Option to use one database when xdist plugin is used

pytest_django/fixtures.py

@@ -28,6 +28,9 @@ def _django_db_setup(request,
     """Session-wide database setup, internal to pytest-django"""
     skip_if_no_django()
 
+    if is_xdist_one_db_enabled(request.config):
+        return
+
     from .compat import setup_databases, teardown_databases
 
     # xdist
@@ -64,6 +67,13 @@ def teardown_database():
         request.addfinalizer(teardown_database)
 
 
+def is_xdist_one_db_enabled(config):
+    from django.conf import settings
+    is_sqlite = (settings.DATABASES['default']['ENGINE'] == 'django.db.backends.sqlite3')
+    # can't use one sqlite3 db for distributed test run because of lock
+    return config.getvalue('xdist_one_db') and not is_sqlite
+
+
 def _django_db_fixture_helper(transactional, request, _django_cursor_wrapper):
     if is_django_unittest(request):
         return

pytest_django/plugin.py

@@ -13,13 +13,15 @@
 
 import py
 import pytest
+from django.test.runner import setup_databases
 
+from .db_reuse import monkey_patch_creation_for_db_reuse
 from .django_compat import is_django_unittest
 from .fixtures import (_django_db_setup, _live_server_helper, admin_client,
                        admin_user, client, db, django_user_model,
                        django_username_field, live_server, rf, settings,
-                       transactional_db)
-from .lazy_django import django_settings_is_configured, skip_if_no_django
+                       transactional_db, _handle_south, _disable_native_migrations)
+from .lazy_django import django_settings_is_configured, skip_if_no_django, get_django_version
 
 # Silence linters for imported fixtures.
 (_django_db_setup, _live_server_helper, admin_client, admin_user, client, db,
@@ -44,6 +46,10 @@ def pytest_addoption(parser):
                      action='store_true', dest='create_db', default=False,
                      help='Re-create the database, even if it exists. This '
                           'option will be ignored if not --reuse-db is given.')
+    group._addoption('--xdist-one-db',
+                     dest='xdist_one_db', default=False, action='store_true',
+                     help="Use only one database with xdist plugin. "
+                          "Doesn't work with sqlite3 backend due to db lock")
     group._addoption('--ds',
                      action='store', type='string', dest='ds', default=None,
                      help='Set DJANGO_SETTINGS_MODULE.')
@@ -246,6 +252,31 @@ def pytest_report_header(config):
         return [config._dsm_report_header]
 
 
+def pytest_xdist_setupnodes(config):
+    """called once before any remote node is set up. """
+    if not config.getvalue('xdist_one_db'):
+        return
+    _setup_django()
+
+    from django.conf import settings
+    if settings.DATABASES['default']['ENGINE'] == 'django.db.backends.sqlite3':
+        return
+
+    _handle_south()
+
+    if config.getvalue('nomigrations'):
+        _disable_native_migrations()
+
+    db_args = {}
+    if get_django_version() >= (1, 8):
+        db_args['keepdb'] = True
+    else:
+        monkey_patch_creation_for_db_reuse()
+
+    # Create the database
+    setup_databases(verbosity=config.option.verbose, interactive=False, **db_args)
+
+
 @pytest.mark.trylast
 def pytest_configure():
     # Allow Django settings to be configured in a user pytest_configure call,

tests/test_db_setup.py

@@ -190,6 +190,32 @@ def test_d(settings):
     result.stdout.fnmatch_lines(['*PASSED*test_d*'])
 
 
+def test_xdist_with_one_db_does_not_work_with_sqlite(django_testdir):
+    django_testdir.create_test_module('''
+        import pytest
+
+        from .app.models import Item
+
+        def _check(settings):
+            # Make sure that the database name looks correct
+            db_name = settings.DATABASES['default']['NAME']
+            assert db_name.endswith('_gw0')
+
+            assert Item.objects.count() == 0
+            Item.objects.create(name='foo')
+            assert Item.objects.count() == 1
+
+
+        @pytest.mark.django_db
+        def test_a(settings):
+            _check(settings)
+    ''')
+
+    result = django_testdir.runpytest_subprocess('-vv', '-n1', '-s', '--xdist-one-db')
+    assert result.ret == 0
+    result.stdout.fnmatch_lines(['*PASSED*test_a*'])
+
+
 class TestSqliteWithXdist:
 
     pytestmark = skip_on_python32