Kubernetes Ingress

Kubernetes is an open-source application that helps you manage and scale your containerized applications automatically. When you containerize an application, how do you make it available to the users (or customers)? How do you let them access your containerized application? This is where Kubernetes Ingress comes in. Once your application is running inside the Kubernetes cluster, you need a way to expose it to the outside world (users, APIs, browsers, and more). This is managed efficiently by Kubernetes Ingress. 

In this article, we will cover what ingress is and its role within the Kubernetes ecosystem. We will also understand the role of Ingress controllers like Nginx and AWS ALB. Finally, we will examine how Ingress compares to other methods, such as load balancers and egress, and determine when each should be used. 

What is Kubernetes Ingress?

Fundamentally, Kubernetes Ingress is a resource that manages how external users access the services running inside the Kubernetes cluster. You can think of it as a gateway that controls the HTTP or HTTPS requests from the outside world to your applications. It simplifies the traffic while maintaining control over security and routing. Ingress is the middleman between a user and the service that defines the rules of routing.

As you can see in the picture above, ingress sits between the Pods and the outside world in the Kubernetes ecosystem. Pods are the units where the application is actually running. Kubernetes ingress is smarter as compared to other exposure methods. It does not expose arbitrary ports or protocols and focuses primarily on HTTP and HTTPS traffic, which makes it particularly suitable for web applications and APIs.

Why Kubernetes Ingress is Needed?

Before Kubernetes Ingress, multiple ways would act as a bridge between the application cluster and the outside world. To name a few, they were NodePort, LoadBalancer, or directly through web servers like Nginx. However, there were many complexities attached to these methods that made them difficult to scale and inefficient.

This is where Kubernetes Ingress compares better. It gives you better control over routing and security, while also simplifying external access. With Kubernetes Ingress, you can:

• Route traffic intelligently to different services based on URL paths or hostnames, without creating multiple load balancers.
• Terminate SSL/TLS connections, and enable HTTPS support centrally, eliminating the need to configure certificates on each service separately.
• Implement load balancing across services or pods for better performance and high availability.
• Centralize traffic management in a declarative, Kubernetes-native way, making maintenance and scaling much easier.

Ingress acts as the single entry point that handles all external HTTP/HTTPS requests smartly based on your rules. 

Key components of Kubernetes Ingress

Kubernetes ingress has two main components that work together. Let us look at them in detail:

1. Ingress Resource

The Ingress Resource is a Kubernetes API object that defines how external traffic should be routed to your services. You can think of it as the “traffic plan” or set of rules for your applications. It has all the details of configurations and information that would be needed for the YAML file. 

With an Ingress Resource, you can:

• Route traffic based on hostnames (e.g., app.example.com) or URL paths (e.g., /shop → Service A, /blog → Service B).
• Specify TLS certificates to enable HTTPS for secure communication.
• Add annotations to enable features like authentication, redirects, or rate limiting.
  

In short, an Ingress resource describes to the controller what should happen to incoming HTTP and HTTPS requests. It is simply a rule book that the resource follows when taking routing actions.

2. Ingress Controller

The ingress controller is the one responsible for enforcing the rules defined in the Ingress resource. It actually waits and monitors the Kubernetes cluster for the Ingress resource and then configures the underlying network, implementing those rules. 

Some of the popular ingress controllers are:

• AWS Load Balancer Controller: This integrates with AWS ALB for Kubernetes clusters and looks for Ingress resources.
• The Nginx Ingress Controller is also widely used as it is well-documented and easy to manifest through a GitHub repository.

To summarize its responsibilities, an ingress controller is actually responsible for:

• Creating a load balancer and then setting up a path for external routing.
• It may also terminate a TLS connection if stated in the ingress resource.

Core features and functionality of Kubernetes Ingress 

By now, you might have a basic understanding and a rough idea of the primary features and functionalities of Kubernetes Ingress. In this section, we will list all its primary functions along with other unique functions in one place so that it is easy for you to browse.

