Services

Services in Kubernetes are abstraction layers for routing traffic to a logical set of pods. With Services, we don't need to trace the IP address of each pod. Services usually use the label selector to select the pods that they need to route to while, in some cases, Services are created without a selector on purpose. The Service abstraction is powerful. It enables decoupling and makes communication between micro-services possible. Currently, Kubernetes Services support TCP, UDP, and SCTP.

Services don't care about how we create the pod. Just like ReplicaSet, it only cares that the pods match its label selectors, so the pods could belong to different ReplicaSets:

In the preceding diagram, all of the pods match the service selector, project=chapter3, service=web, so the Service will be responsible for distributing the traffic into all of the pods without explicit assignment.

There are four types of Services: ClusterIP, NodePort, LoadBalancer, and ExternalName: