Move sqlalchemy migration from Nova

Added functions for work with migration scripts to
openstack/common/db/sqlalchemy/migration.py file. This code can be used
in Nova, Cinder, Glance, etc. Added new DbMigrationError exception to
openstack/common/db/exception.py file.
Tests added.

blueprint test-migrations

Change-Id: Ia63f7fb89b0a6baacf3fd424c0db09c74680af4a

2 files changed, 125 insertions, 0 deletions

diff --git a/openstack/common/db/exception.py b/openstack/common/db/exception.py
index 69905da..3627de2 100644
--- a/openstack/common/db/exception.py
+++ b/openstack/common/db/exception.py
@@ -43,3 +43,9 @@ class DBDeadlock(DBError):
 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))
diff --git a/openstack/common/db/sqlalchemy/migration.py b/openstack/common/db/sqlalchemy/migration.py
index e643d8e..4154359 100644
--- a/openstack/common/db/sqlalchemy/migration.py
+++ b/openstack/common/db/sqlalchemy/migration.py
@@ -38,12 +38,53 @@
 # 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 openstack.common.db import exception
+from openstack.common.db.sqlalchemy import session as db_session
+from 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
@@ -157,3 +198,81 @@ def patch_migrate():
         _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