In any Kubernetes cluster, applications must be able to connect with the outside world to provide end-users with access to the application. Kubernetes Ingress is one option available—let’s take a look.

(This article is part of our Kubernetes Guide. Use the right-hand menu to navigate.)

What is Kubernetes Ingress?

Kubernetes Ingress is an API object that provides routing rules to manage access to the services within a Kubernetes cluster. This typically uses HTTPS and HTTP protocols to facilitate the routing.

Ingress is the ideal choice for a production environment. Users can expose services within the Kubernetes cluster without having to create multiple load balancers or manually exposing services.

Moreover, K8s Ingress offers a single entry point for the cluster, allowing administrators to manage the applications easily and diagnose any routing issues. This decreases the attack surface of the cluster, automatically increasing the overall security.

Some use cases of Kubernetes Ingress include:

• Providing externally reachable URLs for services
• Load balancing traffic
• Offering name-based virtual hosting
• Terminating SSL (secure sockets layer) or TLS (transport layer security)

Kubernetes Ingress supports multiple protocols, authentication, content-based routing, etc., and allows users to manage and configure them in Kubernetes clusters easily.

Kubernetes Ingress consists of two core components:

• Ingress API object. The API object indicates the services that need to be exposed outside the cluster. It consists of the routing rules.
• Ingress Controller. Ingress Controller is the actual implementation of Ingress. It is usually a load balancer that routes traffic from the API to the desired services within the Kubernetes cluster.

What is an Ingress controller?

The actual implementation of Kubernetes Ingress, the Ingress controller is responsible for the traffic routing from external sources to the appropriate services in the Kubernetes cluster. Ingress controllers support routing through both the transport layer (OSI – Layer 4) and the application layer (OSI – Layer 7) in the OSI model.

The application layer routing is preferred over simple transport layer routing because it offers greater control, such as load balancing external traffic based on requests. The Ingress controllers are neither automatically started with a Kubernetes cluster nor a part of the default “kube-controller-manager” binary.

Kubernetes offers built-in support for AWS, GCE, and nginx ingress controllers and also supports integration with third-party ingress controllers. The choice of the Ingress controller depends on:

• Your application requirements
• The host environment

Simply put, the Ingress controller is an application that runs within the Kubernetes cluster and provisions a load balancer according to the requirements of Ingress. (The load balancer can be a software load balancer, external hardware load balancer, or cloud load balancer, each type requiring different controller implementations.)