Kubernetes Ingress Concepts
External
Internal
Overview
An Ingress is a mechanism that operates at the application layer of the network stack (HTTP) and brings layer 7 features such as host and path-based routing and cookie-based session affinity to services. Ingress cooperates with services to distribute load to pods. It exposes multiple services through a single IP address, and its implementation differs fundamentally from the implementation of ClusterIP, NodePort and LoadBalancer services. The reasons to use an Ingress include:
- One Ingress can serve multiple services, behind a single public IP address, while each LoadBalancer requires its own native load balancer, each of them requiring their own public IP address.
- Host, paths and cookies can be used to route the request.
The Ingress mechanism consists of an Ingress controller and an Ingress resource.
Ingress Controller
The ingress controller is the process - most likely running as a pod or pods inside the Kubernetes cluster itself - that accepts the HTTP connections, distributes traffic, terminates SSL connections, etc. Some Kubernetes distributions provide an ingress controller as an "add-on". For example, minikube provides to "minikube addons enable ingress" command. If the ingress controller is not provided as add-on, it can be installed. There is a default "ingress-nginx" ingress controller that can be installed in any Kubernetes instance. More details:
Ingress API Resource
An Ingress is the Kubernetes API resource that manages access to level 4 services in a cluster.