2023.1 Series Release Notes


Upgrade Notes

  • Configuration of service user tokens is now required for all Nova services to ensure security of block-storage volume data.

    All Nova configuration files must configure the [service_user] section as described in the documentation.

    See https://bugs.launchpad.net/nova/+bug/2004555 for more details.



The OpenStack 2023.1 (Nova 27.0.0) release includes many new features and bug fixes. Please be sure to read the upgrade section which describes the required actions to upgrade your cloud from 26.0.0 (Zed) to 27.0.0 (2023.1). As a reminder, OpenStack 2023.1 is our first Skip-Level-Upgrade Release (starting from now, we name it a SLURP release) where you can rolling-upgrade your compute services from OpenStack Yoga as an experimental feature. Next SLURP release will be 2024.1.

There are a few major changes worth mentioning. This is not an exhaustive list:

  • The latest Compute API microversion supported for 2023.1 is v2.95.

  • PCI devices can now be scheduled by Nova using the Placement API on a opt-in basis. This will help the nova-scheduler service to better schedule flavors that use PCI (non-Neutron related) resources, will generate less reschedules if an instance cannot be created on a candidate and will help the nova-scheduler to not miss valid candidates if the list was too large.

  • Operators can now ask Nova to manage the power consumption of dedicated CPUs so as to either offline them or change their governor if they’re currently not in use by any instance or if the instance is stopped.

  • Nova will prevent unexpected compute service renames by persisting a unique compute UUID on local disk. This stored UUID will be considered the source of truth for knowing whether the compute service hostame has been modified or not. As a reminder, changing a compute hostname is forbidden, particularly when this compute is currently running instances on top of it.

  • SPICE consoles can now be configured with compression settings which include choices of the compression algorithm and the compression mode.

  • Fully-Qualified Domain Names are now considered valid for an instance hostname if you use the 2.94 API microversion.

  • By opting into 2.95 API microversion, evacuated instances will remain stopped on the destination host until manually started.

  • Nova APIs now by default support new RBAC policies <https://docs.openstack.org/nova/latest/configuration/policy.html> and scopes. See our Policy Concepts documention <https://docs.openstack.org/nova/latest/configuration/policy-concepts.html> for further details.

New Features

  • The following SPICE-related options are added to the spice configuration group of a Nova configuration:

    • image_compression

    • jpeg_compression

    • zlib_compression

    • playback_compression

    • streaming_mode

    These configuration options can be used to enable and set the SPICE compression settings for libvirt (QEMU/KVM) provisioned instances. Each configuration option is optional and can be set explictly to configure the associated SPICE compression setting for libvirt. If all configuration options are not set, then none of the SPICE compression settings will be configured for libvirt, which corresponds to the behavior before this change. In this case, the built-in defaults from the libvirt backend (e.g. QEMU) are used.

    Note that those options are only taken into account if SPICE support is enabled (and the VNC support is disabled).

  • Starting with v2.95 any evacuated instance will be stopped at destination. The required minimum version for Nova computes is 27.0.0 (antelope 2023.1). Operator can still continue using previous behavior by selecting microversion below v2.95.

  • This is now possible to configure nova-compute services using libvirt driver by setting [libvirt]cpu_power_management to True in order to let the service to powering down or up physical CPUs depending on whether those CPUs are pinned or not to instances. In order on to support this feature, the compute service needs to be set with [compute]cpu_dedicated_set. If so, all the related CPUs will be powering down until they are used by an instance where the related pinned CPU will be powering up just before starting the guest. If [compute]cpu_dedicated_set isn’t set, then the compute service will refuse to start. By default the power strategy will offline CPUs when powering down and online the CPUs on powering up but another strategy is possible by using [libvirt]cpu_power_management_strategy=governor which will rather modify the related CPU governor using [libvirt]cpu_power_governor_low and [libvirt]cpu_power_governor_high configuration values (respective defaults being powersave and performance)

  • Since 26.0.0 (Zed) Nova supports tracking PCI devices in Placement. Now Nova also supports scheduling flavor based PCI device requests via Placement. This support is disable by default. Please read documentation for more details on what is supported how this feature can be enabled.

  • The 2.94 microversion has been added. This microversion extends microversion 2.90 by allowing Fully Qualified Domain Names (FQDN) wherever the hostname is able to be specified. This consists of creating an instance (POST /servers), updating an instance (PUT /servers/{id}), or rebuilding an instance (POST /servers/{server_id}/action (rebuild)). When using an FQDN as the instance hostname, the [api]dhcp_domain configuration option must be set to the empty string in order for the correct FQDN to appear in the hostname field in the metadata API.

  • The compute manager now uses a local file to provide node uuid persistence to guard against problems with renamed services, among other things. Deployers wishing to ensure that new compute services get a predicatble uuid before initial startup may provision that file and nova will use it, otherwise nova will generate and write one to a compute_id file in CONF.state_path the first time it starts up. Accidental renames of a compute node’s hostname will be detected and the manager will exit to avoid database corruption. Note that none of this applies to Ironic computes, as they manage nodes and uuids differently.

  • Guru Meditation Reports can now be generated for the Nova API service when running under uWSGI. Note that uWSGI intercepts SIGUSR2 signals, so a file trigger should be used instead.

