Django access to database from another process

Question

I create a new Process from django app. Can i create new record in database from this process? My code throws exception:

django.core.exceptions.AppRegistryNotReady: Apps aren't loaded yet.

UPD_1

    def post(self, request):
       v = Value('b', True)
       proc = Process(target=start, args=(v, request.user, 
       request.data['stock'], request.data['pair'], '1111'))

       proc.start()

    def start(v, user, stock_exchange, pair, msg):
       MyModel.objects.create(user=user, stock_exchange=stock_exchange, pair=pair, date=datetime.now(), message=msg)

I guess yes if you’ve initialized it properly. Usually `manage.py` does all startup things but here you’ll need make them manually. — Eugene Lisitsky, Nov 08 '17 at 16:48

score 1 · Answer 1 · answered Nov 08 '17 at 17:07

You need to initialise the project first. You don't usually have to do this when going through manage.py, because it does it automatically, but a new process won't have had this done for it. So you need to put something like the following at the top of your code:

import django
import os
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "myproject.settings")
django.setup()

myproject.settings needs to be importable from whereever this code is running, so if not you might need to add to sys.path first.

Once this is done you can access your project's models, and use them to access your database, just like you normally would.

I starting a new proc from my view. After adding your code to top of proc func nothing happend — Theillko OSG, Nov 09 '17 at 09:11

DarkCygnus · Answer 2 · 2019-01-24T17:50:38.083

I was having a similar problem (also starting process from view), and what eventually helped me solve it was this answer.

The solution indicated is to close your DB connections just before you fork your new Process, so Django can recreate the connection when a query is needed in the new process. Adapted to you code it would be:

def post(self, request):
   v = Value('b', True)

   #close db connections here
   from django import db
   db.connections.close_all()

   #create and fork your process
   proc = Process(target=start, args=(v, request.user, 
   request.data['stock'], request.data['pair'], '1111'))

   proc.start()

Calling django.setup() did not help in my case, and after reading the linked answer, probably because forked processes already share the file descriptors, etc. of its parent process (so Django is already setup).

Django access to database from another process

2 Answers2