Flask app not updating fetched data from database without restart

Question

I'm having a problem with my Flask app where it doesn't update the data fetched from the database when I insert new data. The app only fetches the old data that was fetched when I started the app. No matter how much new data I insert, the fetched data doesn't update until I restart the Flask app by stopping it with ctrl+c and running it again with flask run. I tried disabling the cache like this:

cache = Cache(app, config={'CACHE_TYPE': 'null'})

However, it didn't work. I also checked the user class, the queries, and the functions, and everything seems to be working perfectly and showing results. Additionally, I'm using commit like this:

cursor.execute(query, data)
self.conn.commit()

**Here's my configuration: **

async_mode = None

app = Flask(__name__)

class MyApp:
    def __init__(self):
        self.app = app
        self.app.add_url_rule('/', 'home', self.home,
                              methods=["GET", "POST"])
        self.app.config['DEBUG'] = True
        # Secure session configuration
        self.app.config['SESSION_TYPE'] = 'filesystem'
        self.app.config['SESSION_FILE_DIR'] = '/tmp/flask_session'
        # Whether the session cookie should be secure (i.e., HTTPS only)
        self.app.config['SESSION_COOKIE_SECURE'] = True
        # Prevents JavaScript from accessing the session cookie
        self.app.config['SESSION_COOKIE_HTTPONLY'] = True
        self.app.config['SESSION_PERMANENT'] = False
        self.app.config['SESSION_COOKIE_SAMESITE'] = 'Strict'
        self.app.config['SECURITY_PASSWORD_SALT'] = 'password_salt'
        # 'development', 'production', or 'testing'
        self.app.config['ENV'] = 'development'
        # Disables testing
        self.app.config['TESTING'] = False
        self.app.config['SEND_FILE_MAX_AGE_DEFAULT'] = 0

    def run(self):
        self.app.run()

Is there any way to see the update without restarting the Flask app? Any help would be appreciated. Thanks in advance!

I tried disabling the cache like this:

cache = Cache(app, config={'CACHE_TYPE': 'null'})

However, it didn't work. I also checked the user class, the queries, and the functions, and everything seems to be working perfectly and showing results. Additionally, I'm using commit like this:

cursor.execute(query, data)
self.conn.commit()

fede · Accepted Answer · 2023-05-04 20:16:12Z

0

You have to use a task for get the database everytime. There is no event in flask (that i know) who change everytime you insert something in database. (if this is the problem, if not, could you be more specific?)

answered May 4, 2023 at 20:16

fede

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1 Comment

Mekkaoui_Redouane Over a year ago

Thanks for your response! Yes, that is the problem I'm facing. Can you explain how I can use a task or a background process to periodically update my app's data from the database? Also, is there a way to make Flask update the data every time new data is inserted into the database without having to restart the app? Any help would be greatly appreciated.

신준서 · Accepted Answer · 2024-03-25 16:07:19Z

You may not believe it, but insert a print() statement between the code that fetched data and the code that you use and put that data as a parameter.

I confirmed that the problem was solved by inserting the print() statement. *Even if it is not necessarily a print() statement, it will work the same way if you run a function that takes fetched data as a parameter and returns it as it is.

I don't know why it works, and I can't believe this phenomenon. But if you read this answer, please give it a try.

For your information, the code I used is as follows.

@celebration_blueprint.route('/celebration/add_form.html')
def celebration_add_form():
  users = user_service.get_all()
  print(users) #here
  return render_template('celebration_add.html', users=users)

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