This looks more complicated than it is, but it's really quite simple.
Essentially we have to deal with two possible configurations:
- For existing deployments, the DB sync operation should apply any
outstanding sqlalchemy-migrate-based migrations, dummy apply the
initial alembic migration, and then apply any additional alembic-based
migrations requested (or any available, if no version is specified).
- For new deployments, the DB sync operation should apply the initial
alembic migration and any additional alembic-based migrations
requested (or any available, if no version is specified). No
sqlalchemy-migrate-based migrations will ever be applied.
While we continue to allow users to request a specific database
migration version to upgrade to, we *do not* allow them to request a
sqlalchemy-migrate-based migration version. There's no good reason to do
this - the deployment won't run with an out-of-date DB schema (something
that's also true of the alembic migration, fwiw) - and we want to get
people off of sqlalchemy-migrate as fast as possible. A change in a
future release can remove the sqlalchemy-migrate-based migrations once
we're sure that they'll have upgraded to a release including all of the
sqlalchemy-migrated-based migrations (so Wallaby).
Tests are modified to validate the sanity of these operations. They're
mostly trivial changes, but we do need to do some funky things to ensure
that (a) we don't use logger configuration from 'alembic.ini' that will
mess with our existing logger configuration and (b) we re-use connection
objects as necessary to allow us to run tests against in-memory
databases, where a different connection would actually mean a different
database. We also can't rely on 'WalkVersionsMixin' from oslo.db since
that only supports sqlalchemy-migrate [1]. We instead must re-invent the
wheel here somewhat.
[1] https://github.com/openstack/oslo.db/blob/10.0.0/oslo_db/sqlalchemy/test_migrations.py#L42-L44
Change-Id: I850af601f81bd5d2ecc029682ae10d3a07c936ce
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>
905c9723e9