listen to postgresql NOTIFY and launch arbitrary code

import importlib
import select
import json
import logging
from django.db import connection
from django.conf import settings
from django.core.management.base import BaseCommand

logger = logging.getLogger(__name__)


"""
Command used to listen for events in the database about badges
"""

class Command(BaseCommand):


    def handle(self, *args, **options):
        channels = settings.BADGES_CHANNEL
        cur = connection.cursor()
        for chan in channels:
            print chan
            cur.execute("LISTEN %s;" % chan)
        epoll = select.epoll()
        conn = connection.connection
        epoll.register(conn, select.EPOLLIN)
        while True:
            try:
                epoll.poll()
                conn.poll()
                while conn.notifies:
                    notify = conn.notifies.pop()
                    print notify
                    parse_payload(notify.payload)
            except BaseException as e:
                print e
                for chan in channels:
                    cur.execute("UNLISTEN %s;" % chan)
                break


def parse_payload(payload):
    """
    when a new message is posted by postgreSQL, we have to parse
    it.
    The message is a json payload with 2 mandatory keys: "module" and
    "function".
    And Two optional keys: args and kwargs
    """
    print payload
    try:
        callback = json.loads(payload)
    except Exception as e:
        logger.warning(e)
        return
    if not "module" in callback or not "function" in callback:
        logger.warning(
            "payload does not contains a 'module or function' key: %s"
            % payload)
        return
    try:
        mod = importlib.import_module(callback["module"])
        func = getattr(mod, callback["function"])
        results = func(*callback.get("args", []),
                       **callback.get("kwargs", {}))
        if results:
            print results
            logger.info(results)
    except Exception as e:
        print e