Appendix B: OpenStack Upgrades
This document outlines approaches to upgrading OpenStack using the charms.
Definitions and Terms
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.
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.
All procedures outlined below should be tested in a non-production environment first.
The charms support triggering a multi-release upgrade and will handle stepping through the upgrade. However, given that some OpenStack projects (including Nova) only support there being a single release difference between components this is not recommended.
1. Charm Upgrades
All charms should be upgraded to the latest stable release 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'
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|
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 injuju status* or run:
juju run --application application-name is-leader
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
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
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.