oslo.db/tests/test_api.py

# Copyright (c) 2013 Rackspace Hosting
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

"""Unit tests for DB API."""

import mock
from oslo.config import cfg

from oslo.db import api
from oslo.db import exception
from oslo.db.openstack.common import importutils
from tests import utils as test_utils

sqla = importutils.import_module('sqlalchemy')


def get_backend():
    return DBAPI()


class DBAPI(object):
    def _api_raise(self, *args, **kwargs):
        """Simulate raising a database-has-gone-away error

        This method creates a fake OperationalError with an ID matching
        a valid MySQL "database has gone away" situation. It also decrements
        the error_counter so that we can artificially keep track of
        how many times this function is called by the wrapper. When
        error_counter reaches zero, this function returns True, simulating
        the database becoming available again and the query succeeding.
        """

        if self.error_counter > 0:
            self.error_counter -= 1
            orig = sqla.exc.DBAPIError(False, False, False)
            orig.args = [2006, 'Test raise operational error']
            e = exception.DBConnectionError(orig)
            raise e
        else:
            return True

    def api_raise_default(self, *args, **kwargs):
        return self._api_raise(*args, **kwargs)

    @api.safe_for_db_retry
    def api_raise_enable_retry(self, *args, **kwargs):
        return self._api_raise(*args, **kwargs)

    def api_class_call1(_self, *args, **kwargs):
        return args, kwargs


class DBAPITestCase(test_utils.BaseTestCase):
    def test_dbapi_full_path_module_method(self):
        dbapi = api.DBAPI('tests.test_api')
        result = dbapi.api_class_call1(1, 2, kwarg1='meow')
        expected = ((1, 2), {'kwarg1': 'meow'})
        self.assertEqual(expected, result)

    def test_dbapi_unknown_invalid_backend(self):
        self.assertRaises(ImportError, api.DBAPI, 'tests.unit.db.not_existent')

    def test_dbapi_lazy_loading(self):
        dbapi = api.DBAPI('tests.test_api', lazy=True)

        self.assertIsNone(dbapi._backend)
        dbapi.api_class_call1(1, 'abc')
        self.assertIsNotNone(dbapi._backend)

    def test_dbapi_from_config(self):
        conf = cfg.ConfigOpts()

        dbapi = api.DBAPI.from_config(conf,
                                      backend_mapping={'sqlalchemy': __name__})
        self.assertIsNotNone(dbapi._backend)


class DBReconnectTestCase(DBAPITestCase):
    def setUp(self):
        super(DBReconnectTestCase, self).setUp()

        self.test_db_api = DBAPI()
        patcher = mock.patch(__name__ + '.get_backend',
                             return_value=self.test_db_api)
        patcher.start()
        self.addCleanup(patcher.stop)

    def test_raise_connection_error(self):
        self.dbapi = api.DBAPI('sqlalchemy', {'sqlalchemy': __name__})

        self.test_db_api.error_counter = 5
        self.assertRaises(exception.DBConnectionError, self.dbapi._api_raise)

    def test_raise_connection_error_decorated(self):
        self.dbapi = api.DBAPI('sqlalchemy', {'sqlalchemy': __name__})

        self.test_db_api.error_counter = 5
        self.assertRaises(exception.DBConnectionError,
                          self.dbapi.api_raise_enable_retry)
        self.assertEqual(4, self.test_db_api.error_counter, 'Unexpected retry')

    def test_raise_connection_error_enabled(self):
        self.dbapi = api.DBAPI('sqlalchemy',
                               {'sqlalchemy': __name__},
                               use_db_reconnect=True)

        self.test_db_api.error_counter = 5
        self.assertRaises(exception.DBConnectionError,
                          self.dbapi.api_raise_default)
        self.assertEqual(4, self.test_db_api.error_counter, 'Unexpected retry')

    def test_retry_one(self):
        self.dbapi = api.DBAPI('sqlalchemy',
                               {'sqlalchemy': __name__},
                               use_db_reconnect=True,
                               retry_interval=1)

        try:
            func = self.dbapi.api_raise_enable_retry
            self.test_db_api.error_counter = 1
            self.assertTrue(func(), 'Single retry did not succeed.')
        except Exception:
            self.fail('Single retry raised an un-wrapped error.')

        self.assertEqual(
            0, self.test_db_api.error_counter,
            'Counter not decremented, retry logic probably failed.')

    def test_retry_two(self):
        self.dbapi = api.DBAPI('sqlalchemy',
                               {'sqlalchemy': __name__},
                               use_db_reconnect=True,
                               retry_interval=1,
                               inc_retry_interval=False)

        try:
            func = self.dbapi.api_raise_enable_retry
            self.test_db_api.error_counter = 2
            self.assertTrue(func(), 'Multiple retry did not succeed.')
        except Exception:
            self.fail('Multiple retry raised an un-wrapped error.')

        self.assertEqual(
            0, self.test_db_api.error_counter,
            'Counter not decremented, retry logic probably failed.')

    def test_retry_until_failure(self):
        self.dbapi = api.DBAPI('sqlalchemy',
                               {'sqlalchemy': __name__},
                               use_db_reconnect=True,
                               retry_interval=1,
                               inc_retry_interval=False,
                               max_retries=3)

        func = self.dbapi.api_raise_enable_retry
        self.test_db_api.error_counter = 5
        self.assertRaises(
            exception.DBError, func,
            'Retry of permanent failure did not throw DBError exception.')

        self.assertNotEqual(
            0, self.test_db_api.error_counter,
            'Retry did not stop after sql_max_retries iterations.')