Services

The final basic tool that Kubernetes gives us to manage our applications is the service. Services give us a convenient way of accessing our services within our cluster, something often referred to as service discovery.

In practice, a service allows us to define a label selector to refer to a group of pods and then map that to something that our application can consume, without having to be modified to query the Kubernetes API to gather this information. Typically, a service will provide a stable IP address or DNS name that can be used to access the underlying pods that it refers to in a round robin fashion.

By using a service, our applications don't need to know that they are running on Kubernetes-we just need to configure them correctly with the DNS name or IP address of a service that they depend on.

A service provides a way for other applications in the cluster to discover pods that match a particular label selector. It does this by providing a stable IP address and, optionally, a DNS name. This setup is shown in the following diagram: