Fix unstable DB migration tests

Unit test 'test_walk_versions' in
'manila.tests.db.migrations.alembic.test_migration' module
takes abnormally very long time sometimes.
In common cases it takes about 5-10 seconds in CI for Mitaka set of
DB migrations.
In CI runs when this test fails, 'postgres' variant takes
about 47 seconds and mysql reaches common test timeout of 60 seconds.

Note, that this test becomes slower with each
addition of new DB migration. Also, 'pymysql' works much slower
on slow nodes than 'psycopg2'.

So, add new test decorator that sets individual test timeout.
And make it be 5 minutes for mentioned test. In worst case of Mitaka
DB migrations set it can take about 2 minutes, but make it bigger
to have a margin for future releases.

Change-Id: I233f96f29fe62231c2e7013b74c06396dd923f27
Closes-Bug: #1501272

manila/tests/db/migrations/alembic/test_migration.py

@@ -26,6 +26,7 @@ from sqlalchemy.sql import text
 
 from manila.db.migrations.alembic import migration
 from manila.tests.db.migrations.alembic import migrations_data_checks
+from manila.tests import utils as test_utils
 
 LOG = log.getLogger('manila.tests.test_migrations')
 
@@ -138,6 +139,13 @@ class ManilaMigrationsCheckers(test_migrations.WalkVersionsMixin,
                                         'exception': e})
             raise
 
+    # NOTE(vponomaryov): set 5 minutes timeout for case of running it on
+    # very slow nodes/VMs. Note, that this test becomes slower with each
+    # addition of new DB migration. On fast nodes it can take about 5-10 secs
+    # having Mitaka set of migrations.
+    # 'pymysql' works much slower on slow nodes than 'psycopg2'. And such
+    # timeout mostly required for testing of 'mysql' backend.
+    @test_utils.set_timeout(300)
     def test_walk_versions(self):
         """Walks all version scripts for each tested database.
 
@@ -163,6 +171,7 @@ class TestManilaMigrationsMySQL(ManilaMigrationsCheckers,
                                 test_base.MySQLOpportunisticTestCase):
     """Run migration tests on MySQL backend."""
 
+    @test_utils.set_timeout(300)
     def test_mysql_innodb(self):
         """Test that table creation on mysql only builds InnoDB tables."""
         with mock.patch('manila.db.sqlalchemy.api.get_engine',

manila/tests/utils.py

@@ -14,9 +14,11 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import fixtures
 import os
 
 from oslo_config import cfg
+import six
 
 from manila import context
 from manila import utils
@@ -35,6 +37,26 @@ def is_manila_installed():
         return False
 
 
+def set_timeout(timeout):
+    """Timeout decorator for unit test methods.
+
+    Use this decorator for tests that are expected to pass in very specific
+    amount of time, not common for all other tests.
+    It can have either big or small value.
+    """
+
+    def _decorator(f):
+
+        @six.wraps(f)
+        def _wrapper(self, *args, **kwargs):
+            self.useFixture(fixtures.Timeout(timeout, gentle=True))
+            return f(self, *args, **kwargs)
+
+        return _wrapper
+
+    return _decorator
+
+
 class create_temp_config_with_opts(object):
     """Creates temporary config file with provided opts and values.