Add DB utils from Oslo

There is a lot of work done around DB and sqlalachemy in OSLO:

1) session and egnine wrappers
2) base models
3) tests for migration on real backends
4) exception wrappers
5) provide work around unqiue constraints
...

openstack-common.conf

@@ -3,6 +3,8 @@
 # The list of modules to copy from oslo-incubator.git
 module=cliutils
 module=config
+module=db
+module=db.sqlalchemy
 module=gettextutils
 module=importutils
 module=log

rally/openstack/common/db/__init__.py

@@ -0,0 +1,16 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2012 Cloudscaling Group, 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.

rally/openstack/common/db/api.py

@@ -0,0 +1,106 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# 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.
+
+"""Multiple DB API backend support.
+
+Supported configuration options:
+
+The following two parameters are in the 'database' group:
+`backend`: DB backend name or full module path to DB backend module.
+`use_tpool`: Enable thread pooling of DB API calls.
+
+A DB backend module should implement a method named 'get_backend' which
+takes no arguments.  The method can return any object that implements DB
+API methods.
+
+*NOTE*: There are bugs in eventlet when using tpool combined with
+threading locks. The python logging module happens to use such locks.  To
+work around this issue, be sure to specify thread=False with
+eventlet.monkey_patch().
+
+A bug for eventlet has been filed here:
+
+https://bitbucket.org/eventlet/eventlet/issue/137/
+"""
+import functools
+
+from oslo.config import cfg
+
+from rally.openstack.common import importutils
+from rally.openstack.common import lockutils
+
+
+db_opts = [
+    cfg.StrOpt('backend',
+               default='sqlalchemy',
+               deprecated_name='db_backend',
+               deprecated_group='DEFAULT',
+               help='The backend to use for db'),
+    cfg.BoolOpt('use_tpool',
+                default=False,
+                deprecated_name='dbapi_use_tpool',
+                deprecated_group='DEFAULT',
+                help='Enable the experimental use of thread pooling for '
+                     'all DB API calls')
+]
+
+CONF = cfg.CONF
+CONF.register_opts(db_opts, 'database')
+
+
+class DBAPI(object):
+    def __init__(self, backend_mapping=None):
+        if backend_mapping is None:
+            backend_mapping = {}
+        self.__backend = None
+        self.__backend_mapping = backend_mapping
+
+    @lockutils.synchronized('dbapi_backend', 'rally-')
+    def __get_backend(self):
+        """Get the actual backend.  May be a module or an instance of
+        a class.  Doesn't matter to us.  We do this synchronized as it's
+        possible multiple greenthreads started very quickly trying to do
+        DB calls and eventlet can switch threads before self.__backend gets
+        assigned.
+        """
+        if self.__backend:
+            # Another thread assigned it
+            return self.__backend
+        backend_name = CONF.database.backend
+        self.__use_tpool = CONF.database.use_tpool
+        if self.__use_tpool:
+            from eventlet import tpool
+            self.__tpool = tpool
+        # Import the untranslated name if we don't have a
+        # mapping.
+        backend_path = self.__backend_mapping.get(backend_name,
+                                                  backend_name)
+        backend_mod = importutils.import_module(backend_path)
+        self.__backend = backend_mod.get_backend()
+        return self.__backend
+
+    def __getattr__(self, key):
+        backend = self.__backend or self.__get_backend()
+        attr = getattr(backend, key)
+        if not self.__use_tpool or not hasattr(attr, '__call__'):
+            return attr
+
+        def tpool_wrapper(*args, **kwargs):
+            return self.__tpool.execute(attr, *args, **kwargs)
+
+        functools.update_wrapper(tpool_wrapper, attr)
+        return tpool_wrapper

rally/openstack/common/db/exception.py

@@ -0,0 +1,51 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2010 United States Government as represented by the
+# Administrator of the National Aeronautics and Space Administration.
+# 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.
+
+"""DB related custom exceptions."""
+
+from rally.openstack.common.gettextutils import _  # noqa
+
+
+class DBError(Exception):
+    """Wraps an implementation specific exception."""
+    def __init__(self, inner_exception=None):
+        self.inner_exception = inner_exception
+        super(DBError, self).__init__(str(inner_exception))
+
+
+class DBDuplicateEntry(DBError):
+    """Wraps an implementation specific exception."""
+    def __init__(self, columns=[], inner_exception=None):
+        self.columns = columns
+        super(DBDuplicateEntry, self).__init__(inner_exception)
+
+
+class DBDeadlock(DBError):
+    def __init__(self, inner_exception=None):
+        super(DBDeadlock, self).__init__(inner_exception)
+
+
+class DBInvalidUnicodeParameter(Exception):
+    message = _("Invalid Parameter: "
+                "Unicode is not supported by the current database.")
+
+
+class DbMigrationError(DBError):
+    """Wraps migration specific exception."""
+    def __init__(self, message=None):
+        super(DbMigrationError, self).__init__(str(message))

rally/openstack/common/db/sqlalchemy/__init__.py

@@ -0,0 +1,16 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2012 Cloudscaling Group, 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.

rally/openstack/common/db/sqlalchemy/migration.py

@@ -0,0 +1,278 @@
+# coding: utf-8
+#
+# Copyright (c) 2013 OpenStack Foundation
+# 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.
+#
+# Base on code in migrate/changeset/databases/sqlite.py which is under
+# the following license:
+#
+# The MIT License
+#
+# Copyright (c) 2009 Evan Rosson, Jan Dittberner, Domen Kožar
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
+
+import distutils.version as dist_version
+import os
+import re
+
+import migrate
+from migrate.changeset import ansisql
+from migrate.changeset.databases import sqlite
+from migrate.versioning import util as migrate_util
+import sqlalchemy
+from sqlalchemy.schema import UniqueConstraint
+
+from rally.openstack.common.db import exception
+from rally.openstack.common.db.sqlalchemy import session as db_session
+from rally.openstack.common.gettextutils import _  # noqa
+
+
+@migrate_util.decorator
+def patched_with_engine(f, *a, **kw):
+    url = a[0]
+    engine = migrate_util.construct_engine(url, **kw)
+
+    try:
+        kw['engine'] = engine
+        return f(*a, **kw)
+    finally:
+        if isinstance(engine, migrate_util.Engine) and engine is not url:
+            migrate_util.log.debug('Disposing SQLAlchemy engine %s', engine)
+            engine.dispose()
+
+
+# TODO(jkoelker) When migrate 0.7.3 is released and nova depends
+#                on that version or higher, this can be removed
+MIN_PKG_VERSION = dist_version.StrictVersion('0.7.3')
+if (not hasattr(migrate, '__version__') or
+        dist_version.StrictVersion(migrate.__version__) < MIN_PKG_VERSION):
+    migrate_util.with_engine = patched_with_engine
+
+
+# NOTE(jkoelker) Delay importing migrate until we are patched
+from migrate import exceptions as versioning_exceptions
+from migrate.versioning import api as versioning_api
+from migrate.versioning.repository import Repository
+
+_REPOSITORY = None
+
+get_engine = db_session.get_engine
+
+
+def _get_unique_constraints(self, table):
+    """Retrieve information about existing unique constraints of the table
+
+    This feature is needed for _recreate_table() to work properly.
+    Unfortunately, it's not available in sqlalchemy 0.7.x/0.8.x.
+
+    """
+
+    data = table.metadata.bind.execute(
+        """SELECT sql
+           FROM sqlite_master
+           WHERE
+               type='table' AND
+               name=:table_name""",
+        table_name=table.name
+    ).fetchone()[0]
+
+    UNIQUE_PATTERN = "CONSTRAINT (\w+) UNIQUE \(([^\)]+)\)"
+    return [
+        UniqueConstraint(
+            *[getattr(table.columns, c.strip(' "')) for c in cols.split(",")],
+            name=name
+        )
+        for name, cols in re.findall(UNIQUE_PATTERN, data)
+    ]
+
+
+def _recreate_table(self, table, column=None, delta=None, omit_uniques=None):
+    """Recreate the table properly
+
+    Unlike the corresponding original method of sqlalchemy-migrate this one
+    doesn't drop existing unique constraints when creating a new one.
+
+    """
+
+    table_name = self.preparer.format_table(table)
+
+    # we remove all indexes so as not to have
+    # problems during copy and re-create
+    for index in table.indexes:
+        index.drop()
+
+    # reflect existing unique constraints
+    for uc in self._get_unique_constraints(table):
+        table.append_constraint(uc)
+    # omit given unique constraints when creating a new table if required
+    table.constraints = set([
+        cons for cons in table.constraints
+        if omit_uniques is None or cons.name not in omit_uniques
+    ])
+
+    self.append('ALTER TABLE %s RENAME TO migration_tmp' % table_name)
+    self.execute()
+
+    insertion_string = self._modify_table(table, column, delta)
+
+    table.create(bind=self.connection)
+    self.append(insertion_string % {'table_name': table_name})
+    self.execute()
+    self.append('DROP TABLE migration_tmp')
+    self.execute()
+
+
+def _visit_migrate_unique_constraint(self, *p, **k):
+    """Drop the given unique constraint
+
+    The corresponding original method of sqlalchemy-migrate just
+    raises NotImplemented error
+
+    """
+
+    self.recreate_table(p[0].table, omit_uniques=[p[0].name])
+
+
+def patch_migrate():
+    """A workaround for SQLite's inability to alter things
+
+    SQLite abilities to alter tables are very limited (please read
+    http://www.sqlite.org/lang_altertable.html for more details).
+    E. g. one can't drop a column or a constraint in SQLite. The
+    workaround for this is to recreate the original table omitting
+    the corresponding constraint (or column).
+
+    sqlalchemy-migrate library has recreate_table() method that
+    implements this workaround, but it does it wrong:
+
+        - information about unique constraints of a table
+          is not retrieved. So if you have a table with one
+          unique constraint and a migration adding another one
+          you will end up with a table that has only the
+          latter unique constraint, and the former will be lost
+
+        - dropping of unique constraints is not supported at all
+
+    The proper way to fix this is to provide a pull-request to
+    sqlalchemy-migrate, but the project seems to be dead. So we
+    can go on with monkey-patching of the lib at least for now.
+
+    """
+
+    # this patch is needed to ensure that recreate_table() doesn't drop
+    # existing unique constraints of the table when creating a new one
+    helper_cls = sqlite.SQLiteHelper
+    helper_cls.recreate_table = _recreate_table
+    helper_cls._get_unique_constraints = _get_unique_constraints
+
+    # this patch is needed to be able to drop existing unique constraints
+    constraint_cls = sqlite.SQLiteConstraintDropper
+    constraint_cls.visit_migrate_unique_constraint = \
+        _visit_migrate_unique_constraint
+    constraint_cls.__bases__ = (ansisql.ANSIColumnDropper,
+                                sqlite.SQLiteConstraintGenerator)
+
+
+def db_sync(abs_path, version=None, init_version=0):
+    """Upgrade or downgrade a database.
+
+    Function runs the upgrade() or downgrade() functions in change scripts.
+
+    :param abs_path:     Absolute path to migrate repository.
+    :param version:      Database will upgrade/downgrade until this version.
+                         If None - database will update to the latest
+                         available version.
+    :param init_version: Initial database version
+    """
+    if version is not None:
+        try:
+            version = int(version)
+        except ValueError:
+            raise exception.DbMigrationError(
+                message=_("version should be an integer"))
+
+    current_version = db_version(abs_path, init_version)
+    repository = _find_migrate_repo(abs_path)
+    if version is None or version > current_version:
+        return versioning_api.upgrade(get_engine(), repository, version)
+    else:
+        return versioning_api.downgrade(get_engine(), repository,
+                                        version)
+
+
+def db_version(abs_path, init_version):
+    """Show the current version of the repository.
+
+    :param abs_path: Absolute path to migrate repository
+    :param version:  Initial database version
+    """
+    repository = _find_migrate_repo(abs_path)
+    try:
+        return versioning_api.db_version(get_engine(), repository)
+    except versioning_exceptions.DatabaseNotControlledError:
+        meta = sqlalchemy.MetaData()
+        engine = get_engine()
+        meta.reflect(bind=engine)
+        tables = meta.tables
+        if len(tables) == 0:
+            db_version_control(abs_path, init_version)
+            return versioning_api.db_version(get_engine(), repository)
+        else:
+            # Some pre-Essex DB's may not be version controlled.
+            # Require them to upgrade using Essex first.
+            raise exception.DbMigrationError(
+                message=_("Upgrade DB using Essex release first."))
+
+
+def db_version_control(abs_path, version=None):
+    """Mark a database as under this repository's version control.
+
+    Once a database is under version control, schema changes should
+    only be done via change scripts in this repository.
+
+    :param abs_path: Absolute path to migrate repository
+    :param version:  Initial database version
+    """
+    repository = _find_migrate_repo(abs_path)
+    versioning_api.version_control(get_engine(), repository, version)
+    return version
+
+
+def _find_migrate_repo(abs_path):
+    """Get the project's change script repository
+
+    :param abs_path: Absolute path to migrate repository
+    """
+    global _REPOSITORY
+    if not os.path.exists(abs_path):
+        raise exception.DbMigrationError("Path %s not found" % abs_path)
+    if _REPOSITORY is None:
+        _REPOSITORY = Repository(abs_path)
+    return _REPOSITORY

