Services

A Service defines a policy to access a logical set of Pods using a reliable endpoint. Users and other programs can access pods running on your cluster seamlessly. Therefore allowing a loose coupling between dependent Pods.

When a request arrives the endpoint, the kube-proxy pod of the node forwards the request to the Pods that match the service LabelSelector.

Services can be exposed in different ways by specifying a type in the ServiceSpec:

• ClusterIP (default): Exposes the Service on an internal IP in the cluster. This type makes the Service only reachable from within the cluster.

• NodePort: Exposes the Service on the same port of each selected Node in the cluster using NAT to the outside.

• LoadBalancer: Creates an external load balancer in the current cloud and assigns a fixed, external IP to the Service.

  To create an internal ELB of AWs add to the annotations:

  annotations:
    service.beta.kubernetes.io/aws-load-balancer-internal: 0.0.0.0/0
  

• ExternalName: Exposes the Service using an arbitrary name by returning a CNAME record with the name. No proxy is used.

If no RBAC or NetworkPolicies are applied, you can call a service of another namespace with the following nomenclature.

curl {{ service_name}}.{{ service_namespace }}.svc.cluster.local