Added alembic support for database migrations

Change-Id: If5923734315efcecc64127edb4abd3d6005c30ed

cloudkitty/common/db/alembic/alembic.ini

@@ -0,0 +1,59 @@
+# A generic, single database configuration.
+
+[alembic]
+# path to migration scripts
+script_location = alembic
+
+# template used to generate migration files
+# file_template = %%(rev)s_%%(slug)s
+
+# max length of characters to apply to the
+# "slug" field
+#truncate_slug_length = 40
+
+# set to 'true' to run the environment during
+# the 'revision' command, regardless of autogenerate
+# revision_environment = false
+
+# set to 'true' to allow .pyc and .pyo files without
+# a source .py file to be detected as revisions in the
+# versions/ directory
+# sourceless = false
+
+# sqlalchemy.url = driver://user:pass@localhost/dbname
+
+
+# Logging configuration
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S

cloudkitty/common/db/alembic/env.py

@@ -0,0 +1,43 @@
+# -*- coding: utf-8 -*-
+# Copyright 2014 Objectif Libre
+#
+#    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.
+#
+# @author: Stéphane Albert
+#
+from logging import config as log_config
+
+from alembic import context
+
+from cloudkitty import db
+
+config = context.config
+log_config.fileConfig(config.config_file_name)
+
+
+def run_migrations_online(target_metadata, version_table):
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    :param target_metadata: Model's metadata used for autogenerate support.
+    :param version_table: Override the default version table for alembic.
+    """
+    engine = db.get_engine()
+    with engine.connect() as connection:
+        context.configure(connection=connection,
+                          target_metadata=target_metadata,
+                          version_table=version_table)
+        with context.begin_transaction():
+            context.run_migrations()

cloudkitty/common/db/alembic/migration.py

@@ -0,0 +1,70 @@
+# -*- coding: utf-8 -*-
+# Copyright 2014 Objectif Libre
+#
+#    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.
+#
+# @author: Stéphane Albert
+#
+import os
+
+import alembic
+from alembic import config as alembic_config
+
+ALEMBIC_INI_PATH = os.path.join(os.path.dirname(__file__), 'alembic.ini')
+
+
+def load_alembic_config(repo_path, ini_path=ALEMBIC_INI_PATH):
+    if not os.path.exists(repo_path):
+        raise Exception('Repo path (%s) not found.' % repo_path)
+    if not os.path.exists(ini_path):
+        raise Exception('Ini path (%s) not found.' % ini_path)
+    config = alembic_config.Config(ini_path)
+    config.set_main_option('script_location', repo_path)
+    return config
+
+
+def upgrade(config, version):
+    return alembic.command.upgrade(config, version or 'head')
+
+
+def downgrade(config, version):
+    if isinstance(version, int) or version is None or version.isdigit():
+        version = 'base'
+    return alembic.command.downgrade(config, version)
+
+
+def version(config):
+    return alembic.command.current(config)
+
+
+def revision(config, message='', autogenerate=False):
+    """Creates template for migration.
+
+    :param message: Text that will be used for migration title
+    :type message: string
+    :param autogenerate: If True - generates diff based on current database
+                            state
+    :type autogenerate: bool
+    """
+    return alembic.command.revision(config, message=message,
+                                    autogenerate=autogenerate)
+
+
+def stamp(config, revision):
+    """Stamps database with provided revision.
+
+    :param revision: Should match one from repository or head - to stamp
+                        database with most recent revision
+    :type revision: string
+    """
+    return alembic.command.stamp(config, revision=revision)