In Kubernetes, a Service is an internal load balancer which identifies a set of pods and can proxy traffic to them. This set of pods is determined by a label selector.

A service is a stable way of accessing a set of pods, which are ephemeral.

When a service is created, it is granted a ClusterIP, which is an IP address internal to the Kubernetes cluster. Other pods can use this ClusterIP to access the service.

Here is an example service definition:

apiVersion: v1
kind: Service
  name: my-service
    name: my-app
  - port: 8080
    protocol: TCP
    targetPort: 8080

This definition tells Kubernetes that all pods with the label “my-app” are associated with this service. Any traffic to the service should be distributed among these pods.

The port parameter contains what port the service listens on, and the targetPort parameter contains the port to which the service forwards connections.

Creating Services


On the command line, services can be created with the command oc create. Assuming our YAML file from above is in the file my-service.yaml, you can create the service with

$ oc create -f my-service.yaml

Then, you can run oc describe service my-service to see some information about it.

$ oc describe service my-service
Name:                   my-service
Labels:                 <none>
Selector:               name=my-app
Type:                   ClusterIP
Port:                   <unnamed>       8080/TCP
Endpoints:    ,,
Session Affinity:       None
No events.

In this example, looking at Endpoints, we have 3 pods running with the my-app selector. This means that from inside the cluster if an application accesses the ClusterIP on port 8080 the traffic will be directed to one of the three pods.

Accessing Services from Outside the Cluster

A service of type ClusterIP will only ever be accessible from inside the cluster. If you need access to your service from outside of the cluster there are a few different options.


In general, using FQDNs to access a service is more convenient. If your service communicates over HTTP or HTTPS, you can set up a Routes to achieve this. If your service uses another protocol, you can use NodePorts.


NodePort is a type of Service that reserves a port across the cluster that can route traffic to your pods. This is more flexible than a Route and can handle any TCP or UDP traffic.