How to create Kubernetes Service?

Creating a Kubernetes Service

In Kubernetes, a Service is an abstraction that defines a logical set of Pods and a policy by which to access them. Services provide a stable endpoint for accessing one or more Pods, even as the underlying Pods are created, destroyed, or scaled up and down.

To create a Kubernetes Service, you can use the kubectl create service command or define a Service manifest in a YAML file and apply it to your Kubernetes cluster.

Creating a Service using `kubectl create service`

The kubectl create service command allows you to quickly create a Service with a few basic parameters. Here's an example:

kubectl create service clusterip my-service --tcp=8080:80

This command creates a ClusterIP Service named my-service that exposes port 80 on the Pods and forwards it to port 8080 on the Service.

The clusterip type is the default Service type, which provides a stable IP address and DNS name for Pods within the cluster to access the Service.

Creating a Service using a YAML manifest

Alternatively, you can define a Service in a YAML file and apply it to your Kubernetes cluster. Here's an example Service manifest:

apiVersion: v1
kind: Service
metadata:
  name: my-service
spec:
  selector:
    app: my-app
  ports:
  - port: 80
    targetPort: 8080
  type: ClusterIP

In this example, the Service is named my-service and it selects Pods with the label app: my-app. The Service exposes port 80 and forwards it to port 8080 on the Pods.

The type: ClusterIP field specifies that this is a ClusterIP Service, which provides a stable IP address and DNS name for Pods within the cluster to access the Service.

You can apply this YAML manifest to your Kubernetes cluster using the kubectl apply command:

kubectl apply -f my-service.yaml

Service Types

Kubernetes supports different types of Services, each with its own use case:

graph TD A[Service Types] A --> B[ClusterIP] A --> C[NodePort] A --> D[LoadBalancer] A --> E[ExternalName] B --> F[Default Service type] B --> G[Exposes a Service on a cluster-internal IP] C --> H[Exposes a Service on each Node's IP at a static port] D --> I[Exposes a Service externally using a cloud provider's load balancer] E --> J[Maps the Service to a DNS name, not a typical IP:port]

ClusterIP: The default Service type, which exposes the Service on a cluster-internal IP address. This type of Service is only accessible from within the cluster.
NodePort: Exposes the Service on each Node's IP at a static port. You can then access the Service by requesting <NodeIP>:<NodePort>.
LoadBalancer: Exposes the Service externally using a cloud provider's load balancer. This is the recommended way to expose a Service to the internet.
ExternalName: Maps the Service to a DNS name, not a typical IP:port combination.

The choice of Service type depends on your specific use case and the requirements of your application.

Conclusion

In summary, creating a Kubernetes Service involves defining the Service's properties, such as the selector, ports, and type. You can create a Service using either the kubectl create service command or by defining a Service manifest in a YAML file and applying it to your cluster. Understanding the different Service types and their use cases is crucial for designing and deploying effective Kubernetes applications.