backing the Service. Long story short, each Pod gets a DNS entry where clients can directly reach out to it in a predictable way. For example, if our random-generator Service belongs to the default  namespace, we can reach our rg-0  Pod through its fully qualified domain name: rg-0.random-generator.default.svc.clus ter.local , where the Pod’s name is prepended to the Service name. This mapping allows other members of the clustered application or other clients to reach specific Pods if they wish to. 

We can also perform DNS lookup for SRV records (e.g., through dig SRV random- generator.default.svc.cluster.local ) and discover all running Pods registered with the StatefulSet’s governing Service. This mechanism allows dynamic cluster member discovery if any client application needs to do so. The association between the headless Service and the StatefulSet is not only based on the selectors, but the StatefulSet should also link back to the Service by its name as serviceName: "random-generator" . 

Having dedicated storage defined through volumeClaimTemplates  is not mandatory, but linking to a Service through serviceName  field is. The governing Service must exist before the StatefulSet is created and is responsible for the network identity of the set. You can always create other types of Services additionally that load balance across your stateful Pods if that is what you want. 

As shown in Figure 11-1, StatefulSets offer a set of building blocks and guaranteed behavior needed for managing stateful applications in a distributed environment. It is up to you to choose and use them in a way that is meaningful for your stateful use case. 