rally/openstack/common/db/sqlalchemy/models.py

@@ -0,0 +1,108 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright (c) 2011 X.commerce, a business unit of eBay Inc.
+# Copyright 2010 United States Government as represented by the
+# Administrator of the National Aeronautics and Space Administration.
+# Copyright 2011 Piston Cloud Computing, Inc.
+# Copyright 2012 Cloudscaling Group, 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.
+"""
+SQLAlchemy models.
+"""
+
+import six
+
+from sqlalchemy import Column, Integer
+from sqlalchemy import DateTime
+from sqlalchemy.orm import object_mapper
+
+from rally.openstack.common.db.sqlalchemy import session as sa
+from rally.openstack.common import timeutils
+
+
+class ModelBase(object):
+    """Base class for models."""
+    __table_initialized__ = False
+
+    def save(self, session=None):
+        """Save this object."""
+        if not session:
+            session = sa.get_session()
+        # NOTE(boris-42): This part of code should be look like:
+        #                       sesssion.add(self)
+        #                       session.flush()
+        #                 But there is a bug in sqlalchemy and eventlet that
+        #                 raises NoneType exception if there is no running
+        #                 transaction and rollback is called. As long as
+        #                 sqlalchemy has this bug we have to create transaction
+        #                 explicity.
+        with session.begin(subtransactions=True):
+            session.add(self)
+            session.flush()
+
+    def __setitem__(self, key, value):
+        setattr(self, key, value)
+
+    def __getitem__(self, key):
+        return getattr(self, key)
+
+    def get(self, key, default=None):
+        return getattr(self, key, default)
+
+    def __iter__(self):
+        columns = dict(object_mapper(self).columns).keys()
+        # NOTE(russellb): Allow models to specify other keys that can be looked
+        # up, beyond the actual db columns.  An example would be the 'name'
+        # property for an Instance.
+        if hasattr(self, '_extra_keys'):
+            columns.extend(self._extra_keys())
+        self._i = iter(columns)
+        return self
+
+    def next(self):
+        n = six.advance_iterator(self._i)
+        return n, getattr(self, n)
+
+    def update(self, values):
+        """Make the model object behave like a dict."""
+        for k, v in six.iteritems(values):
+            setattr(self, k, v)
+
+    def iteritems(self):
+        """Make the model object behave like a dict.
+
+        Includes attributes from joins.
+        """
+        local = dict(self)
+        joined = dict([(k, v) for k, v in six.iteritems(self.__dict__)
+                      if not k[0] == '_'])
+        local.update(joined)
+        return local.iteritems()
+
+
+class TimestampMixin(object):
+    created_at = Column(DateTime, default=timeutils.utcnow)
+    updated_at = Column(DateTime, onupdate=timeutils.utcnow)
+
+
+class SoftDeleteMixin(object):
+    deleted_at = Column(DateTime)
+    deleted = Column(Integer, default=0)
+
+    def soft_delete(self, session=None):
+        """Mark this object as deleted."""
+        self.deleted = self.id
+        self.deleted_at = timeutils.utcnow()
+        self.save(session=session)

