Kubernetes Ingress Controllers - What You Need to Know

Kubernetes and container technology are a match made in heaven. Kubernetes’ popularity for managing containerized applications is growing exponentially. According to Statista research, over 60% of companies stated that they adopted Kubernetes in 2022. Its success is owed to an extensive ecosystem of tools that simplify the intricacies of the approach. One such tool is Ingress Controller. As you scale your application, the complexity grows proportionately, and traffic management within the Kubernetes setup becomes a nightmare. 

In this article, we will discuss the significance of Ingress Controllers, their key features, including the ability to handle user requests coming from outside Kubernetes. We will also make a quick comparison with NodePort and LoadBalancer.

What is Kubernetes Ingress?

Kubernetes Ingress is an API object that defines how traffic from the internet, usually through HTTP and HTTPS protocols, accesses internal Kubernetes cluster services. It helps tackle networking and routing problems within the cluster. Ingress can be used to 

1. Create externally accessible URLs for Kubernetes services
2. Terminate TLS connections
3. Offer virtual hosting based on names

Typically, Ingress lists a set of routing rules within an Ingress resource, which the controller uses to execute the rules.

Decoding Ingress Controller

Consider Ingress Controller to be a foot soldier that implements Ingress-set traffic rules, acting as a reverse proxy and load balancer within a Kubernetes cluster. When Ingress resources are updated with rules, controllers change their configuration to match the updated state and execute the user request. It forms an abstraction layer to accept external traffic and distribute it across the Pods within Kubernetes.

Ingress controllers can route traffic to services based on either path or subdomain.Kubernetes Ingress controllers is used to:

• Load balance traffic from outside the Kubernetes environment to pods running inside the clusters
• Manage traffic routing between services that are a part of different clusters
• Define configurations to deploy Ingress resources
• Automate implementation fo updated load‑balancing rules monitoring pods running within a Kubernetes service

How do Ingress and Ingress Controllers work?

A user request must access the right application functionality for an application to work efficiently and without any disruptions. In the Kubernetes environment, this means that it should navigate its way through Kubernetes clusters to find the right application container. 

To address this, an Ingress controller tracks Ingress resources written in YAML or JSON, decodes it to reveal the user request, and reverse proxy can implement the configuration in the cluster. Similar to a deployment controller, the Ingress controller activates any time a user creates, changes, or deletes an Ingress.

Let us simplify the complexity of Kubernetes clusters. Clusters have Pods, which in turn contain one or more containerized applications. These computing machines are the smallest deployable units. While these Pods can communicate with each other via Services, they aren’t accessible to external networks. A Service is like an internal load balancer giving network access to Pods. 

But Kubernetes uses IP proxies to direct traffic to a particular Pod via Service. But these are ‘virtual IP addresses’ that can be used internally within the cluster and are not available for external sources. To address this situation, Kubernetes offers multiple Services types to make Pods accessible.

ClusterIP Service

ClusterIP can be used from within the cluster as this service is exposed on an internal cluster. Although it is a default setting of Kubernetes, it cannot route traffic from external users to reach the right Pods. So the real challenge is finding a way to expose the services to everyone.

NodePort Service

As the name suggests, NodePort is a Service type where every worker node has an open port. Whenever this port receives traffic, it is directed to a ClusterIP for a specific service. While this works perfectly for single-node clusters, multi-node clusters need an external load balancer to manage and send traffic across all the existing nodes. However, there are several challenge while using NodePort, including 

• Lack of means to investigate which Pods within a node have exposed ports
• Available NodePort ports are in a range of 30,000 and 32,676
• A single port only exposes a single Pod

Load Balancer

Load balancer is a service that exposes the Pods to external traffic through the cloud provider's load balancer. It uses both ClusterIP and NodePort to route traffic to a Service. However, it leads to added costs and overhead with every cluster featuring multiple services.

Advantage of Ingress Controller over Others

With Ingress, you get a smart router that brings traffic into the cluster by routing configurations through the Ingress controller. The controller is accountable for directing traffic to the right service. Ingress controller is widely accepted as it uses a single IP address for external requests, which is then connected to the internal IP for traffic to traverse between services. This means the team is not flooded with several IPs.

While NodePort is simple, you must remember the IPs of individual worker nodes; Load Balancer can connect external requests to the right port. But the load balancer is an expensive option. 

Verdict - Ingress is preferred over NodePort and LoadBalancer because it allows you to bind routing rules in a single resource to give access to multiple services. 

Features of Ingress Controller

1. Facilitates dynamic reconfiguration by constantly updating the load balancer configuration to reflect changes made to Ingress resources.
2. Doubles up as a Web Application Firewall (WAF) by offering resistance against OWASP Top 10 and other vulnerabilities to protect your apps and APIs.
3. Implement robust authorization & authentication standards via single sign-on solutions.

ChatGPT for Kubernetes and more

Kubernetes Ingress is a powerful method that bridges external requests with Kubernetes services. But it holds no ground to do so without an Ingress controller. The controller simplifies sending traffic from outside the Kubernetes ecosystem to within clusters through a secure path. Ingress controllers can automate traffic management without any extra costs and effort. Something that allows you to do the same across the Kubernetes practice is Kubiya, an AI-based assistant. To draw a parallel, Kubiya.AI is like ChatGPT for managing your operational processes and cloud infrastructure. And the best part - you can start for free today in our public sandbox and experience it yourself.