The moment we start to work with applications consisting of more than one application service, we need service discovery. The following diagram illustrates this problem:
In the preceding diagram, we have a Web API service that needs access to three other services: payments, shipping, and ordering. The Web API should never have to care about how and where to find those three services. In the API code, we just want to use the name of the service we want to reach and its port number. A sample would be the following URL http://payments:3000, which is used to access an instance of the payments service.
In Kubernetes, the payments application service is represented by a ReplicaSet of pods. Due to the nature of highly distributed systems, we cannot assume that pods have stable endpoints. A pod can...