Add eventlet db_pool use for mysql

This adds the use of eventlet's db_pool module so that we can make mysql
calls without blocking the whole process.

New config options are introduced:

sql_dbpool_enable -- Enables the use of eventlet's db_pool
sql_min_pool_size -- Set the minimum number of SQL connections

The default for sql_dbpool_enable is False for now, so there is
no forced behavior changes for those using mysql.  sql_min_pool_size
is defaulted to 1 to match behavior if not using db_pool.

Adds a new test module for our sqlalchemy code, testing this new option
as much as is possible without requiring mysql server to be running.

DocImpact

Change-Id: I99833f447df05c1beba5a3925b201dfccca72cae

1 files changed, 66 insertions, 0 deletions

diff --git a/nova/tests/test_sqlalchemy.py b/nova/tests/test_sqlalchemy.py
new file mode 100644
index 000000000..f79d607f8
--- /dev/null
+++ b/nova/tests/test_sqlalchemy.py
@@ -0,0 +1,66 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+# Copyright (c) 2012 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 SQLAlchemy specific code."""
+
+from eventlet import db_pool
+try:
+    import MySQLdb
+except ImportError:
+    MySQLdb = None
+
+from nova import context
+from nova.db.sqlalchemy import session
+from nova import test
+
+
+class DbPoolTestCase(test.TestCase):
+    def setUp(self):
+        super(DbPoolTestCase, self).setUp()
+        self.flags(sql_dbpool_enable=True)
+        self.user_id = 'fake'
+        self.project_id = 'fake'
+        self.context = context.RequestContext(self.user_id, self.project_id)
+        if not MySQLdb:
+            self.skipTest("Unable to test due to lack of MySQLdb")
+
+    def test_db_pool_option(self):
+        self.flags(sql_idle_timeout=11, sql_min_pool_size=21,
+                sql_max_pool_size=42)
+
+        info = {}
+
+        class FakeConnectionPool(db_pool.ConnectionPool):
+            def __init__(self, mod_name, **kwargs):
+                info['module'] = mod_name
+                info['kwargs'] = kwargs
+                super(FakeConnectionPool, self).__init__(mod_name,
+                        **kwargs)
+
+            def connect(self, *args, **kwargs):
+                raise test.TestingException()
+
+        self.stubs.Set(db_pool, 'ConnectionPool',
+                FakeConnectionPool)
+
+        sql_connection = 'mysql://user:pass@127.0.0.1/nova'
+        self.assertRaises(test.TestingException, session.create_engine,
+                sql_connection)
+
+        self.assertEqual(info['module'], MySQLdb)
+        self.assertEqual(info['kwargs']['max_idle'], 11)
+        self.assertEqual(info['kwargs']['min_size'], 21)
+        self.assertEqual(info['kwargs']['max_size'], 42)