Link-Sortener/app/database_cleaner.py

import time
from apscheduler.schedulers.background import BackgroundScheduler
import atexit
from datetime import datetime

from app import app, db
from app.models import Url

def remove_dead_urls():
    for url in Url.query.all():
        check_url(url)

def check_url(url):
    if url.death is not None:
        if datetime.now() > url.death :
            app.logger.info(f"Removed hash '{url.hash}' because its retention time has passed.")
            db.session.delete(url)
            db.session.commit()
            return "Timeout"
    if url.view_counter is not None:
        if url.view_counter <= 0:
            app.logger.info(f"Removed hash '{url.hash}' because its viewcouner has run out.")
            db.session.delete(url)
            db.session.commit()
            return "Counter"
    return None

scheduler = None

def start_scheduler():
    global scheduler
    if scheduler is not None:
        app.logger.info("Database_cleaner scheduler was already started, not launching a second instane.")
        return
    scheduler = BackgroundScheduler()
    scheduler.add_job(func=remove_dead_urls, trigger="interval", hours=1)
    scheduler.start()
    app.logger.info("Database_cleaner scheduler was started.")

    # Shut down the scheduler when exiting the app
    atexit.register(shutdown_scheduler)

def shutdown_scheduler():
    scheduler.shutdown()
    app.logger.info("Database_cleaner scheduler was shut down.")