sahara-api should not create DB from metadata

[Dmitry Mescheryakov]

Right now we create DB tables on sahara-api start:
https://github.com/openstack/sahara/blob/master/sahara/cli/sahara_api.py#L61

We do this by creating tables from metadata. That is not right because we support alembic migrations. With alembic tables could be created with:
sahara-db-manage upgrade head

Comparing these two ways the second one is superior. Creating tables from metadata works _only_ by creating new tables from scratch. Alembic supports not just DB creation, but migrations as well out of the box. I.e. when a new Sahara project releases, user will just run the same 'sahara-db-manage upgrade head', and his DB will be migrated to a new version preserving all the data.

There is no sense in keeping tables creation from metadata, since alembic already does that. But also we should not run alembic migrations automatically on start. Managing DB is a serious task and should be performed by person, and not implicitly by server itself. For instance, a person might decide to take a backup before proceeding with upgrade.

[Sergey Lukjanov (slukjanov)]

So, some additional notes:

* it'll remove implicit db management;
* it was already approved https://review.openstack.org/#/c/68631/2/savanna/main.py but it's missing one more place where db auto-created, so, it means that overall approach was applied and approved months ago, but it's a bug in this approach.

[Matthew Farrellee (mattf)]

please justify the urgency for making this change so close to the release date.

for instance, what happens if we do not get this into icehouse?

[Dmitry Mescheryakov (dmitrymex)]

For the record, we discussed that in the chat. The main driver in fixing this right now is that if a user create database from metadata, he will not be able to migrate from Icehouse to Juno. Only databases created by alembic could be migrated to the later version.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/82750
Committed: https://git.openstack.org/cgit/openstack/sahara/commit/?id=c7a009805e43a639f2292f6878351580e64cdead
Submitter: Jenkins
Branch: master

commit c7a009805e43a639f2292f6878351580e64cdead
Author: Sergey Lukjanov <email address hidden>
Date: Tue Mar 25 13:28:26 2014 +0400

    Fix db management: don't autocreate db on start

    We should use sahara-db-manage for db creation instead of auto created
    db schema from metadata. This approach was applied by adding support for
    alembic-based migrations and db autocreation code was removed in
    I14a0602bb34bf09086428766cb681345191436fe, but it one more place where
    we're autocreating db was missed, so, it's a fix for this issue.

    Additionally, cleanup custom hacking check for sahara.db calls.
    Docs already contains notes about need for using sahara-db-manage for
    database creation.

    Note: The main driver in fixing this right now is that if a user create
    database from metadata, he will not be able to migrate from Icehouse to
    Juno. Only databases created by alembic could be migrated to the later
    version.

    Closes-Bug: #1300190
    Change-Id: I991aa3402f658999735ad9607544251a6ef0e122