Service
Each pod in the Kubernetes cluster is assigned an internal IP address. Since pods are created and deleted and their IP addresses change, it makes no sense to use IP addresses for pods directly. Use services to get permanent access to pods and stop using their internal IP addresses.
A service is a Kubernetes API object that provides access to an application running as a set of pods in a Kubernetes cluster.
If you use a service, you get a permanent IP address that exists throughout the service lifecycle, even if pods change their IP addresses. It also provides load balancing. Clients send requests to a single IP address, and their requests are balanced between the pods belonging to the service.
The set of pods belonging to the service is defined by a selector. The selector is configured by the user when creating the pod and allows filtering the list of resources based on labels, i.e., key-value pairs attached to the resource. The pod belongs to the service if it has all the Kubernetes labels specified in the selector.
Depending on your task, you can use different types of services.
Service types
You can use various types of services in your Kubernetes clusters, including:
ClusterIP- You can access the service only within the Kubernetes cluster network using an internal IP address.
- It requires no additional cloud resources.
NodePort:ClusterIPtype extension.- It provides access to the service via internal or public Kubernetes cluster node IP addresses.
- It requires no additional cloud resources.
LoadBalancer:NodePorttype extension.- It provides access to the service via a cloud network load balancer you create.
- It requires additional cloud resources: a network load balancer.
To publish your application, use a LoadBalancer service based on a network load balancer with a public or internal IP address.
If DDoS protection is required, reserve a public IP address with protection enabled and specify it using the loadBalancerIP option.
Learn more about service types in this Kubernetes guide.