Incorrect pass exception with oslo_db.enginefacade

[Pavel Kholkin]

After ignore and pass exception the following exception could happen:

sqlalchemy.exc.InvalidRequestError: This Session's transaction has been rolled back due to a previous exception during flush. To begin a new transaction with this Session, first issue Session.rollback(). Original exception was: (sqlite3.IntegrityError) UNIQUE constraint failed: instance_info_caches.instance_uuid

We are in a transaction, we can't have an integrity failure in a transaction, and then just continue working, we need to use a savepoint.

The problem could be reproduced e.g. in instance_info_cache_update but also could happen in other similar places where we pass an db exception.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/250790

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/250790
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=4dbf1decf91f208b15805983fb4d6de5ccafe74a
Submitter: Jenkins
Branch: master

commit 4dbf1decf91f208b15805983fb4d6de5ccafe74a
Author: Pavel Kholkin <email address hidden>
Date: Fri Nov 27 15:34:34 2015 +0300

    bug and tests in 'instance_info_cache'

    Added unit tests for 'instance_info_cache' db section,
    fixed incorrect behaviour with ignoring exception that relates
    to introducing oslo.db enginefacade.

    Closes-Bug: #1520563
    Closes-Bug: #1520567

    Co-Authored-By: Sergey Nikitin <email address hidden>

    Change-Id: I35ec688d7b176e0cb0b9ce6bd0c241b6631422c5

[Doug Hellmann (doug-hellmann)]

This issue was fixed in the openstack/nova 13.0.0.0b3 development milestone.