Kubernetes has become synonymous with container technology today. It facilitates easy deployment and high scalability, because of which many organizations are moving their production workloads to Kubernetes. But as the application grows and you keep adding new clusters and nodes, things start slipping out of hand. You will have to depend on tools to control your production environment. It is especially true for network management, which becomes complicated and opens up security risks. For efficient traffic management, you will need Ingress Controllers. These tools automate service access to external networks within the Kubernetes cluster.
What is an ingress controller?
The ingress controller is a load balancer used in Kubernetes environments to route traffic within clusters. It forms a link between external networks and Kubernetes services based on the rules defined by Ingress. These rules typically dictate how traffic from the internet in the form of HTTP and HTTPS protocols accesses application services.
An ingress controller is typically tasked with –
- Adjust load balancing rules based on the newly added or terminated Kubernetes pods.
- Monitor pods to keep track of changes in pod dynamics.
- Manage external traffic and direct it toward the right containers.
- Facilitate communication of clusters with external services through in-cluster egress.
- Deploy ingress resources and config files through Kubernetes API and use Kubectl to run commands.
How does an ingress controller work?
In Kubernetes, pods are the smallest computing units created and grouped under a service. These services ensure external pods reach out to the pods it is attached to through a load-balancing act. However, the catch here is that these services are not accessible to traffic coming from the internet. The networking becomes even more challenging with the pods’ ephemeral nature. They are constantly added and terminated as the application scales up and down. This is where ingress controllers add value. They form a gateway for external requests to access applications based on the rules ingress defined for user access.
Ingress controllers are more than just traffic managers. They secure your Kubernetes clusters by imposing strict rules to control authentication and access and implementing Transport Layer Security (TLS) keys and certificates.
5 Open Source Ingress Controllers
Kubernetes ecosystem allows you a variety of ingress controllers to pick from. By default, Kubernetes supports AWS, GCE, and nginx ingress controllers. If you plan to use any other controllers, you must deploy them in your cluster. Below we have listed five important open-source ingress controllers.
1. Istio Ingress
Istio is a service mesh solution that enables Kubernetes to manage traffic and route it across the cluster efficiently. Launched by Google, IBM, and Lyft, Istio enables you to improve traffic routing, monitoring, and security for cloud-native applications.
One key benefit of Istio is isolating traffic management by moving it into the platform layer as a cloud-native infrastructure. As a language-independent tool, Istio can easily automate networking. Although Istio is primarily a service mesh, it offers extended capabilities of ingress control like applying authentication, monitoring, tracking metrics, and tracing headers.
HAProxy (High Availability Proxy) is one of the popular ingress controllers. It is a single-purpose tool that supports load balancing to distribute workloads across servers. It supports the three common load balancing techniques – Round-Robin, IP hash, Least Connection, and methodologies like static-RR, the first source, and url_param.
HAProxy is ideal for web applications with high traffic volumes as it provides consistent load balancing so you don’t experience downtime or outages. It has comprehensive security features to reduce the attack surface by isolating itself with chroot. It also evaluates incoming traffic by monitoring the client’s behavior to identify malicious requests.
Traefik is a cloud-native HTTP reverse load balancer that can be integrated with any Kubernetes ecosystem. It began as an application proxy that automates service discovery routing requests within a microservices architecture. Now it is a dynamic ingress controller that supports TCP, HTTP, and HTTP protocols. It is one of the leading load balancers that allows you to run multiple instances with different load-balancing algorithms, ensuring high availability.
Written in Go, it provides a user-friendly UI that visualizes controller and Kubernetes metrics. Traefik automates configuration setup deriving it straight from the environment. It ensures secure communication by filtering the traffic through Let’s Encrypt certificate system. You can add a security layer to your network with HTTPS/2 protocol support.
NGINX is the ingress controller that is a part of the official Kubernetes distribution. It provides HTTP/S routing, socket support, tracing, content-based routing, TLS/SSL termination, authentication, and SSL capabilities. It has become a default ingress controller for beginners since you don’t have to depend on external modules.
While the open-source variant of NGINX ingress controller is a default option if you’re just starting, you will not have advanced load balancing algorithms. Its business version, NGINX Plus, lets you make dynamic design changes without reloading. It offers added security features like health checks and TCP/UDP traffic.
5. Kong Ingress
Built upon the NGINX ingress controller, Kong Ingress started as an API gateway routing and managing API requests. Today it is a fully functional ingress controller offering more capabilities than open-source NGINX. Some features include RPC support, health checks on load balancers, and request authentication. With Kong, you can expand the controller functionality with added modules and plugins.
Kong Ingress offers a premium variant besides the open-source, which opens up an extended ecosystem of plugins and a dashboard to manage traffic.
Understand what is right for you
Kubernetes offers support to a wide range of ingress controllers giving you the flexibility to work with one you like. Every option we listed above is a popular ingress controller offering comprehensive traffic management capabilities. However, instead of pitching them against each other to select the best one, we suggest you understand your Kubernetes environment and evaluate ingress controllers based on your requirements. NGINX is a default option but offers limited features as a part of its open-source version. Kong, on the other hand, offers more capabilities than through plugins. There are similar differences between Istio, HAProxy, and Traefik.