Option to use one database when xdist plugin is used

pytest_django/fixtures.py

@@ -28,6 +28,11 @@ 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):
+        with _django_cursor_wrapper:
+            _setup_reused_databases()
+        return
+
     from .compat import setup_databases, teardown_databases
 
     # xdist
@@ -43,18 +48,11 @@ def _django_db_setup(request,
     if request.config.getvalue('nomigrations'):
         _disable_native_migrations()
 
-    db_args = {}
     with _django_cursor_wrapper:
-        if (request.config.getvalue('reuse_db') and
-                not request.config.getvalue('create_db')):
-            if get_django_version() >= (1, 8):
-                db_args['keepdb'] = True
-            else:
-                monkey_patch_creation_for_db_reuse()
-
-        # Create the database
-        db_cfg = setup_databases(verbosity=pytest.config.option.verbose,
-                                 interactive=False, **db_args)
+        if request.config.getvalue('reuse_db') and not request.config.getvalue('create_db'):
+            db_cfg = _setup_reused_databases()
+        else:
+            db_cfg = setup_databases(verbosity=pytest.config.option.verbose, interactive=False,)
 
     def teardown_database():
         with _django_cursor_wrapper:
@@ -64,6 +62,29 @@ def teardown_database():
         request.addfinalizer(teardown_database)
 
 
+def _setup_reused_databases():
+    from .compat import setup_databases
+    db_args = {}
+
+    if get_django_version() >= (1, 8):
+        db_args['keepdb'] = True
+    else:
+        monkey_patch_creation_for_db_reuse()
+
+    return setup_databases(verbosity=pytest.config.option.verbose, interactive=False, **db_args)
+
+
+def _is_xdist_one_db_enabled(config):
+    from django.conf import settings
+    is_sqlite = (settings.DATABASES['default']['ENGINE'] == 'django.db.backends.sqlite3')
+
+    one_db = config.getvalue('xdist_one_db')
+    if one_db and is_sqlite:
+        raise ValueError("xdist-one-db option can not be used together with sqlite3 backend")
+
+    return one_db
+
+
 def _django_db_fixture_helper(transactional, request, _django_cursor_wrapper):
     if is_django_unittest(request):
         return

pytest_django/plugin.py

@@ -14,12 +14,13 @@
 import py
 import pytest
 
+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 +45,10 @@ 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 +251,32 @@ 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()
+
+    from django.test.runner import setup_databases
+    # 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,

pytest_django_test/db_helpers.py

@@ -48,6 +48,13 @@ def run_mysql(*args):
     return run_cmd(*args)
 
 
+def skip_if_sqlite():
+    from django.conf import settings
+
+    if settings.DATABASES['default']['ENGINE'] == 'django.db.backends.sqlite3':
+        pytest.skip('Skip if sqlite3 backend')
+
+
 def skip_if_sqlite_in_memory():
     from django.conf import settings
 

tests/test_db_setup.py

@@ -5,7 +5,8 @@
 from pytest_django.lazy_django import get_django_version
 from pytest_django_test.db_helpers import (db_exists, drop_database,
                                            mark_database, mark_exists,
-                                           skip_if_sqlite_in_memory)
+                                           skip_if_sqlite_in_memory,
+                                           skip_if_sqlite)
 
 skip_on_python32 = pytest.mark.skipif(sys.version_info[:2] == (3, 2),
                                       reason='xdist is flaky with Python 3.2')
@@ -190,6 +191,41 @@ def test_d(settings):
     result.stdout.fnmatch_lines(['*PASSED*test_d*'])
 
 
+@skip_on_python32
+def test_xdist_one_db(django_testdir):
+    skip_if_sqlite()
+
+    drop_database('gw0')
+    drop_database('gw1')
+
+    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 'gw' not in db_name
+
+        @pytest.mark.django_db
+        def test_a(settings):
+            _check(settings)
+
+        @pytest.mark.django_db
+        def test_b(settings):
+            _check(settings)
+
+    ''')
+
+    result = django_testdir.runpytest_subprocess('-vv', '-n2', '-s', '--xdist-one-db')
+    assert result.ret == 0
+    result.stdout.fnmatch_lines(['*PASSED*test_a*'])
+    result.stdout.fnmatch_lines(['*PASSED*test_b*'])
+
+    assert db_exists()
+
+
 class TestSqliteWithXdist:
 
     pytestmark = skip_on_python32
@@ -217,6 +253,20 @@ def test_a():
         assert result.ret == 0
         result.stdout.fnmatch_lines(['*PASSED*test_a*'])
 
+    def test_xdist_with_one_db_does_not_work_with_sqlite(self, django_testdir):
+        django_testdir.create_test_module('''
+            import pytest
+
+            @pytest.mark.django_db
+            def test_a(settings):
+                pass
+        ''')
+
+        result = django_testdir.runpytest_subprocess('-vv', '-n1', '-s', '--xdist-one-db')
+        assert result.ret == 1
+        result.stdout.fnmatch_lines(['*= 1 error*'])
+        result.stdout.fnmatch_lines(['*ValueError*'])
+
 
 @pytest.mark.skipif(get_django_version() >= (1, 9),
                     reason=('Django 1.9 requires migration and has no concept '