1. Host-Based Routing

• The primary feature of Kubernetes Ingress is host-based routing, making it smart. This means that, based on the domain name user requests, ingress routes are created that directly request the required server.
• The same services within a Kubernetes cluster are assigned different domain names through which they are accessed. A single ingress handles all of this quite smoothly. This makes managing multiple applications much easier, especially when you’re running several services under one domain or project.

2. Path-Based Routing

• Now, what happens when you have multiple parts of your application under the same host? In such a case, Kubernetes Ingress uses routing based on URL path after the domain name.
• This means that instead of deploying multiple load balancers or exposing each service separately, you can control everything from one Ingress file. It keeps your setup organized and reduces cost and complexity.

3. TLS Termination

• You must be aware that when a user tries to access a website through HTTPS, a TLS connection is established. This also leads to your data being encrypted using a TLS certificate. Normally, every service would need its own certificate configuration, which can be hard to maintain.
• With Kubernetes Ingress TLS termination, you can manage HTTPS connections centrally at the Ingress level. It decrypts the traffic and forwards the request to the designated service. This not only simplifies certificate management but also reduces the workload on individual services, since encryption and decryption are handled at the Ingress layer.

4. Single IP for Multiple Services

• A single Ingress resource can expose multiple services using one external IP address. It removes the need for having multiple load balancers, hence multiple IP addresses, for different services. 
• Your entire set of web apps can live behind one IP address, while still being accessed individually through different routes or domains.

Kubernetes Ingress vs. Load Balancer vs. Nodeport

NodePort can be useful for quickly experimenting or developing a small internal application because it is easy to configure, but limited in functionality. LoadBalancer is suitable for exposing a single production service that needs load balancing; however, each service will incur additional costs. Ingress is well-suited for a modern, containerized application that consists of many services, provides central traffic routing, host/path-based routing, and TLS termination, and can do this all under a single external IP address. Ingress is a powerful addition to NodePort and LoadBalancer, and serves as a scalable, cost-efficient, and secure gateway for external traffic into a Kubernetes cluster.

Implementation of Kubernetes Ingress

In this hands-on Kubernetes Ingress tutorial, we’ll walk through the steps to expose a sample application using Ingress, including routing traffic with rules and verifying that everything works as expected.

Prerequisites

Before starting, make sure you have:

• A running Kubernetes cluster (local, like Minikube, or cloud-based)

• kubectl is installed and configured. You can check if it is installed or not by running this command “kubectl version –client”. 

• Basic understanding of Pods and Services

Step 1: Deploy a Sample Application and Service

First, let’s deploy a simple web application. Here’s an example using Nginx:

apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    app: nginx
spec:
  containers:
  - name: nginx
    image: nginx:latest
    ports:
    - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  selector:
    app: nginx
  ports:
  - protocol: TCP
    port: 80
    targetPort: 80
  type: NodePort

Since we have named the above YAML file as nginx-svc.yaml, apply it with:

kubectl apply -f nginx-svc.yaml

This creates a Pod running Nginx and a Service that exposes it internally in the cluster.

Step 2: Create an Ingress Manifest

Next, we define an Ingress resource to expose the application externally. We will name this file nginx-ingress.yaml.

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: nginx-ingress
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  ingressClassName: nginx
  rules:
  - host: nginx.example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: nginx-service
            port:
              number: 80

Key points:

• ingressClassName: nginx tells Kubernetes which Ingress Controller to use.
• Traffic to nginx.example.com will be routed to nginx-service.

Step 3: Apply the Ingress and Verify Traffic Routing

Now, to apply the Ingress manifest, enter the following command in the Bash shell:

kubectl apply -f nginx-ingress.yaml

Verify that the Ingress has been created and the rules are in place using the following commands:

kubectl get ingress
kubectl describe ingress nginx-ingress

Verify your pods and services as well to make sure that everything is working well using the following commands:

kubectl get pods
kubectl get svc
kubectl get ingress

Step 4: Map the Hostname Locally

Finally, access your application using the host defined (nginx.example.com). Since we are using Minikube, we must add an /etc/hosts entry to map nginx.example.com to your Minikube IP. To do that, first use this command to find the IP address of your Kubernetes cluster.

minikube ip

Whatever IP address you get, copy or note it somewhere. Now, go to the following file using the path C:WindowsSystem32driversetchosts. Scroll to the bottom and map the IP address you noted to the website using the following line.

