当使用像 Uvicorn 这样的 ASGI 服务器时，Flask 记录器不起作用

Question

我想为我的 Flask 应用程序提供一个名为 Uvicorn 的 ASGI 服务器。结果当我将我的应用程序从 wsgi 转换为 asgi 时（按照此处的说明https://flask.palletsprojects.com/en/2.0.x/deploying/asgi/）突然 app.logger 函数未定义。但我确实需要日志功能来开发我的应用程序。

请按照以下步骤重现问题。

我写了这个基本的应用程序

from flask import Flask
from asgiref.wsgi import WsgiToAsgi

app = Flask(__name__)

@app.route("/")
def hello_world():
    app.logger.info("hey I am your favourite log message")
    return "<p>Hello, World!</p>"

app = WsgiToAsgi(app)

我安装了 uvicorn

pip install uvicorn

运行我的应用程序

uvicorn app:app

当应用尝试使用 app.logger 进行日志记录时，我收到此错误

ERROR:    Exception in ASGI application
Traceback (most recent call last):
  File "f:\projects\logger-flask\venv\lib\site-packages\uvicorn\protocols\http\h11_impl.py", line 373, in run_asgi
    result = await app(self.scope, self.receive, self.send)
  File "f:\projects\logger-flask\venv\lib\site-packages\uvicorn\middleware\proxy_headers.py", line 75, in __call__
    return await self.app(scope, receive, send)
  File "f:\projects\logger-flask\venv\lib\site-packages\asgiref\wsgi.py", line 21, in __call__
    await WsgiToAsgiInstance(self.wsgi_application)(scope, receive, send)
  File "f:\projects\logger-flask\venv\lib\site-packages\asgiref\wsgi.py", line 51, in __call__
    await self.run_wsgi_app(body)
  File "f:\projects\logger-flask\venv\lib\site-packages\asgiref\sync.py", line 444, in __call__
    ret = await asyncio.wait_for(future, timeout=None)
  File "C:\Users\Tamjid\AppData\Local\Programs\Python\Python38\lib\asyncio\tasks.py", line 455, in wait_for
    return await fut
  File "C:\Users\Tamjid\AppData\Local\Programs\Python\Python38\lib\concurrent\futures\thread.py", line 57, in run
    result = self.fn(*self.args, **self.kwargs)
  File "f:\projects\logger-flask\venv\lib\site-packages\asgiref\sync.py", line 486, in thread_handler
    return func(*args, **kwargs)
  File "f:\projects\logger-flask\venv\lib\site-packages\asgiref\wsgi.py", line 140, in run_wsgi_app
    for output in self.wsgi_application(environ, self.start_response):
  File "f:\projects\logger-flask\venv\lib\site-packages\flask\app.py", line 2088, in __call__
    return self.wsgi_app(environ, start_response)
  File "f:\projects\logger-flask\venv\lib\site-packages\flask\app.py", line 2073, in wsgi_app
    response = self.handle_exception(e)
  File "f:\projects\logger-flask\venv\lib\site-packages\flask\app.py", line 2070, in wsgi_app
    response = self.full_dispatch_request()
  File "f:\projects\logger-flask\venv\lib\site-packages\flask\app.py", line 1515, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "f:\projects\logger-flask\venv\lib\site-packages\flask\app.py", line 1513, in full_dispatch_request
    rv = self.dispatch_request()
  File "f:\projects\logger-flask\venv\lib\site-packages\flask\app.py", line 1499, in dispatch_request
    return self.ensure_sync(self.view_functions[rule.endpoint])(**req.view_args)
  File ".\app.py", line 8, in hello_world
    app.logger.info("hey I am your favourite log message")
AttributeError: 'WsgiToAsgi' object has no attribute 'logger'

Answer 1

Flask 的一个实例支持 WSGI 协议，并且它还增加了许多便利，例如记录器。如果你包装了 Flask 实例并失去了对它的引用，你就会失去那些方便的方法。

代替

app = WsgiToAsgi(app)

试试

wsgi = WsgiToAsgi(app)

然后

uvicorn app:wsgi

Answer 2

我为 WsgiToAsgi 实例使用了不同的名称，它删除了初始异常。但我仍然遇到日志记录错误。

--- Logging error ---
Traceback (most recent call last):
  File "C:\Users\Tamjid\AppData\Local\Programs\Python\Python38\lib\logging\__init__.py", line 1084, in emit       
    stream.write(msg + self.terminator)
TypeError: a bytes-like object is required, not 'str'

为了解决这个问题，我添加了这两行删除默认的日志记录处理程序

from flask.logging import default_handler
app.logger.removeHandler(default_handler)

我的完整工作代码在这里

from flask import Flask, current_app
from asgiref.wsgi import WsgiToAsgi
app = Flask(__name__)
from flask.logging import default_handler
app.logger.removeHandler(default_handler)

@app.route("/")
def hello_world():
    app.logger.warning('hey I am your favourite log message')
    return "<p>Hello, World!</p>"

wsgi = WsgiToAsgi(app)