rally/openstack/common/db/sqlalchemy/session.py

@@ -0,0 +1,793 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2010 United States Government as represented by the
+# Administrator of the National Aeronautics and Space Administration.
+# 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.
+
+"""Session Handling for SQLAlchemy backend.
+
+Initializing:
+
+* Call set_defaults with the minimal of the following kwargs:
+    sql_connection, sqlite_db
+
+  Example:
+
+    session.set_defaults(
+        sql_connection="sqlite:///var/lib/rally/sqlite.db",
+        sqlite_db="/var/lib/rally/sqlite.db")
+
+Recommended ways to use sessions within this framework:
+
+* Don't use them explicitly; this is like running with AUTOCOMMIT=1.
+  model_query() will implicitly use a session when called without one
+  supplied. This is the ideal situation because it will allow queries
+  to be automatically retried if the database connection is interrupted.
+
+    Note: Automatic retry will be enabled in a future patch.
+
+  It is generally fine to issue several queries in a row like this. Even though
+  they may be run in separate transactions and/or separate sessions, each one
+  will see the data from the prior calls. If needed, undo- or rollback-like
+  functionality should be handled at a logical level. For an example, look at
+  the code around quotas and reservation_rollback().
+
+  Examples:
+
+    def get_foo(context, foo):
+        return model_query(context, models.Foo).\
+                filter_by(foo=foo).\
+                first()
+
+    def update_foo(context, id, newfoo):
+        model_query(context, models.Foo).\
+                filter_by(id=id).\
+                update({'foo': newfoo})
+
+    def create_foo(context, values):
+        foo_ref = models.Foo()
+        foo_ref.update(values)
+        foo_ref.save()
+        return foo_ref
+
+
+* Within the scope of a single method, keeping all the reads and writes within
+  the context managed by a single session. In this way, the session's __exit__
+  handler will take care of calling flush() and commit() for you.
+  If using this approach, you should not explicitly call flush() or commit().
+  Any error within the context of the session will cause the session to emit
+  a ROLLBACK. If the connection is dropped before this is possible, the
+  database will implicitly rollback the transaction.
+
+     Note: statements in the session scope will not be automatically retried.
+
+  If you create models within the session, they need to be added, but you
+  do not need to call model.save()
+
+    def create_many_foo(context, foos):
+        session = get_session()
+        with session.begin():
+            for foo in foos:
+                foo_ref = models.Foo()
+                foo_ref.update(foo)
+                session.add(foo_ref)
+
+    def update_bar(context, foo_id, newbar):
+        session = get_session()
+        with session.begin():
+            foo_ref = model_query(context, models.Foo, session).\
+                        filter_by(id=foo_id).\
+                        first()
+            model_query(context, models.Bar, session).\
+                        filter_by(id=foo_ref['bar_id']).\
+                        update({'bar': newbar})
+
+  Note: update_bar is a trivially simple example of using "with session.begin".
+  Whereas create_many_foo is a good example of when a transaction is needed,
+  it is always best to use as few queries as possible. The two queries in
+  update_bar can be better expressed using a single query which avoids
+  the need for an explicit transaction. It can be expressed like so:
+
+    def update_bar(context, foo_id, newbar):
+        subq = model_query(context, models.Foo.id).\
+                filter_by(id=foo_id).\
+                limit(1).\
+                subquery()
+        model_query(context, models.Bar).\
+                filter_by(id=subq.as_scalar()).\
+                update({'bar': newbar})
+
+  For reference, this emits approximagely the following SQL statement:
+
+    UPDATE bar SET bar = ${newbar}
+        WHERE id=(SELECT bar_id FROM foo WHERE id = ${foo_id} LIMIT 1);
+
+* Passing an active session between methods. Sessions should only be passed
+  to private methods. The private method must use a subtransaction; otherwise
+  SQLAlchemy will throw an error when you call session.begin() on an existing
+  transaction. Public methods should not accept a session parameter and should
+  not be involved in sessions within the caller's scope.
+
+  Note that this incurs more overhead in SQLAlchemy than the above means
+  due to nesting transactions, and it is not possible to implicitly retry
+  failed database operations when using this approach.
+
+  This also makes code somewhat more difficult to read and debug, because a
+  single database transaction spans more than one method. Error handling
+  becomes less clear in this situation. When this is needed for code clarity,
+  it should be clearly documented.
+
+    def myfunc(foo):
+        session = get_session()
+        with session.begin():
+            # do some database things
+            bar = _private_func(foo, session)
+        return bar
+
+    def _private_func(foo, session=None):
+        if not session:
+            session = get_session()
+        with session.begin(subtransaction=True):
+            # do some other database things
+        return bar
+
+
+There are some things which it is best to avoid:
+
+* Don't keep a transaction open any longer than necessary.
+
+  This means that your "with session.begin()" block should be as short
+  as possible, while still containing all the related calls for that
+  transaction.
+
+* Avoid "with_lockmode('UPDATE')" when possible.
+
+  In MySQL/InnoDB, when a "SELECT ... FOR UPDATE" query does not match
+  any rows, it will take a gap-lock. This is a form of write-lock on the
+  "gap" where no rows exist, and prevents any other writes to that space.
+  This can effectively prevent any INSERT into a table by locking the gap
+  at the end of the index. Similar problems will occur if the SELECT FOR UPDATE
+  has an overly broad WHERE clause, or doesn't properly use an index.
+
+  One idea proposed at ODS Fall '12 was to use a normal SELECT to test the
+  number of rows matching a query, and if only one row is returned,
+  then issue the SELECT FOR UPDATE.
+
+  The better long-term solution is to use INSERT .. ON DUPLICATE KEY UPDATE.
+  However, this can not be done until the "deleted" columns are removed and
+  proper UNIQUE constraints are added to the tables.
+
+
+Enabling soft deletes:
+
+* To use/enable soft-deletes, the SoftDeleteMixin must be added
+  to your model class. For example:
+
+      class NovaBase(models.SoftDeleteMixin, models.ModelBase):
+          pass
+
+
+Efficient use of soft deletes:
+
+* There are two possible ways to mark a record as deleted:
+    model.soft_delete() and query.soft_delete().
+
+  model.soft_delete() method works with single already fetched entry.
+  query.soft_delete() makes only one db request for all entries that correspond
+  to query.
+
+* In almost all cases you should use query.soft_delete(). Some examples:
+
+        def soft_delete_bar():
+            count = model_query(BarModel).find(some_condition).soft_delete()
+            if count == 0:
+                raise Exception("0 entries were soft deleted")
+
+        def complex_soft_delete_with_synchronization_bar(session=None):
+            if session is None:
+                session = get_session()
+            with session.begin(subtransactions=True):
+                count = model_query(BarModel).\
+                            find(some_condition).\
+                            soft_delete(synchronize_session=True)
+                            # Here synchronize_session is required, because we
+                            # don't know what is going on in outer session.
+                if count == 0:
+                    raise Exception("0 entries were soft deleted")
+
+* There is only one situation where model.soft_delete() is appropriate: when
+  you fetch a single record, work with it, and mark it as deleted in the same
+  transaction.
+
+        def soft_delete_bar_model():
+            session = get_session()
+            with session.begin():
+                bar_ref = model_query(BarModel).find(some_condition).first()
+                # Work with bar_ref
+                bar_ref.soft_delete(session=session)
+
+  However, if you need to work with all entries that correspond to query and
+  then soft delete them you should use query.soft_delete() method:
+
+        def soft_delete_multi_models():
+            session = get_session()
+            with session.begin():
+                query = model_query(BarModel, session=session).\
+                            find(some_condition)
+                model_refs = query.all()
+                # Work with model_refs
+                query.soft_delete(synchronize_session=False)
+                # synchronize_session=False should be set if there is no outer
+                # session and these entries are not used after this.
+
+  When working with many rows, it is very important to use query.soft_delete,
+  which issues a single query. Using model.soft_delete(), as in the following
+  example, is very inefficient.
+
+        for bar_ref in bar_refs:
+            bar_ref.soft_delete(session=session)
+        # This will produce count(bar_refs) db requests.
+"""
+
+import functools
+import os.path
+import re
+import time
+
+from eventlet import greenthread
+from oslo.config import cfg
+import six
+from sqlalchemy import exc as sqla_exc
+import sqlalchemy.interfaces
+from sqlalchemy.interfaces import PoolListener
+import sqlalchemy.orm
+from sqlalchemy.pool import NullPool, StaticPool
+from sqlalchemy.sql.expression import literal_column
+
+from rally.openstack.common.db import exception
+from rally.openstack.common.gettextutils import _  # noqa
+from rally.openstack.common import log as logging
+from rally.openstack.common import timeutils
+
+sqlite_db_opts = [
+    cfg.StrOpt('sqlite_db',
+               default='rally.sqlite',
+               help='the filename to use with sqlite'),
+    cfg.BoolOpt('sqlite_synchronous',
+                default=True,
+                help='If true, use synchronous mode for sqlite'),
+]
+
+database_opts = [
+    cfg.StrOpt('connection',
+               default='sqlite:///' +
+                       os.path.abspath(os.path.join(os.path.dirname(__file__),
+                       '../', '$sqlite_db')),
+               help='The SQLAlchemy connection string used to connect to the '
+                    'database',
+               deprecated_opts=[cfg.DeprecatedOpt('sql_connection',
+                                                  group='DEFAULT'),
+                                cfg.DeprecatedOpt('sql_connection',
+                                                  group='DATABASE')]),
+    cfg.StrOpt('slave_connection',
+               default='',
+               help='The SQLAlchemy connection string used to connect to the '
+                    'slave database'),
+    cfg.IntOpt('idle_timeout',
+               default=3600,
+               deprecated_opts=[cfg.DeprecatedOpt('sql_idle_timeout',
+                                                  group='DEFAULT'),
+                                cfg.DeprecatedOpt('sql_idle_timeout',
+                                                  group='DATABASE')],
+               help='timeout before idle sql connections are reaped'),
+    cfg.IntOpt('min_pool_size',
+               default=1,
+               deprecated_opts=[cfg.DeprecatedOpt('sql_min_pool_size',
+                                                  group='DEFAULT'),
+                                cfg.DeprecatedOpt('sql_min_pool_size',
+                                                  group='DATABASE')],
+               help='Minimum number of SQL connections to keep open in a '
+                    'pool'),
+    cfg.IntOpt('max_pool_size',
+               default=None,
+               deprecated_opts=[cfg.DeprecatedOpt('sql_max_pool_size',
+                                                  group='DEFAULT'),
+                                cfg.DeprecatedOpt('sql_max_pool_size',
+                                                  group='DATABASE')],
+               help='Maximum number of SQL connections to keep open in a '
+                    'pool'),
+    cfg.IntOpt('max_retries',
+               default=10,
+               deprecated_opts=[cfg.DeprecatedOpt('sql_max_retries',
+                                                  group='DEFAULT'),
+                                cfg.DeprecatedOpt('sql_max_retries',
+                                                  group='DATABASE')],
+               help='maximum db connection retries during startup. '
+                    '(setting -1 implies an infinite retry count)'),
+    cfg.IntOpt('retry_interval',
+               default=10,
+               deprecated_opts=[cfg.DeprecatedOpt('sql_retry_interval',
+                                                  group='DEFAULT'),
+                                cfg.DeprecatedOpt('reconnect_interval',
+                                                  group='DATABASE')],
+               help='interval between retries of opening a sql connection'),
+    cfg.IntOpt('max_overflow',
+               default=None,
+               deprecated_opts=[cfg.DeprecatedOpt('sql_max_overflow',
+                                                  group='DEFAULT'),
+                                cfg.DeprecatedOpt('sqlalchemy_max_overflow',
+                                                  group='DATABASE')],
+               help='If set, use this value for max_overflow with sqlalchemy'),
+    cfg.IntOpt('connection_debug',
+               default=0,
+               deprecated_opts=[cfg.DeprecatedOpt('sql_connection_debug',
+                                                  group='DEFAULT')],
+               help='Verbosity of SQL debugging information. 0=None, '
+                    '100=Everything'),
+    cfg.BoolOpt('connection_trace',
+                default=False,
+                deprecated_opts=[cfg.DeprecatedOpt('sql_connection_trace',
+                                                   group='DEFAULT')],
+                help='Add python stack traces to SQL as comment strings'),
+    cfg.IntOpt('pool_timeout',
+               default=None,
+               deprecated_opts=[cfg.DeprecatedOpt('sqlalchemy_pool_timeout',
+                                                  group='DATABASE')],
+               help='If set, use this value for pool_timeout with sqlalchemy'),
+]
+
+CONF = cfg.CONF
+CONF.register_opts(sqlite_db_opts)
+CONF.register_opts(database_opts, 'database')
+
+LOG = logging.getLogger(__name__)
+
+_ENGINE = None
+_MAKER = None
+_SLAVE_ENGINE = None
+_SLAVE_MAKER = None
+
+
+def set_defaults(sql_connection, sqlite_db, max_pool_size=None,
+                 max_overflow=None, pool_timeout=None):
+    """Set defaults for configuration variables."""
+    cfg.set_defaults(database_opts,
+                     connection=sql_connection)
+    cfg.set_defaults(sqlite_db_opts,
+                     sqlite_db=sqlite_db)
+    # Update the QueuePool defaults
