As per the official documentation :
In Kubernetes, a Service is a method for exposing a network application that is running as one or more Pods in your cluster. It is an abstraction to help you expose groups of Pods over a network. Each Service object defines a logical set of endpoints (usually these endpoints are Pods) along with a policy about how to make those pods accessible.
The SERVICE object provides a stable IP address for the CLIENT container on NODE X to send a request to any one of the API containers.
Kubernetes uses labels on the pods to select the pods that are associated with a service. To include a pod in a service, the pod labels must include each of the selector fields of the service.
ClusterIP :
It is the default service type, You can only access this service while inside the cluster. NO external access ( unless you are using a proxy ).
apiVersion: v1
kind: Service
metadata:
name: my-service
spec:
type: ClusterIP
selector:
tier: backend
ports:
- protocol: TCP
port: 80
targetPort: 8080
selector is used to select the pods who has a label "tier=backend"
Service listens on port 80/TCP and forwards the requests to the back-end pod on port 8080.
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NodePort:
With this method, Kubernetes exposes a service on a port on the node IP address. The port is exposed on all cluster nodes, and each node redirects traffic to the endpoints (pods) of the service.
apiVersion: v1
kind: Service
metadata:
name: my-service
spec:
type: NodePort
selector:
tier: backend
ports:
- port: 80
targetPort: 80
nodePort: 30007
Port --> Port of the service
targetPort --> Port open on the Pod
NodePort --> port open on the node ( Range 30000-32767)
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LoadBalancer :
On cloud providers which support external load balancers, setting the type field to LoadBalancer provisions a load balancer for your Service:
apiVersion: v1
kind: Service
metadata:
name: my-service
spec:
selector:
tier: backend
ports:
- protocol: TCP
port: 80
targetPort: 8080
clusterIP: 10.0.171.239
type: LoadBalancer
status:
loadBalancer:
ingress:
- ip: 192.0.2.127
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Ingress: not a service type but a rule to chart external access to services
Ingress exposes HTTP and HTTPS routes from outside the cluster to services within the cluster. Traffic routing is controlled by rules defined on the Ingress resource.
An Ingress may be configured to give Services externally-reachable URLs, load balance traffic, terminate SSL / TLS, and offer name-based virtual hosting.
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: minimal-ingress
annotations:
nginx.ingress.kubernetes.io/rewrite-target: /
spec:
ingressClassName: nginx-example
rules:
- http:
paths:
- path: /testpath
pathType: Prefix
backend:
service:
name: my-service
port:
number: 80
This Ingress resource configures the Nginx Ingress Controller (nginx.ingress.kubernetes.io) to handle traffic with the nginx-example class. It routes HTTP requests with a path starting with /testpath to the "my-service" service on port 80 within the Kubernetes cluster.
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Refer : https://kubernetes.io/docs/concepts/services-networking/
