python - 在线程中使用 Flask current_app.logger

Question

我正在使用 current_app.logger，当我尝试登录线程内部时，它显示“在应用程序上下文之外工作”。如何记录来自线程中运行的方法的消息？

def background():
    current_app.logger.debug('logged from thread')

@app.route('/')
def index():
    Thread(target=background).start()
    return 'Hello, World!'

Exception in thread Thread-16:
Traceback (most recent call last):
  File "/usr/lib64/python3.5/threading.py", line 914, in _bootstrap_inner
    self.run()
  File "/usr/lib64/python3.5/threading.py", line 862, in run
    self._target(*self._args, **self._kwargs)
  File "/home/sapam/demo.py", line 57, in background
    current_app.logger.critical('test')
  File "/home/sapam/.virtualenvs/demo/lib/python3.5/site-packages/werkzeug/local.py", line 343, in __getattr__
    return getattr(self._get_current_object(), name)
  File "/home/sapam/.virtualenvs/demo/lib/python3.5/site-packages/werkzeug/local.py", line 302, in _get_current_object
    return self.__local()
  File "/home/sapam/.virtualenvs/demo/lib/python3.5/site-packages/flask/globals.py", line 51, in _find_app
    raise RuntimeError(_app_ctx_err_msg)
RuntimeError: Working outside of application context.

This typically means that you attempted to use functionality that needed
to interface with the current application object in a way.  To solve
this set up an application context with app.app_context().  See the
documentation for more information.

127.0.0.1 - - [13/Sep/2016 12:28:24] "GET / HTTP/1.1" 200 -

Answer 1

您以标准方式使用标准logging 模块:获取当前模块的记录器并使用它记录一条消息。

def background():
    logging.getLogger(__name__).debug('logged from thread')

---

app.logger 主要用于内部 Flask 日志记录，或者至少在应用上下文中进行日志记录。如果您在一个线程中，您将不再处于相同的应用程序上下文中。

您可以将 current_app._get_current_object() 传递给线程并使用它代替 current_app。或者您可以子类化 Thread 来做类似的事情。

def background(app):
    app.logger.debug('logged from thread')

@app.route('/')
def index():
    Thread(target=background, kwargs={'app': current_app._get_current_object()}).start()
    return 'Hello, World!'

class FlaskThread(Thread):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.app = current_app._get_current_object()

    def run(self):
        with self.app.app_context():
            super().run()

def background():
    current_app.logger.debug('logged from thread')

@app.route('/')
def index():
    FlaskThread(target=background).start()
    return 'Hello, World!'

同样适用于多处理。