Comment 39 for bug 1853009

Reviewed: https://review.opendev.org/c/openstack/nova/+/811809
Committed: https://opendev.org/openstack/nova/commit/665c053315439e1345aa131f4839945d662fb3f3
Submitter: "Zuul (22348)"
Branch: stable/wallaby

commit 665c053315439e1345aa131f4839945d662fb3f3
Author: Mark Goddard <email address hidden>
Date: Wed Nov 20 12:01:33 2019 +0000

    Fix inactive session error in compute node creation

    In the fix for bug 1839560 [1][2], soft-deleted compute nodes may be
    restored, to ensure we can reuse ironic node UUIDs as compute node
    UUIDs. While this seems to largely work, it results in some nasty errors
    being generated [3]:

        InvalidRequestError This session is in 'inactive' state, due to the
        SQL transaction being rolled back; no further SQL can be emitted
        within this transaction.

    This happens because compute_node_create is decorated with
    pick_context_manager_writer, which begins a transaction. While
    _compute_node_get_and_update_deleted claims that calling a second
    pick_context_manager_writer decorated function will begin a new
    subtransaction, this does not appear to be the case.

    This change removes pick_context_manager_writer from the
    compute_node_create function, and adds a new _compute_node_create
    function which ensures the transaction is finished if
    _compute_node_get_and_update_deleted is called.

    The new unit test added here fails without this change.

    This change marks the removal of the final FIXME from the functional
    test added in [4].

    [1] https://bugs.launchpad.net/nova/+bug/1839560
    [2] https://git.openstack.org/cgit/openstack/nova/commit/?id=89dd74ac7f1028daadf86cb18948e27fe9d1d411
    [3] http://paste.openstack.org/show/786350/
    [4] https://review.opendev.org/#/c/695012/

    Conflicts:
        nova/db/sqlalchemy/api.py

    NOTE(melwitt): The conflict is because change
    I9f414cf831316b624132d9e06192f1ecbbd3dd78 (db: Copy docs from
    'nova.db.*' to 'nova.db.sqlalchemy.*') is not in Wallaby.

    NOTE(melwitt): Difference from the cherry picked change from calling
    nova.db.api => nova.db.sqlalchemy.api directly are due to the alembic
    migration in Xena which looks to have made the nova.db.api interface
    obsolete.

    Change-Id: Iae119ea8776bc7f2e5dbe2e502a743217beded73
    Closes-Bug: #1853159
    Related-Bug: #1853009
    (cherry picked from commit 2383cbb4a518821d245fce316b3778c8ba8e5246)