Creating a Cluster: Discussing the Specifications

We are finally ready to create a cluster. But before we do that, we’ll spend some time discussing the requirements we might have. After all, not all clusters are created equal, and the choices we are about to make might severely impact our ability to accomplish the goals we might have.

Primary nodes

The first question we might ask ourselves is whether we want high availability. It would be strange if anyone answers no. Who doesn’t want to have a cluster that is (almost) always available? Instead, we’ll ask ourselves what things might bring our cluster down.

When a node is destroyed, Kubernetes will reschedule all the applications that were running inside it to healthy nodes. All we have to do is to make sure that, later on, a new server is created and joined to the cluster so that its capacity is back to the desired values. We’ll discuss later how new nodes are created as a reaction to failures of a server. For now, we’ll assume that will happen somehow.

Still, there is a catch. Given that new nodes need to join the cluster, if the primary server fails, there is no cluster to join. All is lost. The most important part is where the primary servers are. They host the critical components without which Kubernetes cannot operate.

So, we need more than one primary node. How about two? If one fails, we still have the other one. ...