+    if max_pool_size is not None:
+        cfg.set_defaults(database_opts,
+                         max_pool_size=max_pool_size)
+    if max_overflow is not None:
+        cfg.set_defaults(database_opts,
+                         max_overflow=max_overflow)
+    if pool_timeout is not None:
+        cfg.set_defaults(database_opts,
+                         pool_timeout=pool_timeout)
+
+
+def cleanup():
+    global _ENGINE, _MAKER
+    global _SLAVE_ENGINE, _SLAVE_MAKER
+
+    if _MAKER:
+        _MAKER.close_all()
+        _MAKER = None
+    if _ENGINE:
+        _ENGINE.dispose()
+        _ENGINE = None
+    if _SLAVE_MAKER:
+        _SLAVE_MAKER.close_all()
+        _SLAVE_MAKER = None
+    if _SLAVE_ENGINE:
+        _SLAVE_ENGINE.dispose()
+        _SLAVE_ENGINE = None
+
+
+class SqliteForeignKeysListener(PoolListener):
+    """Ensures that the foreign key constraints are enforced in SQLite.
+
+    The foreign key constraints are disabled by default in SQLite,
+    so the foreign key constraints will be enabled here for every
+    database connection
+    """
+    def connect(self, dbapi_con, con_record):
+        dbapi_con.execute('pragma foreign_keys=ON')
+
+
+def get_session(autocommit=True, expire_on_commit=False,
+                sqlite_fk=False, slave_session=False):
+    """Return a SQLAlchemy session."""
+    global _MAKER
+    global _SLAVE_MAKER
+    maker = _MAKER
+
+    if slave_session:
+        maker = _SLAVE_MAKER
+
+    if maker is None:
+        engine = get_engine(sqlite_fk=sqlite_fk, slave_engine=slave_session)
+        maker = get_maker(engine, autocommit, expire_on_commit)
+
+    if slave_session:
+        _SLAVE_MAKER = maker
+    else:
+        _MAKER = maker
+
+    session = maker()
+    return session
+
+
+# note(boris-42): In current versions of DB backends unique constraint
+# violation messages follow the structure:
+#
+# sqlite:
+# 1 column - (IntegrityError) column c1 is not unique
+# N columns - (IntegrityError) column c1, c2, ..., N are not unique
+#
+# postgres:
+# 1 column - (IntegrityError) duplicate key value violates unique
+#               constraint "users_c1_key"
+# N columns - (IntegrityError) duplicate key value violates unique
+#               constraint "name_of_our_constraint"
+#
+# mysql:
+# 1 column - (IntegrityError) (1062, "Duplicate entry 'value_of_c1' for key
+#               'c1'")
+# N columns - (IntegrityError) (1062, "Duplicate entry 'values joined
+#               with -' for key 'name_of_our_constraint'")
+_DUP_KEY_RE_DB = {
+    "sqlite": re.compile(r"^.*columns?([^)]+)(is|are)\s+not\s+unique$"),
+    "postgresql": re.compile(r"^.*duplicate\s+key.*\"([^\"]+)\"\s*\n.*$"),
+    "mysql": re.compile(r"^.*\(1062,.*'([^\']+)'\"\)$")
+}
+
+
+def _raise_if_duplicate_entry_error(integrity_error, engine_name):
+    """Raise exception if two entries are duplicated.
+
+    In this function will be raised DBDuplicateEntry exception if integrity
+    error wrap unique constraint violation.
+    """
+
+    def get_columns_from_uniq_cons_or_name(columns):
+        # note(vsergeyev): UniqueConstraint name convention: "uniq_t0c10c2"
+        #                  where `t` it is table name and columns `c1`, `c2`
+        #                  are in UniqueConstraint.
+        uniqbase = "uniq_"
+        if not columns.startswith(uniqbase):
+            if engine_name == "postgresql":
+                return [columns[columns.index("_") + 1:columns.rindex("_")]]
+            return [columns]
+        return columns[len(uniqbase):].split("0")[1:]
+
+    if engine_name not in ["mysql", "sqlite", "postgresql"]:
+        return
+
+    # FIXME(johannes): The usage of the .message attribute has been
+    # deprecated since Python 2.6. However, the exceptions raised by
+    # SQLAlchemy can differ when using unicode() and accessing .message.
+    # An audit across all three supported engines will be necessary to
+    # ensure there are no regressions.
+    m = _DUP_KEY_RE_DB[engine_name].match(integrity_error.message)
+    if not m:
+        return
+    columns = m.group(1)
+
+    if engine_name == "sqlite":
+        columns = columns.strip().split(", ")
+    else:
+        columns = get_columns_from_uniq_cons_or_name(columns)
+    raise exception.DBDuplicateEntry(columns, integrity_error)
+
+
+# NOTE(comstud): In current versions of DB backends, Deadlock violation
+# messages follow the structure:
+#
+# mysql:
+# (OperationalError) (1213, 'Deadlock found when trying to get lock; try '
+#                     'restarting transaction') <query_str> <query_args>
+_DEADLOCK_RE_DB = {
+    "mysql": re.compile(r"^.*\(1213, 'Deadlock.*")
+}
+
+
+def _raise_if_deadlock_error(operational_error, engine_name):
+    """Raise exception on deadlock condition.
+
+    Raise DBDeadlock exception if OperationalError contains a Deadlock
+    condition.
+    """
+    re = _DEADLOCK_RE_DB.get(engine_name)
+    if re is None:
+        return
+    # FIXME(johannes): The usage of the .message attribute has been
+    # deprecated since Python 2.6. However, the exceptions raised by
+    # SQLAlchemy can differ when using unicode() and accessing .message.
+    # An audit across all three supported engines will be necessary to
+    # ensure there are no regressions.
+    m = re.match(operational_error.message)
+    if not m:
+        return
+    raise exception.DBDeadlock(operational_error)
+
+
+def _wrap_db_error(f):
+    @functools.wraps(f)
+    def _wrap(*args, **kwargs):
+        try:
+            return f(*args, **kwargs)
+        except UnicodeEncodeError:
+            raise exception.DBInvalidUnicodeParameter()
+        # note(boris-42): We should catch unique constraint violation and
+        # wrap it by our own DBDuplicateEntry exception. Unique constraint
+        # violation is wrapped by IntegrityError.
+        except sqla_exc.OperationalError as e:
+            _raise_if_deadlock_error(e, get_engine().name)
+            # NOTE(comstud): A lot of code is checking for OperationalError
+            # so let's not wrap it for now.
+            raise
+        except sqla_exc.IntegrityError as e:
+            # note(boris-42): SqlAlchemy doesn't unify errors from different
+            # DBs so we must do this. Also in some tables (for example
+            # instance_types) there are more than one unique constraint. This
+            # means we should get names of columns, which values violate
+            # unique constraint, from error message.
+            _raise_if_duplicate_entry_error(e, get_engine().name)
+            raise exception.DBError(e)
+        except Exception as e:
+            LOG.exception(_('DB exception wrapped.'))
+            raise exception.DBError(e)
+    return _wrap
+
+
+def get_engine(sqlite_fk=False, slave_engine=False):
+    """Return a SQLAlchemy engine."""
+    global _ENGINE
+    global _SLAVE_ENGINE
+    engine = _ENGINE
+    db_uri = CONF.database.connection
+
+    if slave_engine:
+        engine = _SLAVE_ENGINE
+        db_uri = CONF.database.slave_connection
+
+    if engine is None:
+        engine = create_engine(db_uri,
+                               sqlite_fk=sqlite_fk)
+    if slave_engine:
+        _SLAVE_ENGINE = engine
+    else:
+        _ENGINE = engine
+
+    return engine
+
+
+def _synchronous_switch_listener(dbapi_conn, connection_rec):
+    """Switch sqlite connections to non-synchronous mode."""
+    dbapi_conn.execute("PRAGMA synchronous = OFF")
+
+
+def _add_regexp_listener(dbapi_con, con_record):
+    """Add REGEXP function to sqlite connections."""
+
+    def regexp(expr, item):
+        reg = re.compile(expr)
+        return reg.search(six.text_type(item)) is not None
+    dbapi_con.create_function('regexp', 2, regexp)
+
+
+def _greenthread_yield(dbapi_con, con_record):
+    """Ensure other greenthreads get a chance to be executed.
+
+    Force a context switch. With common database backends (eg MySQLdb and
+    sqlite), there is no implicit yield caused by network I/O since they are
+    implemented by C libraries that eventlet cannot monkey patch.
+    """
+    greenthread.sleep(0)
+
+
+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 as ex:
+        if ex.args[0] in (2006, 2013, 2014, 2045, 2055):
+            LOG.warn(_('Got mysql server has gone away: %s'), ex)
+            raise sqla_exc.DisconnectionError("Database server went away")
+        else:
+            raise
+
+
+def _is_db_connection_error(args):
+    """Return True if error in connecting to db."""
+    # NOTE(adam_g): This is currently MySQL specific and needs to be extended
+    #               to support Postgres and others.
+    conn_err_codes = ('2002', '2003', '2006')
+    for err_code in conn_err_codes:
+        if args.find(err_code) != -1:
+            return True
+    return False
+
+
+def create_engine(sql_connection, sqlite_fk=False):
+    """Return a new SQLAlchemy engine."""
+    # NOTE(geekinutah): At this point we could be connecting to the normal
+    #                   db handle or the slave db handle. Things like
+    #                   _wrap_db_error aren't going to work well if their
+    #                   backends don't match. Let's check.
+    _assert_matching_drivers()
+    connection_dict = sqlalchemy.engine.url.make_url(sql_connection)
+
+    engine_args = {
+        "pool_recycle": CONF.database.idle_timeout,
+        "echo": False,
+        'convert_unicode': True,
+    }
+
+    # Map our SQL debug level to SQLAlchemy's options
+    if CONF.database.connection_debug >= 100:
+        engine_args['echo'] = 'debug'
+    elif CONF.database.connection_debug >= 50:
+        engine_args['echo'] = True
+
+    if "sqlite" in connection_dict.drivername:
+        if sqlite_fk:
+            engine_args["listeners"] = [SqliteForeignKeysListener()]
+        engine_args["poolclass"] = NullPool
+
+        if CONF.database.connection == "sqlite://":
+            engine_args["poolclass"] = StaticPool
+            engine_args["connect_args"] = {'check_same_thread': False}
+    else:
+        if CONF.database.max_pool_size is not None:
+            engine_args['pool_size'] = CONF.database.max_pool_size
+        if CONF.database.max_overflow is not None:
+            engine_args['max_overflow'] = CONF.database.max_overflow
+        if CONF.database.pool_timeout is not None:
+            engine_args['pool_timeout'] = CONF.database.pool_timeout
+
+    engine = sqlalchemy.create_engine(sql_connection, **engine_args)
+
+    sqlalchemy.event.listen(engine, 'checkin', _greenthread_yield)
+
+    if 'mysql' in connection_dict.drivername:
+        sqlalchemy.event.listen(engine, 'checkout', _ping_listener)
+    elif 'sqlite' in connection_dict.drivername:
+        if not CONF.sqlite_synchronous:
+            sqlalchemy.event.listen(engine, 'connect',
+                                    _synchronous_switch_listener)
+        sqlalchemy.event.listen(engine, 'connect', _add_regexp_listener)
+
+    if (CONF.database.connection_trace and
+            engine.dialect.dbapi.__name__ == 'MySQLdb'):
+        _patch_mysqldb_with_stacktrace_comments()
+
+    try:
+        engine.connect()
+    except sqla_exc.OperationalError as e:
+        if not _is_db_connection_error(e.args[0]):
+            raise
+
+        remaining = CONF.database.max_retries
+        if remaining == -1:
+            remaining = 'infinite'
+        while True:
+            msg = _('SQL connection failed. %s attempts left.')
+            LOG.warn(msg % remaining)
+            if remaining != 'infinite':
+                remaining -= 1
+            time.sleep(CONF.database.retry_interval)
+            try:
+                engine.connect()
+                break
+            except sqla_exc.OperationalError as e:
+                if (remaining != 'infinite' and remaining == 0) or \
+                        not _is_db_connection_error(e.args[0]):
+                    raise
+    return engine
+
+
+class Query(sqlalchemy.orm.query.Query):
+    """Subclass of sqlalchemy.query with soft_delete() method."""
+    def soft_delete(self, synchronize_session='evaluate'):
+        return self.update({'deleted': literal_column('id'),
+                            'updated_at': literal_column('updated_at'),
+                            'deleted_at': timeutils.utcnow()},
+                           synchronize_session=synchronize_session)
+
+
+class Session(sqlalchemy.orm.session.Session):
+    """Custom Session class to avoid SqlAlchemy Session monkey patching."""
+    @_wrap_db_error
+    def query(self, *args, **kwargs):
+        return super(Session, self).query(*args, **kwargs)
+
+    @_wrap_db_error
+    def flush(self, *args, **kwargs):
+        return super(Session, self).flush(*args, **kwargs)
+
+    @_wrap_db_error
+    def execute(self, *args, **kwargs):
+        return super(Session, self).execute(*args, **kwargs)
+
+
+def get_maker(engine, autocommit=True, expire_on_commit=False):
+    """Return a SQLAlchemy sessionmaker using the given engine."""
+    return sqlalchemy.orm.sessionmaker(bind=engine,
+                                       class_=Session,
+                                       autocommit=autocommit,
+                                       expire_on_commit=expire_on_commit,
+                                       query_cls=Query)
+
+
+def _patch_mysqldb_with_stacktrace_comments():
+    """Adds current stack trace as a comment in queries.
+
+    Patches MySQLdb.cursors.BaseCursor._do_query.
+    """
+    import MySQLdb.cursors
+    import traceback
+
+    old_mysql_do_query = MySQLdb.cursors.BaseCursor._do_query
+
+    def _do_query(self, q):
+        stack = ''
+        for file, line, method, function in traceback.extract_stack():
+            # exclude various common things from trace
+            if file.endswith('session.py') and method == '_do_query':
+                continue
+            if file.endswith('api.py') and method == 'wrapper':
+                continue
+            if file.endswith('utils.py') and method == '_inner':
+                continue
+            if file.endswith('exception.py') and method == '_wrap':
+                continue
+            # db/api is just a wrapper around db/sqlalchemy/api
+            if file.endswith('db/api.py'):
+                continue
+            # only trace inside rally
+            index = file.rfind('rally')
+            if index == -1:
+                continue
+            stack += "File:%s:%s Method:%s() Line:%s | " \
+                     % (file[index:], line, method, function)
+
+        # strip trailing " | " from stack
+        if stack:
+            stack = stack[:-3]
+            qq = "%s /* %s */" % (q, stack)
+        else:
+            qq = q
+        old_mysql_do_query(self, qq)
+
+    setattr(MySQLdb.cursors.BaseCursor, '_do_query', _do_query)
+
+
+def _assert_matching_drivers():
+    """Make sure slave handle and normal handle have the same driver."""
+    # NOTE(geekinutah): There's no use case for writing to one backend and
+    #                 reading from another. Who knows what the future holds?
+    if CONF.database.slave_connection == '':
+        return
+
+    normal = sqlalchemy.engine.url.make_url(CONF.database.connection)
+    slave = sqlalchemy.engine.url.make_url(CONF.database.slave_connection)
+    assert normal.drivername == slave.drivername

