Use Flask current_app.logger inside threading
<p>I am using <code>current_app.logger</code> and when I tried to log inside thread it says "working outside of application context". How do I log a message from a method running in a thread?</p>

<pre><code>def background():
    current_app.logger.debug('logged from thread')

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



<pre><code>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 -
</code></pre>