Upgrading Keystone

As of the Newton release, keystone supports two different approaches to upgrading across releases. The traditional approach requires a significant outage to be scheduled for the entire duration of the upgrade process. The more modern approach results in zero downtime, but is more complicated due to a longer upgrade procedure.

Note

The details of these steps are entirely dependent on the details of your specific deployment, such as your chosen application server and database management system. Use it only as a guide when implementing your own upgrade process.

Before you begin

Plan your upgrade:

  • Read and ensure you understand the release notes for the next release.
  • Resolve any outstanding deprecation warnings in your logs. Some deprecation cycles are as short as a single release, so it’s possible to break a deployment if you leave any outstanding warnings. It might be a good idea to re-read the release notes for the previous release (or two!).
  • Prepare your new configuration files, including keystone.conf, logging.conf, policy.json, keystone-paste.ini, and anything else in /etc/keystone/, by customizing the corresponding files from the next release.

Upgrading with downtime

This is a high-level description of our upgrade strategy built around keystone-manage db_sync. It assumes that you are willing to have downtime of your control plane during the upgrade process and presents minimal risk. With keystone unavailable, no other OpenStack services will be able to authenticate requests, effectively preventing the rest of the control plane from functioning normally.

  1. Stop all keystone processes. Otherwise, you’ll risk multiple releases of keystone trying to write to the database at the same time, which may result in data being inconsistently written and read.
  2. Make a backup of your database. Keystone does not support downgrading the database, so restoring from a full backup is your only option for recovery in the event of an upgrade failure.
  3. Upgrade all keystone nodes to the next release.
  4. Update your configuration files (/etc/keystone/) with those corresponding from the latest release.
  5. Run keystone-manage db_sync from any single node to upgrade both the database schema and run any corresponding database migrations.
  6. (New in Newton) Run keystone-manage doctor to diagnose symptoms of common deployment issues and receive instructions for resolving them.
  7. Start all keystone processes.

Upgrading with minimal downtime

If you run a multi-node keystone cluster that uses a replicated database, like a Galera cluster, it is possible to upgrade with minimal downtime. This method also optimizes recovery time from a failed upgrade. This section assumes familiarity with the base case (Upgrading with downtime) outlined above. In these steps the nodes will be divided into first and other nodes.

  1. Backup your database. There is no way to rollback the upgrade of keystone and this is your worst-case fallback option.
  2. Disable keystone on all nodes but the first node. This can be done via a variety of mechanisms that will depend on the deployment. If you are unable to disable a service or place a service into maintenance mode in your load balancer, you can stop the keystone processes.
  3. Stop the database service on one of the other nodes in the cluster. This will isolate the old dataset on a single node in the cluster. In the event of a failed update this data can be used to rebuild the cluster without having to restore from backup.
  4. Update the configuration files on the first node.
  5. Upgrade keystone on the first node. keystone is now down for your cloud.
  6. Run keystone-manage db_sync on the first node. As soon as this finishes, keystone is now working again on a single node in the cluster.
  7. keystone is now upgraded on a single node. Your load balancers will be sending all traffic to this single node. This is your chance to run ensure keystone up and running, and not broken. If keystone is broken, see the Rollback after a failed upgrade section below.
  8. Once you have verified that keystone is up and running, begin the upgrade on
the other nodes. This entails updating configuration files and upgrading the code. The db_sync does not need to be run again.
  1. On the node where you stopped the database service, be sure to restart it and ensure that it properly rejoins the cluster.

Using this model, the outage window is minimized because the only time when your cluster is totally offline is between loading the newer version of keystone and running the db_sync command. Typically the outage with this method can be measured in tens of seconds especially if automation is used.

Rollback after a failed upgrade

If the upgrade fails, only a single node has been affected. This makes the recovery simpler and quicker. If issues are not discovered until the entire cluster is upgraded, a full shutdown and restore from backup will be required. That will take much longer than just fixing a single node with an old copy of the database still available. This process will be dependent on your architecture and it is highly recommended that you’ve practiced this in a development environment before trying to use it for the first time.

  1. Isolate the bad node. Shutdown keystone and the database services on the upgraded “bad” node.
  2. Bootstrap the database cluster from the node holding the old data. This may require wiping the data first on any nodes who are not holding old data.
  3. Enable keystone on the old nodes in your load balancer or if the processes were stopped, restart them.
  4. Validate that keystone is working.
  5. Downgrade the code and config files on the bad node.

This process should be doable in a matter of minutes and will minimize cloud downtime if it is required.

Upgrading without downtime

This is a high-level description of our upgrade strategy built around additional options in keystone-manage db_sync. Although it is much more complex than the upgrade process described above, it assumes that you are not willing to have downtime of your control plane during the upgrade process. With this upgrade process, end users will still be able to authenticate to receive tokens normally, and other OpenStack services will still be able to authenticate requests normally.

  1. Make a backup of your database. keystone does not support downgrading the database, so restoring from a full backup is your only option for recovery in the event of an upgrade failure.

  2. Stop the keystone processes on the first node (or really, any arbitrary node). This node will serve to orchestrate database upgrades.

  3. Upgrade your first node to the next release, but do not start any keystone processes.

  4. Update your configuration files on the first node (/etc/keystone/) with those corresponding to the latest release.

  5. (New in Newton) Run keystone-manage doctor on the first node to diagnose symptoms of common deployment issues and receive instructions for resolving them.

  6. Run keystone-manage db_sync --expand on the first node to expand the database schema to a superset of what both the previous and next release can utilize, and create triggers to facilitate the live migration process.

    At this point, new columns and tables may exist in the database, but will not all be populated in such a way that the next release will be able to function normally.

    As the previous release continues to write to the old schema, database triggers will live migrate the data to the new schema so it can be read by the next release.

  7. Run keystone-manage db_sync --migrate on the first node to forcefully perform data migrations. This process will migrate all data from the old schema to the new schema while the previous release continues to operate normally.

    When this process completes, all data will be available in both the new schema and the old schema, so both the previous release and the next release will be capable are operating normally.

  8. Update your configuration files (/etc/keystone/) on all nodes (except the first node, which you’ve already done) with those corresponding to the latest release.

  9. Upgrade all keystone nodes to the next release, and restart them one at a time. During this step, you’ll have a mix of releases operating side by side, both writing to the database.

    As the next release begins writing to the new schema, database triggers will also migrate the data to the old schema, keeping both data schemas in sync.

  10. Run keystone-manage db_sync --contract to remove the old schema and all data migration triggers.

    When this process completes, the database will no longer be able to support the previous release.