rally/openstack/common/db/sqlalchemy/test_migrations.py

@@ -0,0 +1,289 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2010-2011 OpenStack Foundation
+# Copyright 2012-2013 IBM Corp.
+# 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.
+
+
+import commands
+import ConfigParser
+import os
+import urlparse
+
+import sqlalchemy
+import sqlalchemy.exc
+
+from rally.openstack.common import lockutils
+from rally.openstack.common import log as logging
+from rally.openstack.common import test
+
+LOG = logging.getLogger(__name__)
+
+
+def _get_connect_string(backend, user, passwd, database):
+    """Get database connection
+
+    Try to get a connection with a very specific set of values, if we get
+    these then we'll run the tests, otherwise they are skipped
+    """
+    if backend == "postgres":
+        backend = "postgresql+psycopg2"
+    elif backend == "mysql":
+        backend = "mysql+mysqldb"
+    else:
+        raise Exception("Unrecognized backend: '%s'" % backend)
+
+    return ("%(backend)s://%(user)s:%(passwd)s@localhost/%(database)s"
+            % {'backend': backend, 'user': user, 'passwd': passwd,
+               'database': database})
+
+
+def _is_backend_avail(backend, user, passwd, database):
+    try:
+        connect_uri = _get_connect_string(backend, user, passwd, database)
+        engine = sqlalchemy.create_engine(connect_uri)
+        connection = engine.connect()
+    except Exception:
+        # intentionally catch all to handle exceptions even if we don't
+        # have any backend code loaded.
+        return False
+    else:
+        connection.close()
+        engine.dispose()
+        return True
+
+
+def _have_mysql(user, passwd, database):
+    present = os.environ.get('TEST_MYSQL_PRESENT')
+    if present is None:
+        return _is_backend_avail('mysql', user, passwd, database)
+    return present.lower() in ('', 'true')
+
+
+def _have_postgresql(user, passwd, database):
+    present = os.environ.get('TEST_POSTGRESQL_PRESENT')
+    if present is None:
+        return _is_backend_avail('postgres', user, passwd, database)
+    return present.lower() in ('', 'true')
+
+
+def get_db_connection_info(conn_pieces):
+    database = conn_pieces.path.strip('/')
+    loc_pieces = conn_pieces.netloc.split('@')
+    host = loc_pieces[1]
+
+    auth_pieces = loc_pieces[0].split(':')
+    user = auth_pieces[0]
+    password = ""
+    if len(auth_pieces) > 1:
+        password = auth_pieces[1].strip()
+
+    return (user, password, database, host)
+
+
+class BaseMigrationTestCase(test.BaseTestCase):
+    """Base class fort testing of migration utils."""
+
+    def __init__(self, *args, **kwargs):
+        super(BaseMigrationTestCase, self).__init__(*args, **kwargs)
+
+        self.DEFAULT_CONFIG_FILE = os.path.join(os.path.dirname(__file__),
+                                                'test_migrations.conf')
+        # Test machines can set the TEST_MIGRATIONS_CONF variable
+        # to override the location of the config file for migration testing
+        self.CONFIG_FILE_PATH = os.environ.get('TEST_MIGRATIONS_CONF',
+                                               self.DEFAULT_CONFIG_FILE)
+        self.test_databases = {}
+        self.migration_api = None
+
+    def setUp(self):
+        super(BaseMigrationTestCase, self).setUp()
+
+        # Load test databases from the config file. Only do this
+        # once. No need to re-run this on each test...
+        LOG.debug('config_path is %s' % self.CONFIG_FILE_PATH)
+        if os.path.exists(self.CONFIG_FILE_PATH):
+            cp = ConfigParser.RawConfigParser()
+            try:
+                cp.read(self.CONFIG_FILE_PATH)
+                defaults = cp.defaults()
+                for key, value in defaults.items():
+                    self.test_databases[key] = value
+            except ConfigParser.ParsingError as e:
+                self.fail("Failed to read test_migrations.conf config "
+                          "file. Got error: %s" % e)
+        else:
+            self.fail("Failed to find test_migrations.conf config "
+                      "file.")
+
+        self.engines = {}
+        for key, value in self.test_databases.items():
+            self.engines[key] = sqlalchemy.create_engine(value)
+
+        # We start each test case with a completely blank slate.
+        self._reset_databases()
+
+    def tearDown(self):
+        # We destroy the test data store between each test case,
+        # and recreate it, which ensures that we have no side-effects
+        # from the tests
+        self._reset_databases()
+        super(BaseMigrationTestCase, self).tearDown()
+
+    def execute_cmd(self, cmd=None):
+        status, output = commands.getstatusoutput(cmd)
+        LOG.debug(output)
+        self.assertEqual(0, status,
+                         "Failed to run: %s\n%s" % (cmd, output))
+
+    @lockutils.synchronized('pgadmin', 'tests-', external=True)
+    def _reset_pg(self, conn_pieces):
+        (user, password, database, host) = get_db_connection_info(conn_pieces)
+        os.environ['PGPASSWORD'] = password
+        os.environ['PGUSER'] = user
+        # note(boris-42): We must create and drop database, we can't
+        # drop database which we have connected to, so for such
+        # operations there is a special database template1.
+        sqlcmd = ("psql -w -U %(user)s -h %(host)s -c"
+                  " '%(sql)s' -d template1")
+
+        sql = ("drop database if exists %s;") % database
+        droptable = sqlcmd % {'user': user, 'host': host, 'sql': sql}
+        self.execute_cmd(droptable)
+
+        sql = ("create database %s;") % database
+        createtable = sqlcmd % {'user': user, 'host': host, 'sql': sql}
+        self.execute_cmd(createtable)
+
+        os.unsetenv('PGPASSWORD')
+        os.unsetenv('PGUSER')
+
+    def _reset_databases(self):
+        for key, engine in self.engines.items():
+            conn_string = self.test_databases[key]
+            conn_pieces = urlparse.urlparse(conn_string)
+            engine.dispose()
+            if conn_string.startswith('sqlite'):
+                # We can just delete the SQLite database, which is
+                # the easiest and cleanest solution
+                db_path = conn_pieces.path.strip('/')
+                if os.path.exists(db_path):
+                    os.unlink(db_path)
+                # No need to recreate the SQLite DB. SQLite will
+                # create it for us if it's not there...
+            elif conn_string.startswith('mysql'):
+                # We can execute the MySQL client to destroy and re-create
+                # the MYSQL database, which is easier and less error-prone
+                # than using SQLAlchemy to do this via MetaData...trust me.
+                (user, password, database, host) = \
+                    get_db_connection_info(conn_pieces)
+                sql = ("drop database if exists %(db)s; "
+                       "create database %(db)s;") % {'db': database}
+                cmd = ("mysql -u \"%(user)s\" -p\"%(password)s\" -h %(host)s "
+                       "-e \"%(sql)s\"") % {'user': user, 'password': password,
+                                            'host': host, 'sql': sql}
+                self.execute_cmd(cmd)
+            elif conn_string.startswith('postgresql'):
+                self._reset_pg(conn_pieces)
+
+
+class WalkVersionsMixin(object):
+    def _walk_versions(self, engine=None, snake_walk=False, downgrade=True):
+        # Determine latest version script from the repo, then
+        # upgrade from 1 through to the latest, with no data
+        # in the databases. This just checks that the schema itself
+        # upgrades successfully.
+
+        # Place the database under version control
+        self.migration_api.version_control(engine, self.REPOSITORY,
+                                           self.INIT_VERSION)
+        self.assertEqual(self.INIT_VERSION,
+                         self.migration_api.db_version(engine,
+                                                       self.REPOSITORY))
+
+        LOG.debug('latest version is %s' % self.REPOSITORY.latest)
+        versions = range(self.INIT_VERSION + 1, self.REPOSITORY.latest + 1)
+
+        for version in versions:
+            # upgrade -> downgrade -> upgrade
+            self._migrate_up(engine, version, with_data=True)
+            if snake_walk:
+                downgraded = self._migrate_down(
+                    engine, version - 1, with_data=True)
+                if downgraded:
+                    self._migrate_up(engine, version)
+
+        if downgrade:
+            # Now walk it back down to 0 from the latest, testing
+            # the downgrade paths.
+            for version in reversed(versions):
+                # downgrade -> upgrade -> downgrade
+                downgraded = self._migrate_down(engine, version - 1)
+
+                if snake_walk and downgraded:
+                    self._migrate_up(engine, version)
+                    self._migrate_down(engine, version - 1)
+
+    def _migrate_down(self, engine, version, with_data=False):
+        try:
+            self.migration_api.downgrade(engine, self.REPOSITORY, version)
+        except NotImplementedError:
+            # NOTE(sirp): some migrations, namely release-level
+            # migrations, don't support a downgrade.
+            return False
+
+        self.assertEqual(
+            version, self.migration_api.db_version(engine, self.REPOSITORY))
+
+        # NOTE(sirp): `version` is what we're downgrading to (i.e. the 'target'
+        # version). So if we have any downgrade checks, they need to be run for
+        # the previous (higher numbered) migration.
+        if with_data:
+            post_downgrade = getattr(
+                self, "_post_downgrade_%03d" % (version + 1), None)
+            if post_downgrade:
+                post_downgrade(engine)
+
+        return True
+
+    def _migrate_up(self, engine, version, with_data=False):
+        """migrate up to a new version of the db.
+
+        We allow for data insertion and post checks at every
+        migration version with special _pre_upgrade_### and
+        _check_### functions in the main test.
+        """
+        # NOTE(sdague): try block is here because it's impossible to debug
+        # where a failed data migration happens otherwise
+        try:
+            if with_data:
+                data = None
+                pre_upgrade = getattr(
+                    self, "_pre_upgrade_%03d" % version, None)
+                if pre_upgrade:
+                    data = pre_upgrade(engine)
+
+            self.migration_api.upgrade(engine, self.REPOSITORY, version)
+            self.assertEqual(version,
+                             self.migration_api.db_version(engine,
+                                                           self.REPOSITORY))
+            if with_data:
+                check = getattr(self, "_check_%03d" % version, None)
+                if check:
+                    check(engine, data)
+        except Exception:
+            LOG.error("Failed to migrate to version %s on engine %s" %
+                      (version, engine))
+            raise

