Rolling upgrade - cluster

Prerequisite

A cluster configuration should include at least two nodes with a load balancer positioned in front. The load balancer must have the capability to be configured to redirect traffic selectively to one node at a time during the upgrade process.

Danger

Usage of a test environment is always a best practice. Even though it may be hard maintaining replicas of production setup it is a strong recommendation.

Steps of execution

1. Configure load balancer to redirect traffic to one node only.
2. Split the cluster - On all other nodes, configure them as stand alone.
3. Configure load balancer to redirect traffic to one of the node configured to be stand alone from previous stage.
4. On the remaining node, configure to be stand alone.
5. Execute upgrade on all nodes not receiving traffic.
6. Verify functionality on upgraded nodes.
7. If using more than two node, create cluster including all nodes but the one receiving traffic. Include the remaining node, still working stand alone, in configuration
8. Redirect traffic the upgraded node(s).
9. Upgrade remaining node and include into cluster.
10. Configure load balancer to include last node in worker list.