Appendix B: OpenStack Upgrades

Appendix B: OpenStack Upgrades

Overview

This document outlines approaches to upgrading OpenStack using the charms.

Definitions and Terms

Charm Upgrade

This is an upgrade of the charm software which is used to deploy and manage OpenStack. This will include charms that manage applications which are not part of the OpenStack project such as Rabbitmq and MySQL.

OpenStack Upgrade

This is an upgrade of the OpenStack software (packages) that are installed and managed by the charms.

Ubuntu Server Package Upgrade

This is an upgrade of the Ubuntu packages on the server that are not part of the OpenStack project such as kernel modules, QEMU binaries, KVM kernel module etc.

Ubuntu Release Upgrade

This is an upgrade from one Ubuntu release to the next.

Testing

All procedures outlined below should be tested in a non-production environment first.

Skipping Releases or Fast Forward Upgrade

The charms support stepped OpenStack version upgrades (N+1). For example: Ocata to Pike, then Pike to Queens, Queens to Rocky and so on.

This stepped N+1 approach in charms is mature, well-tested, and can be used back-to-back to achieve N+N upgrade results.

Skipping releases is not supported by many upstream OpenStack projects, and it is not supported by the charms.

“Fast-forward-upgrade” is also not supported by the charms. FFU/FFWD is an upgrade approach where the control plane services are stepped through N+1+1+1 upgrades, typically to achieve an N+3 upgrade result.

1. Charm Upgrades

All charms should be upgraded to the latest stable charm revision before performing an OpenStack upgrade. It is recommended to upgrade the Keystone charm first. The order of upgrading subsequent charms is usually not important but check the release notes for each release to ensure there are no special requirements.

To upgrade a charm that was deployed from the charm store:

juju upgrade-charm <charm name>

The progress of the upgrade can be monitored by checking the workload status of the charm which can been with juju status. Once the upgrade is complete the charm status should contain the message ‘Unit is ready’. The version of the deployed software can also been seen from juju status:

juju status
...
App       Version  Status  Scale  Charm      Store  Rev  OS      Notes
keystone  11.0.3   active      1  keystone   local  0  ubuntu
...

This shows that the deployed version of keystone is 11.0.3 (Ocata)

If the Juju controller is resource constrained it may be beneficial to do the charm upgrades in series rather than in parallel. After each charm upgrade check for any unforeseen errors reported in juju status before proceeding.

2. Pre-Upgrade Tasks

2.1 Release Notes

Check the release notes for the charm releases for any special instructions.

2.2 Check current deployment

Check for any charm errors in juju status. If a monitor is in use like Nagios then make sure any alerts have been cleared before proceeding. This is to ensure that alerts after the upgrade are not pre-existing problems.

Also ensure that the current charms must not do not contain any customisations since that is not supported and they will be overwritten by the upgrade.

2.3 Database row archiving

During the upgrade, database migrations will be run. These can be significantly sped up by archiving any stale data (such as deleted instances). To perform the archive of nova data run the nova-cloud-controller action:

juju run-action nova-cloud-controller/0 archive-data

This action may need to be run multiple times until the action output reports ‘Nothing was archived’

2.4 Purge old compute service entries

Old service entries for compute services on units which are no longer part of the model should be purged before upgrade.

Any old service entries will show as ‘down’ and on machines no longer in the model when looking at the current list of compute services:

openstack compute service list

Services can be removed using the ‘compute service delete’ command:

openstack compute service delete <ID of service>

3. Upgrade Order

The charms are grouped together below. The ordering of upgrade within a group does not matter but all the charms in each group should be upgraded before moving on to the next group. Any release note guidance overrides the order listed here.

Group Charm Name Charm Type
1 keystone Core Identity
2 ceph-mon Storage
2 ceph-osd Storage
2 ceph-fs Storage
2 ceph-radosgw Storage
2 swift-proxy Storage
2 swift-storage Storage
3 aodh Control Plane
3 barbican Control Plane
3 ceilometer Control Plane
3 cinder Control Plane
3 designate Control Plane
3 designate-bind Control Plane
3 glance Control Plane
3 gnocchi Control Plane
3 heat Control Plane
3 manila Control Plane
3 manila-generic Control Plane
3 neutron-api Control Plane
3 neutron-gateway Control Plane
3 nova-cloud-controller Control Plane
3 openstack-dashboard Control Plane
4 nova-compute Compute

4. Performing The Upgrade

If the service to be upgraded is in a highly-available cluster then the best way to minimise service interruption is to follow the “HA with pause/resume” instructions below. If there are multiple units of the service but they are not clustered then follow the “Action managed” instructions. Finally, if there is a single unit then follow “Application one-shot”.