rally/openstack/common/db/sqlalchemy/utils.py

@@ -0,0 +1,501 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2010 United States Government as represented by the
+# Administrator of the National Aeronautics and Space Administration.
+# Copyright 2010-2011 OpenStack Foundation.
+# Copyright 2012 Justin Santa Barbara
+# 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.
+
+import re
+
+from migrate.changeset import UniqueConstraint
+import sqlalchemy
+from sqlalchemy import Boolean
+from sqlalchemy import CheckConstraint
+from sqlalchemy import Column
+from sqlalchemy.engine import reflection
+from sqlalchemy.ext.compiler import compiles
+from sqlalchemy import func
+from sqlalchemy import Index
+from sqlalchemy import Integer
+from sqlalchemy import MetaData
+from sqlalchemy.sql.expression import literal_column
+from sqlalchemy.sql.expression import UpdateBase
+from sqlalchemy.sql import select
+from sqlalchemy import String
+from sqlalchemy import Table
+from sqlalchemy.types import NullType
+
+from rally.openstack.common.gettextutils import _  # noqa
+
+from rally.openstack.common import log as logging
+from rally.openstack.common import timeutils
+
+
+LOG = logging.getLogger(__name__)
+
+_DBURL_REGEX = re.compile(r"[^:]+://([^:]+):([^@]+)@.+")
+
+
+def sanitize_db_url(url):
+    match = _DBURL_REGEX.match(url)
+    if match:
+        return '%s****:****%s' % (url[:match.start(1)], url[match.end(2):])
+    return url
+
+
+class InvalidSortKey(Exception):
+    message = _("Sort key supplied was not valid.")
+
+
+# copy from glance/db/sqlalchemy/api.py
+def paginate_query(query, model, limit, sort_keys, marker=None,
+                   sort_dir=None, sort_dirs=None):
+    """Returns a query with sorting / pagination criteria added.
+
+    Pagination works by requiring a unique sort_key, specified by sort_keys.
+    (If sort_keys is not unique, then we risk looping through values.)
+    We use the last row in the previous page as the 'marker' for pagination.
+    So we must return values that follow the passed marker in the order.
+    With a single-valued sort_key, this would be easy: sort_key > X.
+    With a compound-values sort_key, (k1, k2, k3) we must do this to repeat
+    the lexicographical ordering:
+    (k1 > X1) or (k1 == X1 && k2 > X2) or (k1 == X1 && k2 == X2 && k3 > X3)
+
+    We also have to cope with different sort_directions.
+
+    Typically, the id of the last row is used as the client-facing pagination
+    marker, then the actual marker object must be fetched from the db and
+    passed in to us as marker.
+
+    :param query: the query object to which we should add paging/sorting
+    :param model: the ORM model class
+    :param limit: maximum number of items to return
+    :param sort_keys: array of attributes by which results should be sorted
+    :param marker: the last item of the previous page; we returns the next
+                    results after this value.
+    :param sort_dir: direction in which results should be sorted (asc, desc)
+    :param sort_dirs: per-column array of sort_dirs, corresponding to sort_keys
+
+    :rtype: sqlalchemy.orm.query.Query
+    :return: The query with sorting/pagination added.
+    """
+
+    if 'id' not in sort_keys:
+        # TODO(justinsb): If this ever gives a false-positive, check
+        # the actual primary key, rather than assuming its id
+        LOG.warn(_('Id not in sort_keys; is sort_keys unique?'))
+
+    assert(not (sort_dir and sort_dirs))
+
+    # Default the sort direction to ascending
+    if sort_dirs is None and sort_dir is None:
+        sort_dir = 'asc'
+
+    # Ensure a per-column sort direction
+    if sort_dirs is None:
+        sort_dirs = [sort_dir for _sort_key in sort_keys]
+
+    assert(len(sort_dirs) == len(sort_keys))
+
+    # Add sorting
+    for current_sort_key, current_sort_dir in zip(sort_keys, sort_dirs):
+        try:
+            sort_dir_func = {
+                'asc': sqlalchemy.asc,
+                'desc': sqlalchemy.desc,
+            }[current_sort_dir]
+        except KeyError:
+            raise ValueError(_("Unknown sort direction, "
+                               "must be 'desc' or 'asc'"))
+        try:
+            sort_key_attr = getattr(model, current_sort_key)
+        except AttributeError:
+            raise InvalidSortKey()
+        query = query.order_by(sort_dir_func(sort_key_attr))
+
+    # Add pagination
+    if marker is not None:
+        marker_values = []
+        for sort_key in sort_keys:
+            v = getattr(marker, sort_key)
+            marker_values.append(v)
+
+        # Build up an array of sort criteria as in the docstring
+        criteria_list = []
+        for i in range(0, len(sort_keys)):
+            crit_attrs = []
+            for j in range(0, i):
+                model_attr = getattr(model, sort_keys[j])
+                crit_attrs.append((model_attr == marker_values[j]))
+
+            model_attr = getattr(model, sort_keys[i])
+            if sort_dirs[i] == 'desc':
+                crit_attrs.append((model_attr < marker_values[i]))
+            else:
+                crit_attrs.append((model_attr > marker_values[i]))
+
+            criteria = sqlalchemy.sql.and_(*crit_attrs)
+            criteria_list.append(criteria)
+
+        f = sqlalchemy.sql.or_(*criteria_list)
+        query = query.filter(f)
+
+    if limit is not None:
+        query = query.limit(limit)
+
+    return query
+
+
+def get_table(engine, name):
+    """Returns an sqlalchemy table dynamically from db.
+
+    Needed because the models don't work for us in migrations
+    as models will be far out of sync with the current data.
+    """
+    metadata = MetaData()
+    metadata.bind = engine
+    return Table(name, metadata, autoload=True)
+
+
+class InsertFromSelect(UpdateBase):
+    """Form the base for `INSERT INTO table (SELECT ... )` statement."""
+    def __init__(self, table, select):
+        self.table = table
+        self.select = select
+
+
+@compiles(InsertFromSelect)
+def visit_insert_from_select(element, compiler, **kw):
+    """Form the `INSERT INTO table (SELECT ... )` statement."""
+    return "INSERT INTO %s %s" % (
+        compiler.process(element.table, asfrom=True),
+        compiler.process(element.select))
+
+
+class ColumnError(Exception):
+    """Error raised when no column or an invalid column is found."""
+
+
+def _get_not_supported_column(col_name_col_instance, column_name):
+    try:
+        column = col_name_col_instance[column_name]
+    except KeyError:
+        msg = _("Please specify column %s in col_name_col_instance "
+                "param. It is required because column has unsupported "
+                "type by sqlite).")
+        raise ColumnError(msg % column_name)
+
+    if not isinstance(column, Column):
+        msg = _("col_name_col_instance param has wrong type of "
+                "column instance for column %s It should be instance "
+                "of sqlalchemy.Column.")
+        raise ColumnError(msg % column_name)
+    return column
+
+
+def drop_unique_constraint(migrate_engine, table_name, uc_name, *columns,
+                           **col_name_col_instance):
+    """Drop unique constraint from table.
+
+    This method drops UC from table and works for mysql, postgresql and sqlite.
+    In mysql and postgresql we are able to use "alter table" construction.
+    Sqlalchemy doesn't support some sqlite column types and replaces their
+    type with NullType in metadata. We process these columns and replace
+    NullType with the correct column type.
+
+    :param migrate_engine: sqlalchemy engine
+    :param table_name:     name of table that contains uniq constraint.
+    :param uc_name:        name of uniq constraint that will be dropped.
+    :param columns:        columns that are in uniq constraint.
+    :param col_name_col_instance:   contains pair column_name=column_instance.
+                            column_instance is instance of Column. These params
+                            are required only for columns that have unsupported
+                            types by sqlite. For example BigInteger.
+    """
+
+    meta = MetaData()
+    meta.bind = migrate_engine
+    t = Table(table_name, meta, autoload=True)
+
+    if migrate_engine.name == "sqlite":
+        override_cols = [
+            _get_not_supported_column(col_name_col_instance, col.name)
+            for col in t.columns
+            if isinstance(col.type, NullType)
+        ]
+        for col in override_cols:
+            t.columns.replace(col)
+
+    uc = UniqueConstraint(*columns, table=t, name=uc_name)
+    uc.drop()
+
+
+def drop_old_duplicate_entries_from_table(migrate_engine, table_name,
+                                          use_soft_delete, *uc_column_names):
+    """Drop all old rows having the same values for columns in uc_columns.
+
+    This method drop (or mark ad `deleted` if use_soft_delete is True) old
+    duplicate rows form table with name `table_name`.
+
+    :param migrate_engine:  Sqlalchemy engine
+    :param table_name:      Table with duplicates
+    :param use_soft_delete: If True - values will be marked as `deleted`,
+                            if False - values will be removed from table
+    :param uc_column_names: Unique constraint columns
+    """
+    meta = MetaData()
+    meta.bind = migrate_engine
+
+    table = Table(table_name, meta, autoload=True)
+    columns_for_group_by = [table.c[name] for name in uc_column_names]
+
+    columns_for_select = [func.max(table.c.id)]
+    columns_for_select.extend(columns_for_group_by)
+
+    duplicated_rows_select = select(columns_for_select,
+                                    group_by=columns_for_group_by,
+                                    having=func.count(table.c.id) > 1)
+
+    for row in migrate_engine.execute(duplicated_rows_select):
+        # NOTE(boris-42): Do not remove row that has the biggest ID.
+        delete_condition = table.c.id != row[0]
+        is_none = None  # workaround for pyflakes
+        delete_condition &= table.c.deleted_at == is_none
+        for name in uc_column_names:
+            delete_condition &= table.c[name] == row[name]
+
+        rows_to_delete_select = select([table.c.id]).where(delete_condition)
+        for row in migrate_engine.execute(rows_to_delete_select).fetchall():
+            LOG.info(_("Deleting duplicated row with id: %(id)s from table: "
+                       "%(table)s") % dict(id=row[0], table=table_name))
+
+        if use_soft_delete:
+            delete_statement = table.update().\
+                where(delete_condition).\
+                values({
+                    'deleted': literal_column('id'),
+                    'updated_at': literal_column('updated_at'),
+                    'deleted_at': timeutils.utcnow()
+                })
+        else:
+            delete_statement = table.delete().where(delete_condition)
+        migrate_engine.execute(delete_statement)
+
+
+def _get_default_deleted_value(table):
+    if isinstance(table.c.id.type, Integer):
+        return 0
+    if isinstance(table.c.id.type, String):
+        return ""
+    raise ColumnError(_("Unsupported id columns type"))
+
+
+def _restore_indexes_on_deleted_columns(migrate_engine, table_name, indexes):
+    table = get_table(migrate_engine, table_name)
+
+    insp = reflection.Inspector.from_engine(migrate_engine)
+    real_indexes = insp.get_indexes(table_name)
+    existing_index_names = dict(
+        [(index['name'], index['column_names']) for index in real_indexes])
+
+    # NOTE(boris-42): Restore indexes on `deleted` column
+    for index in indexes:
+        if 'deleted' not in index['column_names']:
+            continue
+        name = index['name']
+        if name in existing_index_names:
+            column_names = [table.c[c] for c in existing_index_names[name]]
+            old_index = Index(name, *column_names, unique=index["unique"])
+            old_index.drop(migrate_engine)
+
+        column_names = [table.c[c] for c in index['column_names']]
+        new_index = Index(index["name"], *column_names, unique=index["unique"])
+        new_index.create(migrate_engine)
+
+
+def change_deleted_column_type_to_boolean(migrate_engine, table_name,
+                                          **col_name_col_instance):
+    if migrate_engine.name == "sqlite":
+        return _change_deleted_column_type_to_boolean_sqlite(
+            migrate_engine, table_name, **col_name_col_instance)
+    insp = reflection.Inspector.from_engine(migrate_engine)
+    indexes = insp.get_indexes(table_name)
+
+    table = get_table(migrate_engine, table_name)
+
+    old_deleted = Column('old_deleted', Boolean, default=False)
+    old_deleted.create(table, populate_default=False)
+
+    table.update().\
+        where(table.c.deleted == table.c.id).\
+        values(old_deleted=True).\
+        execute()
+
+    table.c.deleted.drop()
+    table.c.old_deleted.alter(name="deleted")
+
+    _restore_indexes_on_deleted_columns(migrate_engine, table_name, indexes)
+
+
+def _change_deleted_column_type_to_boolean_sqlite(migrate_engine, table_name,
+                                                  **col_name_col_instance):
+    insp = reflection.Inspector.from_engine(migrate_engine)
+    table = get_table(migrate_engine, table_name)
+
+    columns = []
+    for column in table.columns:
+        column_copy = None
+        if column.name != "deleted":
+            if isinstance(column.type, NullType):
+                column_copy = _get_not_supported_column(col_name_col_instance,
+                                                        column.name)
+            else:
+                column_copy = column.copy()
+        else:
+            column_copy = Column('deleted', Boolean, default=0)
+        columns.append(column_copy)
+
+    constraints = [constraint.copy() for constraint in table.constraints]
+
+    meta = table.metadata
+    new_table = Table(table_name + "__tmp__", meta,
+                      *(columns + constraints))
+    new_table.create()
+
+    indexes = []
+    for index in insp.get_indexes(table_name):
+        column_names = [new_table.c[c] for c in index['column_names']]
+        indexes.append(Index(index["name"], *column_names,
+                             unique=index["unique"]))
+
+    c_select = []
+    for c in table.c:
+        if c.name != "deleted":
+            c_select.append(c)
+        else:
+            c_select.append(table.c.deleted == table.c.id)
+
+    ins = InsertFromSelect(new_table, select(c_select))
+    migrate_engine.execute(ins)
+
+    table.drop()
+    [index.create(migrate_engine) for index in indexes]
+
+    new_table.rename(table_name)
+    new_table.update().\
+        where(new_table.c.deleted == new_table.c.id).\
+        values(deleted=True).\
+        execute()
+
+
+def change_deleted_column_type_to_id_type(migrate_engine, table_name,
+                                          **col_name_col_instance):
+    if migrate_engine.name == "sqlite":
+        return _change_deleted_column_type_to_id_type_sqlite(
+            migrate_engine, table_name, **col_name_col_instance)
+    insp = reflection.Inspector.from_engine(migrate_engine)
+    indexes = insp.get_indexes(table_name)
+
+    table = get_table(migrate_engine, table_name)
+
+    new_deleted = Column('new_deleted', table.c.id.type,
+                         default=_get_default_deleted_value(table))
+    new_deleted.create(table, populate_default=True)
+
+    deleted = True  # workaround for pyflakes
+    table.update().\
+        where(table.c.deleted == deleted).\
+        values(new_deleted=table.c.id).\
+        execute()
+    table.c.deleted.drop()
+    table.c.new_deleted.alter(name="deleted")
+
+    _restore_indexes_on_deleted_columns(migrate_engine, table_name, indexes)
+
+
+def _change_deleted_column_type_to_id_type_sqlite(migrate_engine, table_name,
+                                                  **col_name_col_instance):
+    # NOTE(boris-42): sqlaclhemy-migrate can't drop column with check
+    #                 constraints in sqlite DB and our `deleted` column has
+    #                 2 check constraints. So there is only one way to remove
+    #                 these constraints:
+    #                 1) Create new table with the same columns, constraints
+    #                 and indexes. (except deleted column).
+    #                 2) Copy all data from old to new table.
+    #                 3) Drop old table.
+    #                 4) Rename new table to old table name.
+    insp = reflection.Inspector.from_engine(migrate_engine)
+    meta = MetaData(bind=migrate_engine)
+    table = Table(table_name, meta, autoload=True)
+    default_deleted_value = _get_default_deleted_value(table)
+
+    columns = []
+    for column in table.columns:
+        column_copy = None
+        if column.name != "deleted":
+            if isinstance(column.type, NullType):
+                column_copy = _get_not_supported_column(col_name_col_instance,
+                                                        column.name)
+            else:
+                column_copy = column.copy()
+        else:
+            column_copy = Column('deleted', table.c.id.type,
+                                 default=default_deleted_value)
+        columns.append(column_copy)
+
+    def is_deleted_column_constraint(constraint):
+        # NOTE(boris-42): There is no other way to check is CheckConstraint
+        #                 associated with deleted column.
+        if not isinstance(constraint, CheckConstraint):
+            return False
+        sqltext = str(constraint.sqltext)
+        return (sqltext.endswith("deleted in (0, 1)") or
+                sqltext.endswith("deleted IN (:deleted_1, :deleted_2)"))
+
+    constraints = []
+    for constraint in table.constraints:
+        if not is_deleted_column_constraint(constraint):
+            constraints.append(constraint.copy())
+
+    new_table = Table(table_name + "__tmp__", meta,
+                      *(columns + constraints))
+    new_table.create()
+
+    indexes = []
+    for index in insp.get_indexes(table_name):
+        column_names = [new_table.c[c] for c in index['column_names']]
+        indexes.append(Index(index["name"], *column_names,
+                             unique=index["unique"]))
+
+    ins = InsertFromSelect(new_table, table.select())
+    migrate_engine.execute(ins)
+
+    table.drop()
+    [index.create(migrate_engine) for index in indexes]
+
+    new_table.rename(table_name)
+    deleted = True  # workaround for pyflakes
+    new_table.update().\
+        where(new_table.c.deleted == deleted).\
+        values(deleted=new_table.c.id).\
+        execute()
+
+    # NOTE(boris-42): Fix value of deleted column: False -> "" or 0.
+    deleted = False  # workaround for pyflakes
+    new_table.update().\
+        where(new_table.c.deleted == deleted).\
+        values(deleted=default_deleted_value).\
+        execute()

