What is an ingress controller and why is it important to Kubernetes?

Moving production workloads onto Kubernetes presents new difficulties and complexities for many businesses in managing application traffic. A bridge between Kubernetes services and external ones is provided by an Ingress controller, which abstracts away the difficulty of Kubernetes application traffic routing.

Kubernetes Ingress is an API object that manages external access to the services in a Kubernetes cluster, typically HTTP. It allows for routing incoming traffic to different services based on the host or path of the HTTP request, and can also provide additional features such as authentication and SSL termination. Ingress is implemented as a collection of rules that define how requests should be routed to the underlying services. These rules are defined using Ingress resources, which are created and managed using the Kubernetes API. Ingress controllers, such as NGINX or HAProxy, are used to implement the actual routing of traffic based on the rules defined in the Ingress resources.

Why Were Ingress Controllers Created?

In Kubernetes, pods are the smallest unit of application computing and stand for a compact, remarkably coherent unit of an application. As a result, the set of Pod container instances that are active at any given time may change later.

This raises the following issue: How do the frontends determine and keep track of which IP address to connect to when container instances come and go if one set of Pods (imagine a frontend Pod) has to communicate with another set of Pods (picture a backend Pod)?

A “Service” abstraction, which is the external interface to a logical group of Pods, was developed by Kubernetes to address this issue. Kubernetes employs IP proxy mechanisms within a cluster to make sure that traffic meant for a Service is directed to one of the relevant Pod container instances. External services must use a separate method to connect to the Service endpoint since this uses a “virtual IP address” that is internal to the cluster. This issue is addressed with Kubernetes Ingress.

Ingress controllers are important to Kubernetes because they provide a way to control and configure external access to the services in a cluster. Without an ingress controller, external traffic would need to be directed to individual services using separate load balancers or other external networking configurations. With an ingress controller, all external traffic can be routed to the ingress controller and then directed to the appropriate service based on the ingress rules. 

Ingress controllers also provide additional functionality such as authentication, rate limiting, and service-to-service authorization, which can be useful in securing and managing external access to services in a cluster. Additionally, Ingress controllers are built on top of load balancers and proxies which can provide better performance, scalability, and other features like SSL offloading, traffic shaping, etc.

Emissary Ingress Controller 

There are several popular ingress controllers available, such as Nginx, Traefik, and HAProxy. These controllers can be deployed as part of a Kubernetes cluster and configured using Kubernetes resources such as ingress, service, and config maps. 

Emissary is a new entrant in the ingress controller space, which runs as a Kubernetes operator and provides simple and fast ingress on Kubernetes clusters using Envoy. Envoy is a high-performance open-source edge and service proxy that is often used as an ingress controller in Kubernetes. The Emissary operator provides a simplified configuration, easy updates, and centralized management for Envoy’s ingress function for Kubernetes.

In a Kubernetes cluster, ingress controllers play an important role in managing external access to services. They provide a way to control and configure external access to the services in a cluster, making it easier to secure and manage external access to the services. With the rise of cloud-native architectures and the increasing adoption of Kubernetes, ingress controllers are becoming an essential component of modern infrastructure. Emissary is an open-source ingress controller built on top of Envoy proxy. It provides a simplified configuration for ingress traffic management and is a good option to consider while managing ingress traffic in Kubernetes clusters.

To conclude

An ingress controller is a vital component for managing external access to services in a Kubernetes cluster, it acts as a reverse proxy to route incoming traffic to the appropriate service, providing centralized management, improved security, better performance, scalability, flexibility, ease of use and can also act as an API Gateway. There are various ingress controllers available like Nginx, Traefik, HAProxy, and Emissary, each with its own set of features and configuration options, making it easy to select the right one for the specific use case. Overall, ingress controllers are essential for managing the external traffic in a k8s cluster and provide security, scalability, and ease of use benefits. 

To know more about ingress controllers and about the Emissary ingress controller, watch the interview here:

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