Separate use of database sessions
This patch separates the use of database session in different MBS components
and do not mix them together.
In general, MBS components could be separated as the REST API (implemented
based on Flask) and non-REST API including the backend build workflow
(implemented as a fedmsg consumer on top of fedmsg-hub and running
independently) and library shared by them. As a result, there are two kind of
database session used in MBS, one is created and managed by Flask-SQLAlchemy,
and another one is created from SQLAclhemy Session API directly. The goal of
this patch is to make ensure session object is used properly in the right
All the changes follow these rules:
* REST API related code uses the session object db.session created and
managed by Flask-SQLAlchemy.
* Non-REST API related code uses the session object created with SQLAlchemy
Session API. Function make_db_session does that.
* Shared code does not created a new session object as much as possible.
Instead, it accepts an argument db_session.
The first two rules are applicable to tests as well.
* Switch tests back to run with a file-based SQLite database.
* make_session is renamed to make_db_session and SQLAlchemy connection pool
options are applied for PostgreSQL backend.
* Frontend Flask related code uses db.session
* Shared code by REST API and backend build workflow accepts SQLAlchemy session
object as an argument. For example, resolver class is constructed with a
database session, and some functions accepts an argument for database session.
* Build workflow related code use session object returned from make_db_session
and ensure db.session is not used.
* Only tests for views use db.session, and other tests use db_session fixture
to access database.
* All argument name session, that is for database access, are renamed to
* Functions model_tests_init_data, reuse_component_init_data and
reuse_shared_userspace_init_data, which creates fixture data for
tests, are converted into pytest fixtures from original function
called inside setup_method or a test method. The reason of this
conversion is to use fixture ``db_session`` rather than create a
new one. That would also benefit the whole test suite to reduce the
number of SQLAlchemy session objects.
Signed-off-by: Chenxiong Qi <email@example.com>