How to Maintain Unique Rserve Connections Per User Session in Flask?

Maintaining Unique Connections in Flask Sessions

Problem:
In a Flask application, the need arises to establish and maintain unique connections to a service (in this case, Rserve) for each user session. Storing the connection object in the session fails due to its non-JSON serializability, while using flask.g doesn't ensure persistence.

Solution:
To solve this issue, we separate the creation of Rserve connections from the user requests by employing a multiprocessing.Manager. This external process manages the connections for each user. Here's the code:

Separate Manager Process (rserve_manager.py):

import atexit
from multiprocessing import Lock
from multiprocessing.managers import BaseManager
import pyRserve

connections = {}
lock = Lock()


def get_connection(user_id):
    with lock:
        if user_id not in connections:
            connections[user_id] = pyRserve.connect()

        return connections[user_id]


@atexit.register
def close_connections():
    for connection in connections.values():
        connection.close()


manager = BaseManager(('', 37844), b'password')
manager.register('get_connection', get_connection)
server = manager.get_server()
server.serve_forever()

Accessing the Manager from the Flask Application:

from multiprocessing.managers import BaseManager
from flask import g, session

def get_rserve():
    if not hasattr(g, 'rserve'):
        manager = BaseManager(('', 37844), b'password')
        manager.register('get_connection')
        manager.connect()
        g.rserve = manager.get_connection(session['user_id'])

    return g.rserve

Usage in a View:

result = get_rserve().eval('3 + 5')

This approach provides unique connections per user, enabling the maintenance of session-specific data or service connections in Flask applications.

The above is the detailed content of How to Maintain Unique Rserve Connections Per User Session in Flask?. For more information, please follow other related articles on the PHP Chinese website!