Kubernetes - Services

We’ve spun up pods and connected to them individually, but that’s frankly not super useful if we want to distribute real traffic across those pods. That’s where services come in.
Services provide a stable endpoint for pods. They are an abstraction used to provide a stable endpoint and load balance traffic across a group of Pods. By “stable endpoint”, I just mean that the service will always be available at a given URL, even if the pod is destroyed and recreated.

Service Type

There are four types of services in Kubernetes:
- ClusterIP
- NodePort
- LoadBalancer
- ExternalName
ClusterIP: Exposes the service on a cluster-internal IP. Choosing this value makes the service only reachable from within the cluster. This is the default ServiceType.
NodePort: Exposes the service on each Node’s IP at a static port (the NodePort). A ClusterIP service, to which the NodePort service will route, is automatically created. You’ll be able to contact the NodePort service, from outside the cluster, by requesting NodeIP:NodePort.
LoadBalancer: Exposes the service externally using a cloud provider’s load balancer. NodePort and ClusterIP services, to which the external load balancer will route, are automatically created.
ExternalName: Maps the service to the contents of the externalName field (e.g. foo.bar.example.com), by returning a CNAME record with its value. No proxying of any kind is set up.

Ingress is an API object that manages external access to services in a cluster, typically HTTP. Ingress may provide load balancing, SSL termination and name-based virtual hosting.
Ingress is not a service type, but it acts as the entry point for your cluster. It lets you consolidate your routing rules into a single resource, rather than having to manage each service’s route individually.
Ingress is a layer 7 (HTTP) load balancer, whereas services are layer 4 (TCP/UDP) load balancers.
Ingress is a collection of rules that allow inbound connections to reach the cluster services. It can be configured to give services externally-reachable URLs, load balance traffic, terminate SSL, offer name-based virtual hosting, and more.