This section explains various upgrade scenarios in an Avi Load Balancer deployment in which GSLB has been configured.

Some circumstances mandate an immediate cessation of service, while others permit a graceful upgrade without interruption of service. The Avi Load Balancer GSLB implementation supports graceful upgrades, even when challenged by actions such as:

  1. A new version of Avi Load Balancer needs to be installed on active and passive GSLB sites.

  2. A site-wide change must be made.

  3. An application server (or servers) must be replaced or its configuration changed.

  4. A new version of an executable of the global application needs to be installed on all site servers currently running it.

Avi Load Balancer Upgrades

Note:

To avoid service disruption due to site upgrades, it is recommended that the DNS virtual service must be scaled out to at least two SEs within the SE group.

For more information on the Avi Load Balancer upgrade process, see Upgrade Guide in the VMware Avi Load Balancer Administration Guide.

For more information on pre-upgrade, see Pre-upgrade Steps.

Error Scenarios

Follower Upgrade Failure

If the upgrade of a follower site fails, it will end in a GSLB disruption. The site will roll back to the previous version and come up. On the GSLB leader, disable maintenance mode. After determining the reason for failure and addressing it, resume the upgrade process.

Leader Upgrade Failure

On the leader, disable maintenance mode. Determine the reason and address it. In the meantime, no new features can be activated.

Mixing Avi Load Balancer Versions

Avi Load Balancer recommends that all sites participating in GSLB run at the same version and maintenance release.

During upgrade cycles, it might not be possible or desirable to upgrade all sites to the same software version in a single maintenance window. In this situation, it is supported to mix sites running different versions of Avi Load Balancer for some time with the following caveats:

  1. The GSLB leader site must be the last to be upgraded. There is no explicit support for the leader site to be running a later software version or maintenance release than any of the GSLB follower sites.

  2. GSLB configuration changes can be carried out on the leader during the period when the sites are running mixed software versions, with the caveat that new GSLB features in the later software version cannot be turned on until all sites have been upgraded.