Upgrade Notes

  • Operators will have to consider upgrading compute hosts to Nova 27.0.0 (antelope 2023.1) in order to take advantage of the new (microversion v2.95) evacuate API behavior. An exception will be raised for older versions.

  • The Nova service enable the API policies (RBAC) new defaults and scope by default. The Default value of config options [oslo_policy] enforce_scope and [oslo_policy] oslo_policy.enforce_new_defaults have been changed to True.

    This means if you are using system scope token to access Nova API then the request will be failed with 403 error code. Also, new defaults will be enforced by default. To know about the new defaults of each policy rule, refer to the Policy New Defaults. For more detail about the Nova API policies changes, refer to Policy Concepts.

    If you want to disable them then modify the below config options value in nova.conf file:

  • In order to make use of microversion’s 2.94 FQDN hostnames, the [api]dhcp_domain config option must be set to the empty string. If this is not done, the hostname field in the metadata API will be incorrect, as it will include the value of [api]dhcp_domain appended to the instance’s FQDN. Note that simply not setting [api]dhcp_domain is not enough, as it has a default value of novalocal. It must explicitly be set to the empty string.

  • Existing compute nodes will, upon upgrade, perist the uuid of the compute node assigned to their hostname at first startup. Since this must match what is currently in the database, it is important to let nova provision this file from its database. Nova will only persist to a compute_id file in the CONF.state_path directory, which should already be writable.

  • In this release the default values for the initial ram and cpu allocation ratios have been updated to 1.0 and 4.0 respectively. This will not affect any existing compute node resource providers but the new default will take effect on the creation of new resource providers.

Bug Fixes

  • Fixes bug 1996995 in which VMs live migrated on certain VXLAN Arista network fabrics were inaccessible until the switch arp cache expired.

    A Nova workaround option of enable_qemu_monitor_announce_self was added to fix bug 1815989 which when enabled would interact with the QEMU monitor and force a VM to announce itself.

    On certain network fabrics, VMs that are live migrated remain inaccessible via the network despite the QEMU monitor announce_self command successfully being called.

    It was noted that on Arista VXLAN fabrics, testing showed that it required several attempts of running the QEMU announce_self monitor command before the switch would acknowledge a VM’s new location on the fabric.

    This fix introduces two operator configurable options. The first option sets the number of times the QEMU monitor announce_self command is called - qemu_announce_self_count

    The second option allows operators to set the delay between the QEMU announce_self commands in seconds for subsequent announce_self commands with qemu_announce_self_interval

  • Fixed when placement returns ironic nodes that have just started automatic cleaning as possible valid candidates. This is done by marking all ironic nodes with an instance on them as reserved, such that nova only makes them available once we have double checked Ironic reports the node as available. If you don’t have automatic cleaning on, this might mean it takes longer than normal for Ironic nodes to become available for new instances. If you want the old behaviour use the following workaround config: [workarounds]skip_reserve_in_use_ironic_nodes=true

  • apache mod_wsgi does not support passing commandline arguments to the wsgi application that it hosts. As a result when the nova api or metadata api where run under mod_wsgi it was not posible to use multiple config files or non-default file names i.e. nova-api.conf This has been adressed by the intoduction of a new, optional, envionment varible OS_NOVA_CONFIG_FILES. OS_NOVA_CONFIG_FILES is a ; seperated list fo file path relitive to OS_NOVA_CONFIG_DIR. When unset the default api-paste.ini and nova.conf will be used form /etc/nova. This is supported for the nova api and nova metadata wsgi applications.

  • Fix rescuing volume based instance by adding a check for ‘hw_rescue_disk’ and ‘hw_rescue_device’ properties in image metadata before attempting to rescue instance.

  • Nova’s use of libvirt’s compareCPU() API has become error-prone as it doesn’t take into account host hypervisor’s capabilities. With QEMU >=2.9 and libvirt >= 4.4.0, libvirt will do the right thing in terms of CPU comparison checks via a new replacement API, compareHypervisorCPU(). Nova satisfies the said minimum version requirements of QEMU and libvirt by a good margin.

    This change replaces the usage of older API, compareCPU(), with the new one, compareHypervisorCPU().

Other Notes

  • For networks which have any subnets with enabled DHCP, MTU value is not send in the metadata. In such case MTU is configured through the DHCP server.

  • A workaround has been added to the libvirt driver to catch and pass migrations that were previously failing with the error:

    libvirt.libvirtError: internal error: migration was active, but no RAM info was set

    See bug 1982284 for more details.

  • The default initial allocation ratios enabled ram over commit by default with a factor of 1.5. This value was chosen early in nova’s history as the predominant workload was web hosting or other light weight virtualization. Similarly the default initial cpu allocation ratio defaulted to 16. As more demanding workload from telco, enterprise, scientific and governmental users became the norm the initial values we had chosen became less and less correct overtime. These have now been updated to reflect a more reasonable default for the majority of our users. As of this release the initial ram allocation value is 1.0 disabling overcommit by default for new compute nodes and the initial cpu allocation ratio is now 4.0 which is a more reasonable overcommit for non idle workloads.