Some things that were missed in previous patches and are thrown together
here:

- Add alembic as an explicit dependency (we were getting it transitively
  from oslo.db). We also bump the sqlalchemy dependency to a 1.4.x
  release, which is the minimum supported by our chosen version of
  alembic (more on this below)
- Remove tooling related to the old migrations
- Fix the tox whitelisting of the flaky MySQL tests

On the SQLAlchemy front, we opt for 1.4.13. Technically alembic should
support anything from 1.4.0, however, with SQLAlchemy >= 1.4.0, < 1.4.13
we see errors like the following in some tests:

  sqlalchemy.exc.InvalidRequestError: Entity namespace for
  "count(instance_mappings.id)" has no property "queued_for_delete"

There's nothing specific about this in the release notes for 1.4.13 [1]
but it definitely fixes things.

[1] https://docs.sqlalchemy.org/en/14/changelog/changelog_14.html#change-1.4.13

Change-Id: I4c8eb13f11aa7471c26a5ba326319aef245c9836
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

The two remaining modules, 'api_models' and 'api_migrations', are
moved to the new 'nova.db.api' module.

Change-Id: I138670fe36b07546db5518f78c657197780c5040
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

Merge these, removing an unnecessary layer of abstraction, and place
them in the new 'nova.db.main' directory. The resulting change is huge,
but it's mainly the result of 's/sqlalchemy import api/main import api/'
and 's/nova.db.api/nova.db.main.api/' with some necessary cleanup. We
also need to rework how we do the blocking of API calls since we no
longer have a 'DBAPI' object that we can monkey patch as we were doing
before. This is now done via a global variable that is set by the 'main'
function of 'nova.cmd.compute'.

The main impact of this change is that it's no longer possible to set
'[database] use_db_reconnect' and have all APIs automatically wrapped in
a DB retry. Seeing as this behavior is experimental, isn't applied to
any of the API DB methods (which don't use oslo.db's 'DBAPI' helper),
and is used explicitly in what would appear to be the critical cases
(via the explicit 'oslo_db.api.wrap_db_retry' decorator), this doesn't
seem like a huge loss.

Change-Id: Iad2e4da4546b80a016e477577d23accb2606a6e4
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

We place these in a 'legacy_migrations' directory, as we will soon be
adding alembic-based migrations in a 'migration' directory.

Change-Id: Ib927e4c48f59a467a913875111ffbf64ffe0de90
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

Only install mariadb on EL based hosts. Also when using mariadb and
postgresql on EL based distros we need to ensure each service is
configured and actually started before using either.

Co-Authored-By: Ade Lee <alee@redhat.com>
Change-Id: I7122933d85bd7d0333c2c35e0f1a8414c1baa6d5

This currently runs in the 'check' pipeline, as part of the pep8 job,
which causes otherwise perfectly valid backports to report as failing
CI. There's no reason a stable core shouldn't be encouraged to review
these patches: we simply want to prevent them *merging* before their
parent(s). Resolve this conflict by moving the check to separate voting
job in the 'gate' pipeline as well as a non-voting job in the 'check'
pipeline to catch more obvious issues.

Change-Id: Id3e4452883f6a3cf44ff58b39ded82e882e28c23
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

This tool was used while building the compact-db-migrations-wallaby
series during Wallaby [1]. It might be helpful in the future, so commit
it now.

Change-Id: Idd556fac96ce621ad095862597c4f11851852fed
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

The checks performed by this script aren't always useful to downstream
consumers of the repo so allow them to disable the script without having
to make changes to tox.ini.

Change-Id: I4f551dc4b57905cab8aa005c5680223ad1b57639

This is a follow up to change
I8e4e5afc773d53dee9c1c24951bb07a45ddc2f1a which fixed an issue with
validation when the topmost patch after a Zuul rebase is a merge
patch.

We need to also use the $commit_hash variable for the check for
stable-only patches, else it will incorrectly fail because it is
checking the merge patch's commit message.

Change-Id: Ia725346b65dd5e2f16aa049c74b45d99e22b3524

These will not be used in a world without the XenAPI driver.

Change-Id: I5bc3c7855b817c4ce2b8919c76be80cceabeec9e
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>