A service can be defined as a logical set of pods. It can be defined as an abstraction on the top of the pod which provides a single IP address and DNS name by which pods can be accessed. With Service, it is very easy to manage load balancing configuration. It helps pods to scale very easily.
A service is a REST object in Kubernetes whose definition can be posted to Kubernetes apiServer on the Kubernetes master to create a new instance.
Service without Selector
apiVersion: v1 kind: Service metadata: name: Tutorial_point_service spec: ports: - port: 8080 targetPort: 31999
The above configuration will create a service with the name Tutorial_point_service.
Service Config File with Selector
apiVersion: v1
kind: Service
metadata:
name: Tutorial_point_service
spec:
selector:
application: "My Application" -------------------> (Selector)
ports:
- port: 8080
targetPort: 31999
In this example, we have a selector; so in order to transfer traffic, we need to create an endpoint manually.
apiVersion: v1
kind: Endpoints
metadata:
name: Tutorial_point_service
subnets:
address:
"ip": "192.168.168.40" -------------------> (Selector)
ports:
- port: 8080
In the above code, we have created an endpoint which will route the traffic to the endpoint defined as “192.168.168.40:8080”.
Multi-Port Service Creation
apiVersion: v1
kind: Service
metadata:
name: Tutorial_point_service
spec:
selector:
application: “My Application” -------------------> (Selector)
ClusterIP: 10.3.0.12
ports:
-name: http
protocol: TCP
port: 80
targetPort: 31999
-name:https
Protocol: TCP
Port: 443
targetPort: 31998
Types of Services
ClusterIP − This helps in restricting the service within the cluster. It exposes the service within the defined Kubernetes cluster.
spec:
type: NodePort
ports:
- port: 8080
nodePort: 31999
name: NodeportService
NodePort − It will expose the service on a static port on the deployed node. A ClusterIP service, to which NodePort service will route, is automatically created. The service can be accessed from outside the cluster using the NodeIP:nodePort.
spec:
ports:
- port: 8080
nodePort: 31999
name: NodeportService
clusterIP: 10.20.30.40
Load Balancer − It uses cloud providers’ load balancer. NodePort and ClusterIP services are created automatically to which the external load balancer will route.
A full service yaml file with service type as Node Port. Try to create one yourself.
apiVersion: v1
kind: Service
metadata:
name: appname
labels:
k8s-app: appname
spec:
type: NodePort
ports:
- port: 8080
nodePort: 31999
name: omninginx
selector:
k8s-app: appname
component: nginx
env: env_name