[Python] Werkzeug BaseWSGIServer Thread Hangs after Handling Request. Terminal Unresponsive

This has stopped me from doing anything useful for more than a week - if you have experience with Python/Werkzeug/Flask/Multi-threading, please help...

Now, normally, you would run a Flask app in a separate terminal, via py flask.py, needing to manually spin it up and manually turn it off with Ctrl-C. My Python App only needs this local server in certain cases, for example: to get a token using Spotify's Authorization Code Flow so that I can later make valid requests using their Web API.

My auth_server.py file is the "section" responsible for all of this. Here lives a Class named LocalServerThread, that subclasses Thread, taken word-for-word from this answer. 8 years ago, this was the only useful answer for Windows in a sea of shit; alas, unfortunately, today it is only a partially-working example.

Here it is in it's full glory:

from werkzeug.serving import make_server

class ServerThread(threading.Thread):
THREAD_NAME = 'LocalServerThread'

def __init__(self, app):
threading.Thread.__init__(self, name=LocalServerThread.THREAD_NAME)
self.server = make_server('127.0.0.1', 8080, app)
self.ctx = app.app_context()
self.ctx.push()

def run(self):
log.info('starting server')
self.server.serve_forever()

def shutdown(self):
self.server.shutdown()

def start_server():
global server
app = flask.Flask('myapp')
# App routes defined here
server = ServerThread(app)
server.start()
log.info('server started')

def stop_server():
global server
server.shutdown()


Here is the rest of the code in question in my auth_server.py:

def start_local_http_server():
app = Flask(__name__)

@app.route('/')
def home():

@app.route('/login')
def login():

@app.route('/callback')
def callback():

global server
server = LocalServerThread(app)
server.start()
print(fr'Started {LocalServerThread.THREAD_NAME}, serving: http://127.0.0.1:8080')

def stop_local_http_server():
server.shutdown()


Here is my actual code from main.py that is leveraging this code:

if not auth_server.validate_token(reject=True):
auth_server.start_local_http_server()

time.sleep(4)

auth_server.stop_local_http_server()

print('Finally Done')


Now here is where it all Falls Apart...
I run it with py ./main.py. If I just let it run, shutdown will work perfectly, shutting everything down correctly. Good.
However, if, while the main thread sleeps in those 4 seconds, I go to any of the routes ('/', '/login', '/callback'), and the server successfully serves me the page, then when the program reaches self.server.shutdown(), it will just hang around there anywhere from 90-300 seconds before finally exiting and reaching print('Finally Done') back in the main thread. During this time, the terminal will look like this, refusing to let the program exit:

This is flippin' infuriating. I can't figure out what the heck is going in during debug as well. self.server.shutdown() goes deeper into socketserver.py BaseServer shutdown() method and I can't step into anything farther than the two lines within, like it's waiting around for something... But I got you the call stack:

These are the Call Stacks side by side, right before the debug loses track of what's going on.
First: Standard Run. ________________________ Second: going to '/' during the 4sec sleep:


Note: One more time, I am on Windows.
Is there anyone out there looking at this that has the knowledge/expertise to see the issue? This would really help not only me, but our posterity as well, I suspect...

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