Some parts of the upgrade, like database migrations, only need to run once per application and these tasks are handled by the lead unit. It is advisable that these tasks are run first (this is not applicable for one-shot deployments). To achieve this run the upgrade on the lead unit first. To check which unit is the lead unit either check which unit has a ‘*’ next to it in juju status or run:

juju run --application application-name is-leader

Warning

Extra care must be taken when performing OpenStack upgrades in an environment with a converged architecture. If two principle charms have been placed on the same unit (e.g. nova-compute and ceph-osd), then upgrading one of the charms will cause the underlying system to be updated to point at packages from the next Openstack release. If the machine has unattended-upgrades enabled, which is the default in xenial and bionic, the second charm may have its packages updated outside of juju’s control. We recommend disabling unattended upgrades for the duration of the upgrade process, and to renable unattended-upgrades once complete.

HA with pause/resume

The majority of charms support pause and resume actions. These actions can be used to place units of a charm into a state where maintenance operations can be carried out. Using these actions along with action managed upgrades allows a charm to be removed from service, upgraded and returned to service.

For example to upgrade a three node nova-cloud-controller service from Ocata to Pike where nova-cloud-controller/2 is the leader:

juju config nova-cloud-controller action-managed-upgrade=True
juju config nova-cloud-controller openstack-origin='cloud:xenial-pike'
juju run-action nova-cloud-controller/2 --wait pause
juju run-action nova-cloud-controller/2 --wait openstack-upgrade
juju run-action nova-cloud-controller/2 --wait resume
juju run-action nova-cloud-controller/1 --wait pause
juju run-action nova-cloud-controller/1 --wait openstack-upgrade
juju run-action nova-cloud-controller/1 --wait resume
juju run-action nova-cloud-controller/0 --wait pause
juju run-action nova-cloud-controller/0 --wait openstack-upgrade
juju run-action nova-cloud-controller/0 --wait resume

Action managed

If there are multiple units of an application then each unit can be upgraded one at a time using Juju actions. This allows for rolling upgrades. To use this feature the charm configuration option action-managed-upgrade must be set to True.

For example to upgrade a three node keystone service from Ocata to Pike where keystone/1 is the leader:

juju config keystone action-managed-upgrade=True
juju config keystone openstack-origin='cloud:xenial-pike'
juju run-action keystone/1 --wait openstack-upgrade
juju run-action keystone/0 --wait openstack-upgrade
juju run-action keystone/2 --wait openstack-upgrade

Application one-shot

This is the simplest and quickest way to perform the upgrade. Using this method will cause all the units in the application to be upgraded at the same time. This is likely to cause a service outage while the upgrade completes. If there is only one unit in the application then this is the only option.

juju config keystone openstack-origin='cloud:xenial-pike'

5. Post-Upgrade Tasks

Check juju status and any monitoring solution for errors.

Known Issues to be aware of during Upgrades

Before doing an OpenStack upgrade (rather than a charm upgrade), the release notes for the original and target versions of OpenStack should be read. In particular pay attention to services or configuration parameters that have retired, deprecated or changed. Wherever possible, the latest version of a charm has code to handle almost all changes such that the resultant system should be configured in the same way. However, removed, added or replaced services will require manual intervention.

When charms can’t perform a change, either due to a bug in the charm (i.e. a system configuration that the charms haven’t been programmed to handle) or because at the individual charm level the charm can’t change the service (i.e. when a service is replaced with another service, a different charm would be needed).

However, the following list is known issues that an operator may encounter that the charm does not automatically take care of, along with mitigation strategies to resolve the situation.

neutron-gateway charm: upgrading from Mikata to Newton

Reference Bug #1809190: switching from external-network-id and external-port to data-port and bridge-mappings does not remove incorrect nics from bridges

Between the mitaka and newton OpenStack releases, the neutron-gateway charm add two options, bridge-mappings and data-port, which replaced the (now) deprecated ext-port option. This was to provide more control over how neutron-gateway can configure external networking.

The charm was designed so that it would work with either data-port (no longer recommended) or bridge-mappings and data-port. Unfortunately, when upgrading from OpenStack Mitaka to Newton the referenced bug above was been encountered, and therefore may require manual intervention to resolve the issue.

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