192.168.49.2   nginx.example.com

Save the file and close. Ingress will be used to route the traffic through your Nginx application. This is how Ingress simplifies access and routing for external users.

Best Practices and Common Pitfalls When Using Kubernetes Ingress

You have a basic understanding of how you can use Ingress resources in Kubernetes. It is important that you carefully input the IP addresses, as they can significantly impact the security and reliability. That is why it is important to follow the right practices to ensure stable traffic routing, while ignoring key features may lead to inconsistent behavior across environments.

Kubernetes Ingress Best Practices

• Secure the Ingress with TLS and Authentication: Always ensure that you have enabled TLS termination to encrypt traffic between the client and the cluster. For even more protection, you should also integrate authentication mechanisms such as OAuth, JWT, or mTLS. This prevents maximum unauthorized access and sees to it that the data is secure.
  
• Define Clear Path and Host Rules: Remember to use exact path definitions that are also non-overlapping for multi-domain environments. Do the same for host-based routing. Maintain consistent naming conventions for better understandability of developers. Also, organize Ingress resources by namespace to improve traceability and reduce routing conflicts.
  
• Validate Controller Compatibility and Versions: Different Ingress controllers (NGINX, HAProxy, Traefik, etc.) may interpret annotations or path types differently. Always check version compatibility with your Kubernetes cluster and controller documentation before deployment. Aligning these versions ensures consistent behavior and avoids deprecation issues.
  

Common Pitfalls to Avoid

• Ignoring TLS Certificate Renewal and Secrets Management: When using TLS, developers usually forget that they have set up a TLS environment. Expired certificates or mismanaged secrets can lead to downtime. Automate certificate renewal using tools like Cert-Manager and enforce secret rotation policies.
• Ignoring Controller Behavior: Ingress controllers can deal with redirect requests as well as default backends in various ways, depending on the cloud provider or on-prem cluster. Testing had to happen in staging, because otherwise, you could see strange routing behavior in production. 
• Ignoring Namespace Isolation and Resource Names: Defining Ingress objects across namespaces with the same or similar names leads to ambiguity in routing. Make sure you’re being consistent in your naming convention (for example: service-name-env-domain) and consider logically isolating your environments by using dedicated namespaces.

Limitations of Ingress

• Restricted to HTTP and HTTPS Traffic: Ingress resources only support Layer 7 (HTTP/HTTPS) routing out of the box. For routing TCP, UDP, and other protocols, including gRPC, you will need additional configuration or separate resources, including a Service of type LoadBalancer and an IngressRoute (depending on the controller). 
• Controller and Feature Variability: The functionality of an Ingress resource is heavily dependent on the chosen Ingress controller (NGINX, Traefik, Istio, etc.). Controllers vary in the features, supported annotations, and configuration syntax, which reduces portability and warrants environment-specific tuning. 
• Advanced Routing and Security Rule Complexity: Ingress works well for basic routing, but configuring for advanced use cases (such as weighted routing, A/B test, or dynamic header change/addition) is cumbersome. Many use cases warrant a comprehensive API gateway or service mesh to get the required level of control. 
• Scaling and Observability Overhead: Scale introduces complexity for environments with hundreds of routes or thousands of services that take advantage of Ingress resources. Things like monitoring, debugging, and traffic tracing across multiple controllers and namespaces will require third-party observability tools.

Conclusion

To conclude, in this article, you understood everything related to Kubernetes Ingress that a beginner should know. We explained what ingress is and why it is needed in Kubernetes. Then we dived deep into its key features and functionality, along with its components. Finally, we gave an easy-to-understand Kubernetes ingress tutorial that you can run yourself and learn. 

By following the Kubernetes Ingress best practices and being aware of its common pitfalls and limitations, you can design secure, efficient, and scalable routing for your applications. As you gain more experience, try exploring advanced Ingress configurations or integrating service meshes for even greater control and flexibility.

Kubernetes Ingress – FAQs