Commit 10a16280 authored by Tim Graham's avatar Tim Graham
Browse files

Refs #24007 -- Removed an apps.populate() call in model unpickling that can cause deadlocks.

parent db9f21f0

django/db/models/base.py

+0 −2
Original line number Diff line number Diff line
@@ -1694,8 +1694,6 @@ def model_unpickle(model_id, attrs, factory): 
    Used to unpickle Model subclasses with deferred fields.

    """

    if isinstance(model_id, tuple):

        if not apps.ready:

            apps.populate(settings.INSTALLED_APPS)

        model = apps.get_model(*model_id)

    else:

        # Backwards compat - the model was cached directly in earlier versions.

docs/releases/1.10.txt

+10 −0
Original line number Diff line number Diff line
@@ -461,6 +461,16 @@ Since the introduction of migrations for the contrib apps in Django 1.8, the 
tables of these custom user test models were not created anymore making them

unusable in a testing context.



Apps registry is no longer auto-populated when unpickling models outside of Django

----------------------------------------------------------------------------------



The apps registry is no longer auto-populated when unpickling models. This was

added in Django 1.7.2 as an attempt to allow unpickling models outside of

Django, such as in an RQ worker, without calling ``django.setup()``, but it

creates the possibility of a deadlock. To adapt your code in the case of RQ,

you can `provide your own worker script <http://python-rq.org/docs/workers/>`_

that calls ``django.setup()``.



Miscellaneous

-------------

tests/model_regress/test_pickle.py

+1 −47
Original line number Diff line number Diff line 
import datetime

import os

import pickle

import subprocess

import sys



from django.core.files.temp import NamedTemporaryFile

from django.db import DJANGO_VERSION_PICKLE_KEY, models

from django.test import TestCase, mock

from django.utils._os import npath, upath

from django.test import TestCase

from django.utils.version import get_version



from .models import Article





class ModelPickleTestCase(TestCase):

    def test_missing_django_version_unpickling(self):
@@ -51,41 +43,3 @@ class ModelPickleTestCase(TestCase): 
        msg = "Pickled model instance's Django version 1.0 does not match the current version %s." % get_version()

        with self.assertRaisesMessage(RuntimeWarning, msg):

            pickle.loads(pickle.dumps(p))
 


    def test_unpickling_when_appregistrynotready(self):

        """

        #24007 -- Verifies that a pickled model can be unpickled without having

        to manually setup the apps registry beforehand.

        """

        script_template = """#!/usr/bin/env python

import pickle



from django.conf import settings



data = %r



settings.configure(DEBUG=False, INSTALLED_APPS=['model_regress'], SECRET_KEY = "blah")

article = pickle.loads(data)

print(article.headline)"""

        a = Article.objects.create(

            headline="Some object",

            pub_date=datetime.datetime.now(),

            article_text="This is an article",

        )



        with NamedTemporaryFile(mode='w+', suffix=".py") as script:

            script.write(script_template % pickle.dumps(a))

            script.flush()

            # A path to model_regress must be set in PYTHONPATH

            model_regress_dir = os.path.dirname(upath(__file__))

            model_regress_path = os.path.abspath(model_regress_dir)

            tests_path = os.path.split(model_regress_path)[0]

            pythonpath = os.environ.get('PYTHONPATH', '')

            pythonpath = npath(os.pathsep.join([tests_path, pythonpath]))



            with mock.patch.dict('os.environ', {'PYTHONPATH': pythonpath}):

                try:

                    result = subprocess.check_output([sys.executable, script.name])

                except subprocess.CalledProcessError:

                    self.fail("Unable to reload model pickled data")

        self.assertEqual(result.strip().decode(), "Some object")