[FIXED] Python Flask app is not running on heroku servers

Issue

I am trying to deploy my flask app on heroku but it shows a runtime error on the heroku server, but when i test it on my end, AKA localhost, it seems to work fine My Code:

import flask
from flask import request
from flask import jsonify
from GoogleNews import GoogleNews
from apscheduler.schedulers.background import BackgroundScheduler
import multiprocessing
googlenews = GoogleNews()
news_latest = []
googlenews.set_lang('en')
googlenews.set_period('1d')
googlenews.set_encode('utf-8')   
def get_latest_news():
    global news_latest
    googlenews.get_news('TECHNOLOGY')
    news_latest = googlenews.result()
my_scheduler = BackgroundScheduler()
my_scheduler.add_job(func=get_latest_news, trigger="interval", seconds=5)
my_scheduler.start()
app=flask.Flask(__name__)
@app.route('/', methods=["GET"])
def home():
    return jsonify(news_latest[0: 3])
app.run()

requirements.txt:

gunicorn
GoogleNews
APScheduler

PROCFILE:

web: gunicorn app:appweb: gunicorn app:app

runtime.txt:

python-3.9.4

But the server seems to crash when you open it, And what is remarkable is in the logs, Flask says it is running on a DEVELOPMENT server. It prints the location where it has started the app as 127.0.0.0.5000

Solution

I was able to overcome this problem, The right way of doing this is:

import flask
from flask import request
from flask import jsonify
from GoogleNews import GoogleNews
from apscheduler.schedulers.background import BackgroundScheduler
import multiprocessing
googlenews = GoogleNews()
news_latest = []
googlenews.set_lang('en')
googlenews.set_period('1d')
googlenews.set_encode('utf-8')   
def get_latest_news():
    global news_latest
    googlenews.get_news('TECHNOLOGY')
    news_latest = googlenews.result()
my_scheduler = BackgroundScheduler()
my_scheduler.add_job(func=get_latest_news, trigger="interval", seconds=5)
my_scheduler.start()
app=flask.Flask(__name__)
@app.route('/', methods=["GET"])
def home():
    return jsonify(news_latest[0: 3])

The change was to remove app.run() since heroku servers will already be running your code, if you put the app.run() heroku will consider this as default code and will run that too, hence the interpretation process will stop at app.run() and will never complete the interpretation. Hence the app will crash with no return response.

Answered By - Joel