Consider the special circumstances of a patched Controller.

For more information on patch process, see Patch Upgrade Process.

  • The patch process requires logging into the Avi Load Balancer CLI as the admin user.

  • Being able to log in as an admin user implies the factory-default admin password has been changed, as explained in the Strong Default Admin Password section.

  • As mentioned, follower nodes are expected to have no configuration, and no changes to the Avi Load Balancer login credentials. If follower nodes do have credentials, a message of the following form is displayed if one attempts to cluster them:

    Cluster configuration failed. Unable to add node 1.2.3.4: Login with default credentials failed, clean reboot the node and retry.

    Therefore, before joining two patched Controller-followers to a patched Controller-leader, run reboot clean commands on each follower.

  • A Controller which has had its admin password changed has a configuration.

Transition Process

  • Trust is established between the leader and new followers over HTTPS.

  • The leader exports cluster state information to each follower over SSH.

  • Each node locally applies the cluster state information, and restarts services.

  • Existing Avi Load Balancer SEs, originally connected to only the leader node, detect the cluster membership changes and connect to all the Avi Load Balancer Controller nodes in the cluster.

Note:

During this transition, the REST API is not available. Generally, the transition takes four to ten minutes.

Transition Status

The progress of transition to a 3-node cluster is indicated by the following status messages:

  • Configuration is in progress: During this phase, Avi Load Balancer verifies the configuration and verifies the state information on each of the new nodes. Only nodes with no state can be added to the cluster. Avi Load Balancer also updates the cluster database, and launches a configuration script on each of the nodes.

  • Inaccessible: Avi Load Balancer Controller processes are restarted.

  • Restoring: Avi Load Balancer configuration is synchronized across all nodes.

  • Waiting for Service Engines to connect: Avi Load Balancer waits for any known SEs that have not yet connected to and registered with any of the Avi Load Balancer Controller nodes.

  • Ready

If dismantling a cluster (returning to only a single Avi Load Balancer Controller node), the status messages are the same. However, during the Configuration is in progress phase, the state information on the followers is ignored.