update_network_postcommit is being called from delete_network_precommit with an open session

[Daniel Alvarez]

When a network is deleted, its segments are also deleted [0]. For each segment, it will notify about resources.SEGMENT and events.AFTER_DELETE [1] which will turn out in calling update_network_postcommit [2].

This should be avoided since drivers expect their postcommit methods to be called with no open sessions to the database. There should be separate callbacks for segments so that there's no transactions opened to the database in any of the postcommit calls.

We detected this in networking-ovn driver because we're attempting to bump revision numbers in a separate table in Neutron database when a network is updated but we can't commit that change to the database because there's already an open session on a network delete operation. This may be affecting other drivers as well.

[0] https://github.com/openstack/neutron/blob/6cdd079f8f3e6994734fa806b3c819cecb5f521a/neutron/services/segments/db.py#L315
[1] https://github.com/openstack/neutron/blob/6cdd079f8f3e6994734fa806b3c819cecb5f521a/neutron/services/segments/db.py#L178
[2] https://github.com/openstack/neutron/blob/6cdd079f8f3e6994734fa806b3c819cecb5f521a/neutron/plugins/ml2/plugin.py#L1917

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/neutron/+/852885

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/neutron/+/852885
Committed: https://opendev.org/openstack/neutron/commit/3202a5c19ec01dfd38c4471be21002467bc0a0e5
Submitter: "Zuul (22348)"
Branch: master

commit 3202a5c19ec01dfd38c4471be21002467bc0a0e5
Author: Rodolfo Alonso Hernandez <email address hidden>
Date: Wed Aug 10 12:02:50 2022 +0200

    [OVN] Remove session check in ``update_network_postcommit``

    Since [1], when a segment is deleted because the network is before,
    the segment event handler method ``_handle_segment_change`` does not
    call ``_notify_mechanism_driver_for_segment_change`` and thus the
    check performed in ``OVNMechanismDriver.update_network_postcommit``
    is not needed anymore.

    [1]https://review.opendev.org/c/openstack/neutron/+/786373

    Closes-Bug: #1739798
    Change-Id: I4bb22a0a0a233609a4d23af55a050356049eb214

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/yoga
Review: https://review.opendev.org/c/openstack/neutron/+/854233

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/xena
Review: https://review.opendev.org/c/openstack/neutron/+/854234

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/neutron/+/854234
Committed: https://opendev.org/openstack/neutron/commit/1850646b412fedb073189619142d21fe1ce45e78
Submitter: "Zuul (22348)"
Branch: stable/xena

commit 1850646b412fedb073189619142d21fe1ce45e78
Author: Rodolfo Alonso Hernandez <email address hidden>
Date: Wed Aug 10 12:02:50 2022 +0200

    [OVN] Remove session check in ``update_network_postcommit``

    Since [1], when a segment is deleted because the network is before,
    the segment event handler method ``_handle_segment_change`` does not
    call ``_notify_mechanism_driver_for_segment_change`` and thus the
    check performed in ``OVNMechanismDriver.update_network_postcommit``
    is not needed anymore.

    [1]https://review.opendev.org/c/openstack/neutron/+/786373

    Conflicts:
        neutron/plugins/ml2/drivers/ovn/mech_driver/mech_driver.py

    Closes-Bug: #1739798
    Change-Id: I4bb22a0a0a233609a4d23af55a050356049eb214
    (cherry picked from commit 3202a5c19ec01dfd38c4471be21002467bc0a0e5)
    (cherry picked from commit 921d9a79aacf8529704b83ab64ab6167bb584f3c)

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/neutron/+/854233
Committed: https://opendev.org/openstack/neutron/commit/602c1025cd4104fe6ca87704427b09bdf7d11974
Submitter: "Zuul (22348)"
Branch: stable/yoga

commit 602c1025cd4104fe6ca87704427b09bdf7d11974
Author: Rodolfo Alonso Hernandez <email address hidden>
Date: Wed Aug 10 12:02:50 2022 +0200

    [OVN] Remove session check in ``update_network_postcommit``

    Since [1], when a segment is deleted because the network is before,
    the segment event handler method ``_handle_segment_change`` does not
    call ``_notify_mechanism_driver_for_segment_change`` and thus the
    check performed in ``OVNMechanismDriver.update_network_postcommit``
    is not needed anymore.

    [1]https://review.opendev.org/c/openstack/neutron/+/786373

    Conflicts:
        neutron/plugins/ml2/drivers/ovn/mech_driver/mech_driver.py

    Closes-Bug: #1739798
    Change-Id: I4bb22a0a0a233609a4d23af55a050356049eb214
    (cherry picked from commit 3202a5c19ec01dfd38c4471be21002467bc0a0e5)

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/neutron 21.0.0.0rc1 release candidate.

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/neutron 19.5.0 release.

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/neutron 20.3.0 release.