text: #    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.
  
  from nova import context as nova_context
  from nova import test
  from nova.tests import fixtures as nova_fixtures
  from nova.tests.functional import fixtures as func_fixtures
  from nova.tests.functional import integrated_helpers
  from nova.tests.unit import policy_fixture
  
  
  class ServiceTestCase(test.TestCase,
                        integrated_helpers.InstanceHelperMixin):
      """Contains scenarios for testing services.
      """
  
      def setUp(self):
          super(ServiceTestCase, self).setUp()
          # Use the standard fixtures.
          self.useFixture(policy_fixture.RealPolicyFixture())
          self.useFixture(nova_fixtures.NeutronFixture(self))
          self.useFixture(nova_fixtures.GlanceFixture(self))
          self.useFixture(func_fixtures.PlacementFixture())
  
          # Start nova controller services.
          self.api = self.useFixture(nova_fixtures.OSAPIFixture(
              api_version='v2.1')).api
          self.start_service('conductor')
          self.scheduler = self.start_service('scheduler')
          # Our OSAPIFixture does not use a WSGIService, so just use the metadata
          # server fixture (which uses WSGIService) for testing.
          self.metadata = self.useFixture(
              nova_fixtures.OSMetadataServer()).metadata
          # Start one compute service.
          self.start_service('compute')
  
      def test_service_reset_resets_cell_cache(self):
          """Tests that the cell cache for database transaction context managers
          is cleared after a service reset (example scenario: SIGHUP).
          """
          server_req = self._build_server()
          server = self.api.post_server({'server': server_req})
          self._wait_for_state_change(server, 'ACTIVE')
          # Cell cache should be populated after creating a server.
          self.assertTrue(nova_context.CELL_CACHE)
          self.scheduler.reset()
          # Cell cache should be empty after the service reset.
          self.assertEqual({}, nova_context.CELL_CACHE)
  
          # Now test the WSGI service.
          server = self.api.post_server({'server': server_req})
          self._wait_for_state_change(server, 'ACTIVE')
          # Cell cache should be populated after creating a server.
          self.assertTrue(nova_context.CELL_CACHE)
          self.metadata.reset()
          # Cell cache should be empty after the service reset.
          self.assertEqual({}, nova_context.CELL_CACHE)
  
      def test_service_start_resets_cell_cache(self):
          """Tests that the cell cache for database transaction context managers
          is cleared upon a service start (example scenario: service start after
          a SIGTERM and the parent process forks child process workers).
          """
          server_req = self._build_server()
          server = self.api.post_server({'server': server_req})
          self._wait_for_state_change(server, 'ACTIVE')
          # Cell cache should be populated after creating a server.
          self.assertTrue(nova_context.CELL_CACHE)
          self.scheduler.stop()
          # NOTE(melwitt): Simulate a service starting after being stopped. The
          # scenario we want to handle is one where during start, the parent
          # process forks child process workers while one or more of its cached
          # database transaction context managers is inside a locked code
          # section. If the child processes are forked while the lock is locked,
          # the child processes begin with an already locked lock that can never
          # be acquired again. The result is that requests gets stuck and fail
          # with a CellTimeout error.
          self.scheduler.start()
          # Cell cache should be empty after the service start.
          self.assertEqual({}, nova_context.CELL_CACHE)
  
          # Now test the WSGI service.
          server = self.api.post_server({'server': server_req})
          self._wait_for_state_change(server, 'ACTIVE')
          # Cell cache should be populated after creating a server.
          self.assertTrue(nova_context.CELL_CACHE)
          self.metadata.stop()
          self.metadata.start()
          # Cell cache should be empty after the service reset.
          self.assertEqual({}, nova_context.CELL_CACHE)
  