如下所示：

INFO: Started server process [922]
INFO: Waiting for application startup.
DEBUG: None - ASGI [1] Started
DEBUG: None - ASGI [1] Sent {'type': 'lifespan.startup'}
DEBUG: None - ASGI [1] Received {'type': 'lifespan.startup.complete'}
INFO: Uvicorn running on http://0.0.0.0:8000 (Press CTRL+C to quit)
DEBUG: ('10.0.2.111', 57396) - Connected
DEBUG: ('10.0.2.111', 57397) - Connected
DEBUG: ('10.0.2.111', 57396) - ASGI [2] Started
DEBUG: ('10.0.2.111', 57396) - ASGI [2] Received {'type': 'http.response.start', 'status': 200, 'headers': '<...>'}
INFO: ('10.0.2.111', 57396) - "GET /run HTTP/1.1" 200
DEBUG: ('10.0.2.111', 57396) - ASGI [2] Received {'type': 'http.response.body', 'body': '<32 bytes>'}
DEBUG: ('10.0.2.111', 57396) - ASGI [3] Started
DEBUG: ('10.0.2.111', 57396) - ASGI [3] Received {'type': 'http.response.start', 'status': 404, 'headers': '<...>'}
INFO: ('10.0.2.111', 57396) - "GET /favicon.ico HTTP/1.1" 404
DEBUG: ('10.0.2.111', 57396) - ASGI [3] Received {'type': 'http.response.body', 'body': '<22 bytes>'}
DEBUG: ('10.0.2.111', 57396) - ASGI [3] Completed

...

DEBUG: ('10.0.2.111', 57396) - Disconnected
... The background task is completed.
DEBUG: ('10.0.2.111', 57396) - ASGI [2] Completed
DEBUG: ('10.0.2.111', 57397) - Disconnected
DEBUG: ('10.0.2.111', 57405) - Connected

...
The application goes on, with requests and completed background tasks.
At some point, during the execution of a background task:

INFO: Shutting down
DEBUG: ('10.0.2.111', 57568) - Disconnected
DEBUG: ('10.0.2.111', 57567) - Disconnected
INFO: Waiting for background tasks to complete. (CTRL+C to force quit)
DEBUG: ('10.0.2.111', 57567) - ASGI [6] Completed
INFO: Waiting for application shutdown.
DEBUG: None - ASGI [1] Sent {'type': 'lifespan.shutdown'}
DEBUG: None - ASGI [1] Received {'type': 'lifespan.shutdown.complete'}
DEBUG: None - ASGI [1] Completed
INFO: Finished server process [922]

我真的不明白为什么会这样。我不知道要尝试什么来修复它。

我的代码看起来像这样。

#!/usr/bin/env python3.7
import time
from fastapi import FastAPI, BackgroundTasks
import uvicorn
from starlette.responses import JSONResponse
import my_imports_from_project

analysis_api = FastAPI()

@analysis_api.get("/")
def root():
    return {"message": "root"}


@analysis_api.get("/test")
def test():
    return {"message": "test"}

@analysis_api.get("/run")
def run(name: str, background_task: BackgroundTasks):
    try:
        some_checks(name)
    except RaisedExceptions:
        body = {"running": False,
                "name": name,
                "cause": "Not found in database"}
        return JSONResponse(status_code=400, content=body)
    body = {"running": True,
            "name": name}
    background_task.add_task(run_analysis, name)
    return JSONResponse(status_code=200, content=body)


if __name__ == "__main__":
    uvicorn.run("api:analysis_api", host="0.0.0.0", log_level="debug")
4

1 回答 1

6

这就是我解决整个问题的方法。

我认为问题在于我的任务会产生一些进程以执行计算。所以，background_task我现在使用的是multiprocessing.Process(). 这解决了它。

正如来自 FastApi 的人所指出的，如果项目变得庞大而复杂，这个解决方案可能无法很好地扩展。在这种情况下，强烈建议使用消息队列+任务运行之类的东西（如FastApi 网站上所建议的那样。

但是，对于小型项目，使用multiprocessing.Processor的解决方案subprocess.Popen完全可以。

于 2019-07-17T09:46:47.593 回答