Enable migration autogenerate

These changes allow a developer to generate migrations using the
autogenerate function without the need to pass in a config file that
includes sql connection information.

Change-Id: I6b3942f7747e8f73e52925c24340e20daeb78911

CONTRIBUTING.rst

@@ -239,16 +239,15 @@ Writing a Plugin
 .. _ironic_inspector.plugins.base: https://github.com/openstack/ironic-inspector/blob/master/ironic_inspector/plugins/base.py
 .. _Introspection Rules: https://github.com/openstack/ironic-inspector#introspection-rules
 
-Adding migrations to the database
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Making changes to the database
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-In order to make any changes to the database, you must add a new migration.
-This can be done using alembic::
+In order to make a change to the ironic-inspector database you must update the
+database models found in ironic_inspector.db_ and then create a migration to
+reflect that change.
 
-    alembic --config ironic_inspector/alembic.ini revision -m "A short description"
-
-This will generate an empty migration file, with the correct revision
-information already included. In this file there are two functions:
+There are two ways to create a migration which are described below, both of
+these generate a new migration file. In this file there are two functions:
 
 * upgrade - The upgrade function is run when
     ``ironic-inspector-dbsync upgrade`` is run, and should be populated with
@@ -262,4 +261,31 @@ information already included. In this file there are two functions:
 For further information on creating a migration, refer to
 `Create a Migration Script`_ from the alembic documentation.
 
+Autogenerate
+------------
+
+This is the simplest way to create a migration. Alembic will compare the models
+to an up to date database, and then attempt to write a migration based on the
+differences. This should generate correct migrations in most cases however
+there are some cases when it can not detect some changes and may require
+manual modification, see `What does Autogenerate Detect (and what does it not
+detect?)`_ from the alembic documentation.
+
+::
+
+    ironic-inspector-dbsync upgrade
+    ironic-inspector-dbsync revision -m "A short description" --autogenerate
+
+Manual
+------
+
+This will generate an empty migration file, with the correct revision
+information already included. However upgrade and downgrade are left empty and
+must be manually populated in order to perform the correct actions on the
+database::
+
+    ironic-inspector-dbsync revision -m "A short description"
+
 .. _Create a Migration Script: https://alembic.readthedocs.org/en/latest/tutorial.html#create-a-migration-script
+.. _ironic_inspector.db: https://github.com/openstack/ironic-inspector/blob/master/ironic_inspector/db.py
+.. _What does Autogenerate Detect (and what does it not detect?): http://alembic.readthedocs.org/en/latest/autogenerate.html#what-does-autogenerate-detect-and-what-does-it-not-detect

ironic_inspector/db.py

@@ -27,6 +27,8 @@ from sqlalchemy import (Boolean, Column, DateTime, Float, ForeignKey, Integer,
 from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy import orm
 
+from ironic_inspector import conf  # noqa
+
 
 class ModelBase(models.ModelBase):
     __table_args__ = {'mysql_engine': "InnoDB",
@@ -35,9 +37,16 @@ class ModelBase(models.ModelBase):
 
 Base = declarative_base(cls=ModelBase)
 CONF = cfg.CONF
-
+_DEFAULT_SQL_CONNECTION = 'sqlite:///ironic_inspector.sqlite'
 _FACADE = None
 
+db_opts.set_defaults(cfg.CONF, _DEFAULT_SQL_CONNECTION,
+                     'ironic_inspector.sqlite')
+if CONF.discoverd.database:
+    db_opts.set_defaults(CONF,
+                         connection='sqlite:///%s' %
+                         str(CONF.discoverd.database).strip())
+
 
 class Node(Base):
     __tablename__ = 'nodes'
@@ -110,20 +119,16 @@ class RuleAction(Base):
 
 def init():
     """Initialize the database."""
-    if CONF.discoverd.database:
-        db_opts.set_defaults(CONF,
-                             connection='sqlite:///%s' %
-                             str(CONF.discoverd.database).strip())
     return get_session()
 
 
 def get_session(**kwargs):
-    facade = _create_facade_lazily()
+    facade = create_facade_lazily()
     return facade.get_session(**kwargs)
 
 
 def get_engine():
-    facade = _create_facade_lazily()
+    facade = create_facade_lazily()
     return facade.get_engine()
 
