Current Series Release Notes

New Features

  • A --task-log option has been added to the nova-manage db archive_deleted_rows CLI. When --task-log is specified, task_log table records will be archived while archiving the database. The --task-log option works in conjunction with --before if operators desire archiving only records that are older than <date>. The updated_at field is used by --task-log --before <date> to determine the age of a task_log record for archival.

    The task_log database table contains instance usage audit records if nova-compute has been configured with [DEFAULT]instance_usage_audit = True. This will be the case if OpenStack Telemetry is being used in the deployment, as the option causes Nova to generate audit data that Telemetry then retrieves from the server usage audit log API [1].

    Historically, there has been no way to delete task_log table records other than manual database modification. Because of this, task_log records could pile up over time and operators are forced to perform manual steps to periodically truncate the task_log table.


Upgrade Notes

  • As part of the fix for bug 1910466, code that attempted to optimize VM CPU thread assignment based on the host CPU topology as it was determined to be buggy, undocumented and rejected valid virtual CPU topologies while also producing different behavior when CPU pinning was enabled vs disabled. The optimization may be reintroduced in the future with a more generic implementation that works for both pinned and unpinned VMs.

Security Issues

  • A vulnerability in the console proxies (novnc, serial, spice) that allowed open redirection has been patched. The novnc, serial, and spice console proxies are implemented as websockify servers and the request handler inherits from the python standard SimpleHTTPRequestHandler. There is a known issue in the SimpleHTTPRequestHandler which allows open redirects by way of URLs in the following format:

    which if visited, will redirect a user to

    The novnc, serial, and spice console proxies will now reject requests that pass a redirection URL beginning with “//” with a 400 Bad Request.

  • In this release OVS port creation has been delegated to os-vif when the noop or openvswitch security group firewall drivers are enabled in Neutron. Those options, and others that disable the hybrid_plug mechanism, will now use os-vif instead of libvirt to plug VIFs into the bridge. By delegating port plugging to os-vif we can use the isolate_vif config option to ensure VIFs are plugged securely preventing guests from accessing other tenants’ networks before the neutron ovs agent can wire up the port. See bug #1734320 for details. Note that OVN, ODL and other SDN solutions also use hybrid_plug=false but they are not known to be affected by the security issue caused by the previous behavior. As such the isolate_vif os-vif config option is only used when deploying with ml2/ovs.

Bug Fixes

  • Improved detection of anti-affinity policy violation when performing live and cold migrations. Most of the violations caused by race conditions due to performing concurrent live or cold migrations should now be addressed by extra checks in the compute service. Upon detection, cold migration operations are automatically rescheduled, while live migrations have two checks and will be rescheduled if detected by the first one, otherwise the live migration will fail cleanly and revert the instance state back to its previous value.

  • Bug 1851545, wherein unshelving an instance with SRIOV Neutron ports did not update the port binding’s pci_slot and could cause libvirt PCI conflicts, has been fixed.


    Constraints in the fix’s implementation mean that it only applies to instances booted after it has been applied. Existing instances will still experience bug 1851545 after being shelved and unshelved, even with the fix applied.

  • The nova libvirt driver supports two independent features, virtual CPU topologies and virtual NUMA topologies. Previously, when hw:cpu_max_sockets, hw:cpu_max_cores and hw:cpu_max_threads were specified for pinned instances (hw:cpu_policy=dedicated) without explicit hw:cpu_sockets, hw:cpu_cores, hw:cpu_threads extra specs or their image equivalent, nova failed to generate a valid virtual CPU topology. This has now been fixed and it is now possible to use max CPU constraints with pinned instances. e.g. a combination of hw:numa_nodes=2, hw:cpu_max_sockets=2, hw:cpu_max_cores=2, hw:cpu_max_threads=8 and hw:cpu_policy=dedicated can now generate a valid topology using a flavor with 8 vCPUs.

  • In this release we delegate port plugging to os-vif for all OVS interface types. This allows os-vif to create the OVS port before libvirt creates a tap device during a live migration therefore preventing the loss of the MAC learning frames generated by QEMU. This resolves a long-standing race condition between Libvirt creating the OVS port, Neutron wiring up the OVS port and QEMU generating RARP packets to populate the vswitch MAC learning table. As a result this reduces the interval during a live migration where packets can be lost. See bug #1815989 for details.

  • To fix device detach issues in the libvirt driver the detach logic has been changed from a sleep based retry loop to waiting for libvirt domain events. During this change we also introduced two new config options to allow fine tuning the retry logic. For details see the description of the new [libvirt]device_detach_attempts and [libvirt]device_detach_timeout config options.