instance_create() DB API method implicitly creates additional DB transactions

[Roman Podoliaka]

In DB API code we have a notion of 'public' and 'private' methods. The former are conceptually executed within a *single* DB transaction and the latter can either create a new transaction or participate in the existing one. The whole point is to be able to roll back the results of DB API methods easily and be able to retry method calls on connection failures. We had a bp (https://blueprints.launchpad.net/nova/+spec/db-session-cleanup) in which all DB API have been re-factored to maintain these properties.

instance_create() is one of the methods that currently violates the rules of 'public' DB API methods and creates a concurrent transaction implicitly.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/115255
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=dbc46b99cc85402c087bb214c120bce2c65dfea9
Submitter: Jenkins
Branch: master

commit dbc46b99cc85402c087bb214c120bce2c65dfea9
Author: Roman Podoliaka <email address hidden>
Date: Tue Aug 19 14:05:50 2014 +0300

    Add _security_group_ensure_default() DBAPI method

    According to the convention we use for DB API methods, every public
    method should have a private counterpart. The difference between
    those two is that the latter accepts an optional 'session' argument,
    which makes it possible for the method to participate in the existing
    database transaction.

    security_group_ensure_default() was called inside instance_create()
    and thus implicitly created a new concurrent db transaction, which
    is now fixed by making a call to a private counterpart and passing
    the session instance.

    Closes-Bug: #1362233

    Change-Id: Ifa1b6430328fde1ab0984f726bd8392bbd3f7ee5

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/icehouse
Review: https://review.openstack.org/134928

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/134928
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=f78165661e5ce0bd7287124b75f6c60845b9a3c1
Submitter: Jenkins
Branch: stable/icehouse

commit f78165661e5ce0bd7287124b75f6c60845b9a3c1
Author: Roman Podoliaka <email address hidden>
Date: Tue Aug 19 14:05:50 2014 +0300

    Add _security_group_ensure_default() DBAPI method

    According to the convention we use for DB API methods, every public
    method should have a private counterpart. The difference between
    those two is that the latter accepts an optional 'session' argument,
    which makes it possible for the method to participate in the existing
    database transaction.

    security_group_ensure_default() was called inside instance_create()
    and thus implicitly created a new concurrent db transaction, which
    is now fixed by making a call to a private counterpart and passing
    the session instance.

    Closes-Bug: #1362233

    Change-Id: Ifa1b6430328fde1ab0984f726bd8392bbd3f7ee5
    (cherry picked from commit dbc46b99cc85402c087bb214c120bce2c65dfea9)