 
@@ -138,7 +143,7 @@ def model_query(model, *args, **kwargs):
     return query
 
 
-def _create_facade_lazily():
+def create_facade_lazily():
     global _FACADE
     if _FACADE is None:
         _FACADE = db_session.EngineFacade.from_config(cfg.CONF)

ironic_inspector/dbsync.py

@@ -22,13 +22,11 @@ from alembic import config as alembic_config
 from alembic import util as alembic_util
 
 from oslo_config import cfg
-from oslo_db import options as db_opts
 from oslo_log import log
 
 from ironic_inspector import conf  # noqa
 
 CONF = cfg.CONF
-db_opts.set_defaults(CONF)
 
 
 def add_alembic_command(subparsers, name):
@@ -53,6 +51,7 @@ def add_command_parsers(subparsers):
     parser = add_alembic_command(subparsers, 'revision')
     parser.set_defaults(func=do_revision)
     parser.add_argument('-m', '--message')
+    parser.add_argument('--autogenerate', action='store_true')
 
 
 command_opt = cfg.SubCommandOpt('command',
@@ -64,7 +63,8 @@ CONF.register_cli_opt(command_opt)
 
 
 def do_revision(config, cmd, *args, **kwargs):
-    do_alembic_command(config, cmd, message=CONF.command.message)
+    do_alembic_command(config, cmd, message=CONF.command.message,
+                       autogenerate=CONF.command.autogenerate)
 
 
 def with_revision(config, cmd, *args, **kwargs):

ironic_inspector/migrations/env.py

@@ -14,7 +14,8 @@
 
 from alembic import context
 from logging.config import fileConfig
-from sqlalchemy import create_engine
+
+from ironic_inspector import db
 
 # this is the Alembic Config object, which provides
 # access to the values within the .ini file in use.
@@ -29,7 +30,6 @@ fileConfig(config.config_file_name)
 # for 'autogenerate' support
 # from myapp import mymodel
 # target_metadata = mymodel.Base.metadata
-from ironic_inspector import db
 target_metadata = db.Base.metadata
 
 # other values from the config, defined by the needs of env.py,
@@ -65,8 +65,7 @@ def run_migrations_online():
     and associate a connection with the context.
 
     """
-    connectable = create_engine(ironic_inspector_config.database.connection)
-
+    connectable = db.create_facade_lazily().get_engine()
     with connectable.connect() as connection:
         context.configure(
             connection=connection,

ironic_inspector/test/base.py

@@ -15,7 +15,6 @@ import unittest
 
 import mock
 from oslo_config import cfg
-from oslo_db import options as db_opts
 from oslo_log import log
 
 from ironic_inspector.common import i18n
@@ -35,7 +34,7 @@ def init_test_conf():
         # Unit tests
     except Exception:
         CONF.reset()
-    for group in ('firewall', 'processing', 'ironic'):
+    for group in ('firewall', 'processing', 'ironic', 'discoverd'):
         CONF.register_group(cfg.OptGroup(group))
     try:
         # Functional tests
@@ -43,13 +42,9 @@ def init_test_conf():
     except Exception:
         # Unit tests
         pass
-    db_opts.set_defaults(CONF)
+    CONF.set_default('connection', "sqlite:///", group='database')
     CONF.set_default('slave_connection', False, group='database')
     CONF.set_default('max_retries', 10, group='database')
-    if not CONF.database.connection:
-        # Might be set in functional tests
-        db_opts.set_defaults(CONF,
-                             connection='sqlite:///')
 
 
 class BaseTest(unittest.TestCase):