Current Series Release Notes

New Features

  • Add --force option to the nova-manage placement heal_allocations command to forcefully heal allocations for a specific instance.

  • The libvirt RBD image backend module can now handle a Glance multistore environment where multiple RBD clusters are in use across a single Nova/Glance deployment, configured as independent Glance stores. In the case where an instance is booted with an image that does not exist in the RBD cluster that Nova is configured to use, Nova can ask Glance to copy the image from whatever store it is currently in to the one that represents its RBD cluster. To enable this feature, set [libvirt]/images_rbd_glance_store_name to tell Nova the Glance store name of the RBD cluster it uses.

  • A new configuration option, [DEFAULT]/max_concurrent_snapshots, has been added. This allow operator to configure maximum concurrent snapshots on a compute host and prevent resource overuse related to snapshot.

  • Added params [libvirt]/rbd_destroy_volume_retries, defaulting to 12, and [libvirt]/rbd_destroy_volume_retry_interval, defaulting to 5, that Nova will use when trying to remove a volume from Ceph in a retry loop that combines these parameters together. Thus, maximum elapsing time is by default 60 seconds.

Upgrade Notes

  • When using file-backed memory, the nova-compute service will now fail to start if the amount of reserved memory configured using [DEFAULT] reserved_host_memory_mb is equal to or greater than the total amount of memory configured using [libvirt] file_backed_memory. Where reserved memory is less than the total amount of memory configured, a warning will be raised. This warning will become an error in a future release.

    The former combination is invalid as it would suggest reserved memory is greater than total memory available, while the latter is considered incorrect behavior as reserving of file-backed memory can and should be achieved by reducing the filespace allocated as memory by modifying [libvirt] file_backed_memory.

  • Previously, the number of concurrent snapshots was unlimited, now it is limited via [DEFAULT]/max_concurrent_snapshots, which currently defaults to 5.

  • Support for hooks has been removed. In previous versions of nova, these provided a mechanism to extend nova with custom code through a plugin mechanism. However, they were deprecated in 13.0.0 (Mitaka) as unmaintainable long-term. Versioned notifications and vendordata should be used instead. For more information, refer to this thread.

  • The entry point hook has been removed, per the deprecation announcement in the 17.0.0 (Queens) release.

Bug Fixes

  • Since Libvirt v.1.12.0 and the introduction of the libvirt issue , there is a fact that if we set cache mode whose write semantic is not O_DIRECT (i.e. “unsafe”, “writeback” or “writethrough”), there will be a problem with the volume drivers (i.e. LibvirtISCSIVolumeDriver, LibvirtNFSVolumeDriver and so on), which designate native io explicitly.

    When the driver_cache (default is none) has been configured as neither “none” nor “directsync”, the libvirt driver will ensure the driver_io to be “threads” to avoid an instance spawning failure.

  • Add support for the hw:hide_hypervisor_id extra spec. This is an alias for the hide_hypervisor_id extra spec, which was not compatible with the AggregateInstanceExtraSpecsFilter scheduler filter. See bug 1841932 for more details.

  • This release contains a fix for bug 1874032 which delegates snapshot upload into a dedicated thread. This ensures nova compute service stability on busy environment during snapshot, when concurrent snapshots or any other tasks slow down storage performance.

  • A new [workarounds]/reserve_disk_resource_for_image_cache config option was added to fix the bug 1878024 where the images in the compute image cache overallocate the local disk. If this new config is set then the libvirt driver will reserve DISK_GB resources in placement based on the actual disk usage of the image cache.

  • Previously, attempting to configure an instance with the e1000e or legacy VirtualE1000e VIF types on a host using the QEMU/KVM driver would result in an incorrect UnsupportedHardware exception. These interfaces are now correctly marked as supported.

  • Previously, it was possible to specify values for the hw:cpu_realtime_mask extra spec that were not within the range of valid instances cores. This value is now correctly validated.

  • Nova tries to remove a volume from Ceph in a retry loop of 10 attempts at 1 second intervals, totaling 10 seconds overall - which, due to 30 second ceph watcher timeout, might result in intermittent object removal failures on Ceph side (bug 1856845). Setting default values for [libvirt]/rbd_destroy_volume_retries to 12 and [libvirt]/rbd_destroy_volume_retry_interval to 5, now gives Ceph reasonable amount of time to complete the operation successfully.