Add tag table in db and migration file

Add a new table named 'server_tags' in mogan database. and
provide a migration script to upgrade the old datbase.

Change-Id: I509d4db82d2aaa4c75ba93812ff0055eb3bd56f7
Implements: blueprint server-tags-support

mogan/db/sqlalchemy/alembic/versions/cf73c09d3ff2_add_server_tags.py

@@ -0,0 +1,43 @@
+#
+#    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.
+
+"""add server tags
+
+Revision ID: cf73c09d3ff2
+Revises: 0de89f877016
+Create Date: 2017-09-21 04:11:09.636891
+
+"""
+
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers, used by Alembic.
+revision = 'cf73c09d3ff2'
+down_revision = '91941bf1ebc9'
+
+
+def upgrade():
+    op.create_table(
+        'server_tags',
+        sa.Column('created_at', sa.DateTime(), nullable=True),
+        sa.Column('updated_at', sa.DateTime(), nullable=True),
+        sa.Column('server_id', sa.Integer(), nullable=False),
+        sa.Column('tag', sa.String(length=255), nullable=False),
+        sa.PrimaryKeyConstraint('server_id', 'tag'),
+        sa.ForeignKeyConstraint(['server_id'],
+                                ['servers.id']),
+        sa.Index('server_tags_tag_idx', 'tag'),
+        mysql_ENGINE='InnoDB',
+        mysql_DEFAULT_CHARSET='UTF8'
+    )

mogan/db/sqlalchemy/models.py

@@ -373,3 +373,15 @@ class ServerGroup(Base):
     @property
     def members(self):
         return [m.server_uuid for m in self._members]
+
+
+class ServerTag(Base):
+    """Represents a tag of a bare metal server."""
+
+    __tablename__ = 'server_tags'
+    __table_args__ = (
+        Index('server_tags_tag_idx', 'tag'),
+        table_args())
+    server_id = Column(Integer, ForeignKey('servers.id'),
+                       primary_key=True, nullable=False)
+    tag = Column(String(255), primary_key=True, nullable=False)

mogan/tests/unit/db/sqlalchemy/test_migrations.py

@@ -245,6 +245,21 @@ class MigrationCheckersMixin(object):
         self.assertIsInstance(nodes.c.resource_name.type,
                               sqlalchemy.types.String)
 
+    def _check_cf73c09d3ff2(self, engine, data):
+        server_tags = db_utils.get_table(engine, 'server_tags')
+        col_names = [column.name for column in server_tags.c]
+        self.assertIn('tag', col_names)
+        self.assertIsInstance(server_tags.c.tag.type,
+                              sqlalchemy.types.String)
+        servers = db_utils.get_table(engine, 'servers')
+        data = {'id': '123', 'name': 'server1'}
+        servers.insert().execute(data)
+        data = {'server_id': '123', 'tag': 'tag1'}
+        server_tags.insert().execute(data)
+        tag = server_tags.select(server_tags.c.server_id == '123').execute().\
+            first()
+        self.assertEqual('tag1', tag['tag'])
+
     def test_upgrade_and_version(self):
         with patch_with_engine(self.engine):
             self.migration_api.upgrade('head')