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Perform a Rolling Upgrade

This guide walks through upgrading every node in a running Ella Core high-availability cluster, one at a time, without taking the cluster offline. For background on mixed-version clusters, draining, and schema coordination, see High Availability.

Prerequisites

  • A running cluster deployed via Deploy a High Availability Cluster.
  • Admin credentials for the Ella Core UI, or an admin API token.
  • The target Ella Core version available on the snap channel you track.

Upgrade one node

Repeat these steps for each node, upgrading the leader last.

  1. Identify the leader on the Cluster page of any healthy node.
  2. Pick the next node to upgrade — a follower, unless this is the last pass.
  3. Click Drain next to that node. Wait until its Drain State is drained.

  4. On that host, refresh the snap:

    sudo snap refresh ella-core

  5. On the Cluster page, wait for the node to return to Healthy.

  6. Click Resume next to the node. Wait for Drain State to clear back to active.
  7. Move to the next node.

Verify the upgrade

After every node has been refreshed, open the Cluster page and confirm:

  • Every node's Version column shows the target release.
  • The mixed-version warning banner is gone.
  • Every node is Healthy and its Drain State is active.

Note

All steps in this guide can also be performed via the REST API. See the Cluster API reference for details.