I recently did a parallel threading operation with my own website in Flask. So I completely understand your confusion, though I'm going to explain this the best of my abilities.
When creating parallel operations, it's best to use multi-threading. Basically multi-threading is meant for splitting operations up and doing them simultaneously on the CPU. Though this must be supported by the CPU, which most by today are supporting Multi-Threading.
Anyways, with the application. I initialized the Flask Application classes to share the data between all the threads, by using the main thread as the memory handler. Afterwards, I created the pages. Then within the initialization 'if statement'(if __name__ == '__main__') - Known as a driver class in other languages. I initialized and started the threads to do there parts of the application.
Notes:
Flask doesn't allow debug mode to be executed while not on the Main Thread. Basically meaning you cannot use the multi-threading on the Flask Apps when debugging the application, which is no problem. VSCode has a great output console to give me enough information to figure out the issues within the application. Though... sometimes thread error finding can be.. painful at times, it's best to watch your steps when debugging.
Another thing is you can still operate the threaded feature on Flask. Which I like to use on any Flask Application I make, because it allows better connection for the clients. For example, thread is disabled; the client connects and holds up the main thread, which holds it for a millisecond then releases it. Having threaded enabled; allows the clients to open and release multiple requests. Instead of all the clients piping through one thread.
Why would that be important? Well, if a client runs a heavy script that has to do operations on the local host machine, then that page's request query will be taking a larger amount of time. In returns, makes the client hold that main thread pipe, so therefore no-one else could connect.
My Code for your Issue:
import threading
from flask import Flask
# My typical setup for a Flask App.
# ./media is a folder that holds my JS, Imgs, CSS, etc.
app1 = Flask(__name__, static_folder='./media')
app2 = Flask(__name__, static_folder='./media')
@app1.route('/')
def index1():
return 'Hello World 1'
@app2.route('/')
def index2():
return 'Hello World 2'
# With Multi-Threading Apps, YOU CANNOT USE DEBUG!
# Though you can sub-thread.
def runFlaskApp1():
app1.run(host='127.0.0.1', port=5000, debug=False, threaded=True)
def runFlaskApp2():
app2.run(host='127.0.0.1', port=5001, debug=False, threaded=True)
if __name__ == '__main__':
# Executing the Threads seperatly.
t1 = threading.Thread(target=runFlaskApp1)
t2 = threading.Thread(target=runFlaskApp2)
t1.start()
t2.start()
PS: Run this app by doing python app.py instead of
export FLASK_APP=app.py
flask run --host 0.0.0.0 --port 5000
Hope this helps you, and happy developing!