rally/openstack/common/excutils.py

@@ -0,0 +1,99 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2011 OpenStack Foundation.
+# Copyright 2012, Red Hat, Inc.
+#
+#    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.
+
+"""
+Exception related utilities.
+"""
+
+import logging
+import sys
+import time
+import traceback
+
+from rally.openstack.common.gettextutils import _  # noqa
+
+
+class save_and_reraise_exception(object):
+    """Save current exception, run some code and then re-raise.
+
+    In some cases the exception context can be cleared, resulting in None
+    being attempted to be re-raised after an exception handler is run. This
+    can happen when eventlet switches greenthreads or when running an
+    exception handler, code raises and catches an exception. In both
+    cases the exception context will be cleared.
+
+    To work around this, we save the exception state, run handler code, and
+    then re-raise the original exception. If another exception occurs, the
+    saved exception is logged and the new exception is re-raised.
+
+    In some cases the caller may not want to re-raise the exception, and
+    for those circumstances this context provides a reraise flag that
+    can be used to suppress the exception.  For example:
+
+    except Exception:
+        with save_and_reraise_exception() as ctxt:
+            decide_if_need_reraise()
+            if not should_be_reraised:
+                ctxt.reraise = False
+    """
+    def __init__(self):
+        self.reraise = True
+
+    def __enter__(self):
+        self.type_, self.value, self.tb, = sys.exc_info()
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        if exc_type is not None:
+            logging.error(_('Original exception being dropped: %s'),
+                          traceback.format_exception(self.type_,
+                                                     self.value,
+                                                     self.tb))
+            return False
+        if self.reraise:
+            raise self.type_, self.value, self.tb
+
+
+def forever_retry_uncaught_exceptions(infunc):
+    def inner_func(*args, **kwargs):
+        last_log_time = 0
+        last_exc_message = None
+        exc_count = 0
+        while True:
+            try:
+                return infunc(*args, **kwargs)
+            except Exception as exc:
+                this_exc_message = unicode(exc)
+                if this_exc_message == last_exc_message:
+                    exc_count += 1
+                else:
+                    exc_count = 1
+                # Do not log any more frequently than once a minute unless
+                # the exception message changes
+                cur_time = int(time.time())
+                if (cur_time - last_log_time > 60 or
+                        this_exc_message != last_exc_message):
+                    logging.exception(
+                        _('Unexpected exception occurred %d time(s)... '
+                          'retrying.') % exc_count)
+                    last_log_time = cur_time
+                    last_exc_message = this_exc_message
+                    exc_count = 0
+                # This should be a very rare event. In case it isn't, do
+                # a sleep.
+                time.sleep(1)
+    return inner_func

