What Happens During PAS Upgrades
This topic explains what happens to Pivotal Application Service (PAS) components and apps during a PAS upgrade.
During a PAS upgrade, BOSH drains all Diego cell VMs that host app instances. BOSH manages this process by upgrading a batch of cells one at a time.
When BOSH triggers an upgrade, each upgrading Diego cell enters evacuation mode. In evacuation mode, BOSH stops Diego cells and then schedules replacements for its app instances.
For more information, see Diego Cell Upgrade Process.
cf push is mostly available for the duration of a PAS upgrade. However,
cf push can become unavailable when a single VM is in use or during BOSH Backup and Restore (BBR).
For more information, see cf push Availability During Pivotal Application Service Upgrades.
During a PAS upgrade, components upgrade in a specific order. In a single-component environment, upgrading can cause the deployment to experience downtime and other limitations.
For more information, see Upgrade Order and Limitations.
For sample performance measurements of an upgrading Cloud Foundry installation, see Upgrade Load Example: Pivotal Web Services.