What Is Kubernetes Ingress? How It Works, Architecture, and a Detailed Deployment Guide

In a Kubernetes environment, exposing applications to the outside world is always one of the most important steps. This is why Kubernetes Ingress has become an optimal solution for managing traffic entering a cluster in a flexible, secure, and cost-effective manner. In the following article, Viettel IDC will help you gain a deeper understanding of Ingress, how it works, its architecture, and the value it brings to modern application deployments.

What Is Kubernetes Ingress?

Kubernetes Ingress is an object that allows you to manage how external users access services inside a Kubernetes cluster. Instead of opening multiple ports, creating multiple LoadBalancers, or deploying reverse proxies manually, you only need to define routing rules in an Ingress, while the Ingress Controller handles routing traffic to the appropriate services.

Ingress acts as a centralized gateway for receiving HTTP/HTTPS requests and distributing them to backend services based on domains or paths. This makes system management much simpler, especially when an application consists of multiple microservices. With Ingress, you only need a single entry point for the entire application while maintaining centralized control over traffic.

Why Is Kubernetes Ingress Needed?

Before Ingress, most Kubernetes applications used NodePort or LoadBalancer to expose services publicly. However, these approaches are not efficient in complex environments or when multiple services are involved. NodePort requires ports to be opened on every node, making them difficult to manage and limiting the available port range. Although LoadBalancer is convenient, it can be very expensive because each service requires a separate load balancer.

Ingress addresses these issues by creating a centralized routing layer. You can use a single LoadBalancer externally, after which all traffic is directed to the Ingress Controller. The controller then analyzes the domain, path, and configured rules to route traffic to the desired service. This reduces costs, increases flexibility, and makes the system easier to scale.

Kubernetes Ingress Architecture

To understand how Ingress works, you first need to understand its architectural components. Each component plays an important role in ensuring that traffic from outside the cluster reaches the correct internal service.

Ingress Resource

An Ingress Resource is a YAML-based object containing routing configuration, including domains, paths, TLS, and routing rules. This is the component that users create within Kubernetes. The Ingress Resource only defines the routing logic, while its actual implementation depends on the Ingress Controller. You can define multiple rules within a single Ingress or split them across multiple Ingress resources for individual applications, depending on how your system is organized.

Ingress Controller

The Ingress Controller is the component responsible for processing traffic in Kubernetes. It reads the rules defined in the Ingress Resource and translates them into configurations for reverse proxies such as NGINX, HAProxy, Traefik, or Envoy. The Ingress Controller is also responsible for monitoring changes within the cluster, updating routing configurations, managing SSL, and implementing advanced features. Without a controller, an Ingress Resource exists only as a configuration object and cannot actually handle traffic.

Backend Service

The Backend Service is where the Ingress sends traffic after identifying the appropriate routing rule. Each rule typically specifies a backend service, which then forwards traffic to Pods. This separation between the external and internal network layers provides greater flexibility for applications. The backend can be an API, web server, or any other application running within Kubernetes.

Load Balancer / NodePort

This is the initial entry point for external traffic to reach the Ingress Controller. In cloud environments, the controller can be exposed as a LoadBalancer, allowing traffic from the Internet to easily enter the cluster. In on-premises environments, NodePort can also be used to route traffic to the controller. The Load Balancer only serves as the entry point, while the Ingress Controller handles the actual traffic processing and routing logic.

How Does Kubernetes Ingress Work?

The Ingress traffic-processing workflow consists of several steps, but it takes place very quickly. First, when a user sends an HTTP/HTTPS request to the application's domain, the request passes through a Load Balancer or NodePort to reach the Ingress Controller. The controller analyzes request information, such as the domain, path, or HTTP method, to find the corresponding rule in the Ingress Resource.

Once a matching rule is found, the controller selects the appropriate backend service and forwards the request. The service then sends the request to the backend Pods using Kubernetes' internal load-balancing mechanism. After the Pod processes the request, the response travels back through the controller and Load Balancer to the user. The entire process occurs within a very short period and generally has minimal impact on application performance.

Key Features of Kubernetes Ingress

Ingress is a powerful tool because of its ability to handle various routing scenarios and complex network configurations. Below are some of the key features that make Ingress a standard routing solution in Kubernetes:

- Host-based routing: This feature allows you to use multiple domains or subdomains to map to different services within a cluster. It is particularly useful when deploying multiple independent applications while sharing a single entry point. The Ingress Controller matches the host specified in the HTTP header and accurately routes traffic to the corresponding service.

- Path-based routing: Ingress also supports path-based routing, allowing multiple applications to share the same domain while being separated by URL paths. For example, /api can route to one service, while /web routes to another. This configuration is highly effective for modular or microservices-based applications that need to separate traffic flows.

- SSL/TLS termination: Ingress allows you to centrally manage SSL certificates instead of configuring them separately for each service. The controller decrypts incoming traffic and forwards requests to the backend service over the internal network. This both enhances security and reduces the processing burden on backend services.

- URL rewriting: Many backend applications have a path structure that differs from their public URL structure. Ingress supports URL rewriting to ensure that requests are handled correctly. The controller rewrites the original path into the appropriate path before forwarding traffic to the backend. This feature is particularly useful for legacy applications.

- HTTP → HTTPS redirection: Ingress can automatically redirect all HTTP requests to HTTPS, helping improve application security. This feature can be enabled easily through annotations in the Ingress configuration resource.

- Canary releases & traffic splitting: With certain controllers, Ingress allows traffic to be distributed across different application versions according to specified percentages. This is particularly useful for canary deployments or A/B testing, allowing you to validate a new version before completing the full rollout.

Benefits of Using Kubernetes Ingress

Ingress provides numerous benefits for application deployment. First, it helps reduce costs because you do not need to create a separate load balancer for every service. Ingress also provides centralized routing and SSL management, reducing operational complexity and potential configuration risks. In addition, Ingress supports a wide range of advanced features, making the system more flexible.

Furthermore, in microservices environments, having a single entry point makes traffic more secure and easier to control. You can also integrate Ingress with monitoring and logging tools to build a comprehensive observability system. Ingress has therefore become an essential component of many cloud-native environments.

Limitations of Using Kubernetes Ingress

Despite its many advantages, Ingress also has some limitations. First, you need to install an Ingress Controller, and different controllers may behave differently, meaning administrators need to understand how to configure each implementation correctly. In addition, Ingress primarily supports HTTP/HTTPS, while TCP/UDP support is more limited and may require additional CRDs.

Some controllers also require extensive use of annotations and complex configurations, which can make them challenging for beginners and increase the risk of configuration errors. Furthermore, as a system scales, managing a large number of routing rules can become increasingly difficult. However, these limitations can be addressed through proper architecture and planning from the beginning.

Ingress vs. API Gateway

Conclusion

Kubernetes Ingress is one of the most important components when deploying large-scale Kubernetes environments. With powerful routing capabilities, SSL support, load balancing, and advanced features, Ingress enables you to manage traffic efficiently while optimizing costs.

If your organization wants to deploy Kubernetes quickly, reliably, and with lower operational costs, consider Viettel IDC's Viettel Open Kubernetes Service (vOKS) here. This Kubernetes platform service enables software developers to easily build, deploy, scale, and manage applications packaged as containers:

https://viettelidc.com.vn/en/viettel-kubernetes-service

For consultation and information about Viettel’s services, you can contact Viettel IDC directly through the following channels:

- Hotline: 1800 8088 (toll-free)

- Fanpage: https://www.facebook.com/viettelidc

- Website: https://viettelidc.com.vn