rally/openstack/common/fileutils.py

@@ -0,0 +1,110 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2011 OpenStack Foundation.
+# 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.
+
+
+import contextlib
+import errno
+import os
+
+from rally.openstack.common import excutils
+from rally.openstack.common.gettextutils import _  # noqa
+from rally.openstack.common import log as logging
+
+LOG = logging.getLogger(__name__)
+
+_FILE_CACHE = {}
+
+
+def ensure_tree(path):
+    """Create a directory (and any ancestor directories required)
+
+    :param path: Directory to create
+    """
+    try:
+        os.makedirs(path)
+    except OSError as exc:
+        if exc.errno == errno.EEXIST:
+            if not os.path.isdir(path):
+                raise
+        else:
+            raise
+
+
+def read_cached_file(filename, force_reload=False):
+    """Read from a file if it has been modified.
+
+    :param force_reload: Whether to reload the file.
+    :returns: A tuple with a boolean specifying if the data is fresh
+              or not.
+    """
+    global _FILE_CACHE
+
+    if force_reload and filename in _FILE_CACHE:
+        del _FILE_CACHE[filename]
+
+    reloaded = False
+    mtime = os.path.getmtime(filename)
+    cache_info = _FILE_CACHE.setdefault(filename, {})
+
+    if not cache_info or mtime > cache_info.get('mtime', 0):
+        LOG.debug(_("Reloading cached file %s") % filename)
+        with open(filename) as fap:
+            cache_info['data'] = fap.read()
+        cache_info['mtime'] = mtime
+        reloaded = True
+    return (reloaded, cache_info['data'])
+
+
+def delete_if_exists(path):
+    """Delete a file, but ignore file not found error.
+
+    :param path: File to delete
+    """
+
+    try:
+        os.unlink(path)
+    except OSError as e:
+        if e.errno == errno.ENOENT:
+            return
+        else:
+            raise
+
+
+@contextlib.contextmanager
+def remove_path_on_error(path):
+    """Protect code that wants to operate on PATH atomically.
+    Any exception will cause PATH to be removed.
+
+    :param path: File to work with
+    """
+    try:
+        yield
+    except Exception:
+        with excutils.save_and_reraise_exception():
+            delete_if_exists(path)
+
+
+def file_open(*args, **kwargs):
+    """Open file
+
+    see built-in file() documentation for more details
+
+    Note: The reason this is kept in a separate module is to easily
+    be able to provide a stub module that doesn't alter system
+    state at all (for unit tests)
+    """
+    return file(*args, **kwargs)

rally/openstack/common/lockutils.py

@@ -0,0 +1,276 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2011 OpenStack Foundation.
+# 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.
+
+
+import contextlib
+import errno
+import functools
+import os
+import time
+import weakref
+
+from eventlet import semaphore
+from oslo.config import cfg
+
+from rally.openstack.common import fileutils
+from rally.openstack.common.gettextutils import _  # noqa
+from rally.openstack.common import local
+from rally.openstack.common import log as logging
+
+
+LOG = logging.getLogger(__name__)
+
+
+util_opts = [
+    cfg.BoolOpt('disable_process_locking', default=False,
+                help='Whether to disable inter-process locks'),
+    cfg.StrOpt('lock_path',
+               help=('Directory to use for lock files.'))
+]
+
+
+CONF = cfg.CONF
+CONF.register_opts(util_opts)
+
+
+def set_defaults(lock_path):
+    cfg.set_defaults(util_opts, lock_path=lock_path)
+
+
+class _InterProcessLock(object):
+    """Lock implementation which allows multiple locks, working around
+    issues like bugs.debian.org/cgi-bin/bugreport.cgi?bug=632857 and does
+    not require any cleanup. Since the lock is always held on a file
+    descriptor rather than outside of the process, the lock gets dropped
+    automatically if the process crashes, even if __exit__ is not executed.
+
+    There are no guarantees regarding usage by multiple green threads in a
+    single process here. This lock works only between processes. Exclusive
+    access between local threads should be achieved using the semaphores
+    in the @synchronized decorator.
+
+    Note these locks are released when the descriptor is closed, so it's not
+    safe to close the file descriptor while another green thread holds the
+    lock. Just opening and closing the lock file can break synchronisation,
+    so lock files must be accessed only using this abstraction.
+    """
+
+    def __init__(self, name):
+        self.lockfile = None
+        self.fname = name
+
+    def __enter__(self):
+        self.lockfile = open(self.fname, 'w')
+
+        while True:
+            try:
+                # Using non-blocking locks since green threads are not
+                # patched to deal with blocking locking calls.
+                # Also upon reading the MSDN docs for locking(), it seems
+                # to have a laughable 10 attempts "blocking" mechanism.
+                self.trylock()
+                return self
+            except IOError as e:
+                if e.errno in (errno.EACCES, errno.EAGAIN):
+                    # external locks synchronise things like iptables
+                    # updates - give it some time to prevent busy spinning
+                    time.sleep(0.01)
+                else:
+                    raise
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        try:
+            self.unlock()
+            self.lockfile.close()
+        except IOError:
+            LOG.exception(_("Could not release the acquired lock `%s`"),
+                          self.fname)
+
+    def trylock(self):
+        raise NotImplementedError()
+
+    def unlock(self):
+        raise NotImplementedError()
+
+
+class _WindowsLock(_InterProcessLock):
+    def trylock(self):
+        msvcrt.locking(self.lockfile.fileno(), msvcrt.LK_NBLCK, 1)
+
+    def unlock(self):
+        msvcrt.locking(self.lockfile.fileno(), msvcrt.LK_UNLCK, 1)
+
+
+class _PosixLock(_InterProcessLock):
+    def trylock(self):
+        fcntl.lockf(self.lockfile, fcntl.LOCK_EX | fcntl.LOCK_NB)
+
+    def unlock(self):
+        fcntl.lockf(self.lockfile, fcntl.LOCK_UN)
+
+
+if os.name == 'nt':
+    import msvcrt
+    InterProcessLock = _WindowsLock
+else:
+    import fcntl
+    InterProcessLock = _PosixLock
+
+_semaphores = weakref.WeakValueDictionary()
+
+
+@contextlib.contextmanager
+def lock(name, lock_file_prefix=None, external=False, lock_path=None):
+    """Context based lock
+
+    This function yields a `semaphore.Semaphore` instance unless external is
+    True, in which case, it'll yield an InterProcessLock instance.
+
+    :param lock_file_prefix: The lock_file_prefix argument is used to provide
+    lock files on disk with a meaningful prefix.
+
+    :param external: The external keyword argument denotes whether this lock
+    should work across multiple processes. This means that if two different
+    workers both run a a method decorated with @synchronized('mylock',
+    external=True), only one of them will execute at a time.
+
+    :param lock_path: The lock_path keyword argument is used to specify a
+    special location for external lock files to live. If nothing is set, then
+    CONF.lock_path is used as a default.
+    """
+    # NOTE(soren): If we ever go natively threaded, this will be racy.
+    #              See http://stackoverflow.com/questions/5390569/dyn
+    #              amically-allocating-and-destroying-mutexes
+    sem = _semaphores.get(name, semaphore.Semaphore())
+    if name not in _semaphores:
+        # this check is not racy - we're already holding ref locally
+        # so GC won't remove the item and there was no IO switch
+        # (only valid in greenthreads)
+        _semaphores[name] = sem
+
+    with sem:
+        LOG.debug(_('Got semaphore "%(lock)s"'), {'lock': name})
+
+        # NOTE(mikal): I know this looks odd
+        if not hasattr(local.strong_store, 'locks_held'):
+            local.strong_store.locks_held = []
+        local.strong_store.locks_held.append(name)
+
+        try:
+            if external and not CONF.disable_process_locking:
+                LOG.debug(_('Attempting to grab file lock "%(lock)s"'),
+                          {'lock': name})
+
+                # We need a copy of lock_path because it is non-local
+                local_lock_path = lock_path or CONF.lock_path
+                if not local_lock_path:
+                    raise cfg.RequiredOptError('lock_path')
+
+                if not os.path.exists(local_lock_path):
+                    fileutils.ensure_tree(local_lock_path)
+                    LOG.info(_('Created lock path: %s'), local_lock_path)
+
+                def add_prefix(name, prefix):
+                    if not prefix:
+                        return name
+                    sep = '' if prefix.endswith('-') else '-'
+                    return '%s%s%s' % (prefix, sep, name)
+
+                # NOTE(mikal): the lock name cannot contain directory
+                # separators
+                lock_file_name = add_prefix(name.replace(os.sep, '_'),
+                                            lock_file_prefix)
+
+                lock_file_path = os.path.join(local_lock_path, lock_file_name)
+
+                try:
+                    lock = InterProcessLock(lock_file_path)
+                    with lock as lock:
+                        LOG.debug(_('Got file lock "%(lock)s" at %(path)s'),
+                                  {'lock': name, 'path': lock_file_path})
+                        yield lock
+                finally:
+                    LOG.debug(_('Released file lock "%(lock)s" at %(path)s'),
+                              {'lock': name, 'path': lock_file_path})
+            else:
+                yield sem
+
+        finally:
+            local.strong_store.locks_held.remove(name)
+
+
+def synchronized(name, lock_file_prefix=None, external=False, lock_path=None):
+    """Synchronization decorator.
+
+    Decorating a method like so::
+
+        @synchronized('mylock')
+        def foo(self, *args):
+           ...
+
+    ensures that only one thread will execute the foo method at a time.
+
+    Different methods can share the same lock::
+
+        @synchronized('mylock')
+        def foo(self, *args):
+           ...
+
+        @synchronized('mylock')
+        def bar(self, *args):
+           ...
+
+    This way only one of either foo or bar can be executing at a time.
+    """
+
+    def wrap(f):
+        @functools.wraps(f)
+        def inner(*args, **kwargs):
+            with lock(name, lock_file_prefix, external, lock_path):
+                LOG.debug(_('Got semaphore / lock "%(function)s"'),
+                          {'function': f.__name__})
+                return f(*args, **kwargs)
+
+            LOG.debug(_('Semaphore / lock released "%(function)s"'),
+                      {'function': f.__name__})
+        return inner
+    return wrap
+
+
+def synchronized_with_prefix(lock_file_prefix):
+    """Partial object generator for the synchronization decorator.
+
+    Redefine @synchronized in each project like so::
+
+        (in nova/utils.py)
+        from nova.openstack.common import lockutils
+
+        synchronized = lockutils.synchronized_with_prefix('nova-')
+
+
+        (in nova/foo.py)
+        from nova import utils
+
+        @utils.synchronized('mylock')
+        def bar(self, *args):
+           ...
+
+    The lock_file_prefix argument is used to provide lock files on disk with a
+    meaningful prefix.
+    """
+
+    return functools.partial(synchronized, lock_file_prefix=lock_file_prefix)