Implemented basic sqlalchemy session class

taskflow/common/__init__.py

@@ -0,0 +1,19 @@
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
+#    Copyright (C) 2013 Rackspace Hosting Inc. 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.
+

taskflow/common/config.py

@@ -0,0 +1,49 @@
+# -*- coding: utf-8 -*-
+
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
+#    Copyright (C) 2013 Rackspace Hosting Inc. 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.
+
+"""
+Routines for configuring TaskFlow
+"""
+
+from oslo.config import cfg
+
+db_opts = [
+    cfg.StrOpt('sql_connection',
+               default='mysql://task:flow@localhost/taskflow',
+               help='The SQLAlchemy connection string used to connect to the '
+               'database'),
+    cfg.IntOpt('sql_idle_timeout',
+               default=3600,
+               help='timeout before idle sql connections are reaped')]
+
+celery_opts = [
+    cfg.StrOpt('celery_backend',
+               default='mysql://task:flow@localhost/taskflow',
+               help='The SQLAlchemy connection string used to connect to the '
+                    'celery backend'),
+    cfg.StrOpt('celery_MQ',
+               default='mongodb://task:flow@localhost:27017/taskflow',
+               help='The MongoDB connection string used to connect to the '
+                    'celery message queue')]
+
+def register_db_opts():
+    cfg.CONF.register_opts(db_opts)
+
+def register_celery_opts():
+    cfg.CONF.register_opts(celery_opts)

taskflow/db/sqlalchemy/api.py

@@ -16,3 +16,8 @@
 #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 #    License for the specific language governing permissions and limitations
 #    under the License.
+
+
+import logging
+
+LOG = logging.getLogger(__name__)

taskflow/db/sqlalchemy/session.py

@@ -16,3 +16,86 @@
 #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 #    License for the specific language governing permissions and limitations
 #    under the License.
+
+"""Session Handling for SQLAlchemy backend."""
+
+import logging
+import sqlalchemy
+
+from taskflow.db import api as db_api
+
+LOG = logging.getLogger(__name__)
+
+_ENGINE = None
+_MAKER = None
+
+
+def get_session(autocommit=True, expire_on_commit=True):
+    """Return a SQLAlchemy session."""
+    global _MAKER
+
+    if _MAKER is None:
+        _MAKER = get_maker(get_engine(), autocommit, expire_on_commit)
+    return _MAKER()
+
+
+def synchronous_switch_listener(dbapi_conn, connection_rec):
+    """Switch sqlite connections to non-synchronous mode"""
+    dbapi_conn.execute("PRAGMA synchronous = OFF")
+
+
+def ping_listener(dbapi_conn, connection_rec, connection_proxy):
+    """
+Ensures that MySQL connections checked out of the
+pool are alive.
+
+Borrowed from:
+http://groups.google.com/group/sqlalchemy/msg/a4ce563d802c929f
+"""
+    try:
+        dbapi_conn.cursor().execute('select 1')
+    except dbapi_conn.OperationalError, ex:
+        if ex.args[0] in (2006, 2013, 2014, 2045, 2055):
+            LOG.warn(_('Got mysql server has gone away: %s'), ex)
+            raise DisconnectionError("Database server went away")
+        else:
+            raise
+
+
+def get_engine():
+    """Return a SQLAlchemy engine."""
+    global _ENGINE
+    if _ENGINE is None:
+        connection_dict = sqlalchemy.engine.url.make_url(_get_sql_connection())
+        engine_args = {
+            "pool_recycle": _get_sql_idle_timeout(),
+            "echo": False,
+            "convert_unicode": True
+        }
+
+    if "sqlite" in connection_dict.drivername:
+        engine_args['poolclass'] = NullPool
+
+    if "mysql" in connection_dict.drivername:
+        engine_args['listeners'] = [MySQLPingListener()]
+
+    _ENGINE = sqlqlchemy.create_engine(_get_sql_connection(),
+                                       **engine_args)
+
+    #TODO: Check to make sure engine connected
+
+    return _ENGINE
+
+
+def get_maker(engine, autocommit=True, expire_on_commit=False):
+    "Return a SQLAlchemy sessionmaker using the given engine."""
+    return sqlalchemy.orm.sessionmaker(bind=engine,
+                                       autocommit=autocommit,
+                                       expire_on_commit=expire_on_commit)
+
+def _get_sql_connection():
+    return db_api.SQL_CONNECTION
+
+
+def _get_sql_idle_timeout():
+    return db_api.SQL_IDLE_TIMEOUT