Kubernetes Service

Service is the core object in Kubernetes. In Chapter 3 you learned what Kubernetes service is and how to create a service object with a YAML file. Functionally, a service is running as a Layer 4 (transport layer) load balancer that is sitting between clients and servers. Clients can be anything requesting a service. The server in our context is the backend pods responding to the request. The client only sees the frontend - a service IP and service port exposed by the service, and it does not (and does not need to) care about which backend pods (and what pod IP) actually responds to the service request. Inside of the cluster, that service IP, also called cluster IP, is a kind of virtual IP (VIP).

In the Contrail environment it is implemented through floating IP.

Note

This design model is very powerful and efficient in the sense that it covers the fragility of the possible single point failure that may be caused by failure of any individual pod providing the service, therefore making a service much more robust from client’s perspective.

In the Contrail Kubernetes integrated environment, all three types of services are supported:

clusterIP
nodePort
loadbalancer

Now let’s see how the service is implemented in Contrail.