This topic describes what you can expect regarding the availability of
cf push during upgrades of VMware Tanzu Application Service for VMs (TAS for VMs).
cf push during TAS for VMs upgrades varies from release to release. There are various considerations, such as Cloud Controller database (CCDB) migrations or the number of VMs in use, that can impact
cf push availability. However,
cf push is mostly available for the duration of an upgrade.
Having a single VM in use, such as a WebDAV, a HAProxy, a Gorouter, a UAA, or a Cloud Controller, impacts whether
cf push is unavailable during an upgrade.
If you have scaled out your app to achieve high availability and are not using WebDAV,
cf push should be available for the entire duration of the upgrade. However, upgrades to certain versions of TAS for VMs sometimes require a CCDB schema or data migration, which may cause
cf push to be unavailable while Cloud Controllers are rolling during the upgrade.
The Cloud Controller API is taken down during the
pre-backup-lock stage of a BBR backup and put back up again during the
post-backup-unlock stage. As a result,
cf push becomes unavailable during that time. However, the backup that takes place between those stages is very short, no longer than a few minutes. The bulk of the BBR backup operation happens after the
post-backup-unlock stage, so the Cloud Controller API and
cf push are available for most of the duration of a BBR backup.
The Uptimer tool can help you measure
cf push availability during an upgrade. For more information, see the Uptimer repository on GitHub.