What is a Kubernetes Ingress controller?

Modern businesses rely heavily on distributed applications and workloads built from dozens or hundreds of microservices. Without proper traffic orchestration, each service would require its own public endpoint, which would require significant management and security issues.

For example, a healthcare platform might need separate access points for patient portals, provider dashboards, billing systems and compliance reporting—an approach that becomes expensive and operationally complex.

A Kubernetes Ingress controller addresses this problem by serving as a load balancer and intelligent traffic router at the application entry point. It establishes a centralized traffic route for external users to access internal services.

The Kubernetes ecosystem offers various Ingress controllers, including open source tools (for example, NGINX, Traefik) available on platforms like GitHub and proprietary solutions designed to meet specific organizational needs.

Initially developed by Google and donated to the Cloud Native Computing Foundation (CNCF) in 2015, Kubernetes now powers essential IT infrastructure for most Fortune 500 companies, making Ingress controller management critical for enterprise operations. According to a 2022 survey, 96% of organizations are using Kubernetes or evaluating this technology for production environments.¹

Before Kubernetes, applications typically ran on dedicated servers or virtual machines (VMs), making scaling expensive and time-consuming. Kubernetes introduced containers—lightweight, portable units that package applications with all their dependencies.

Kubernetes revolutionized DevOps workflows and application deployment by introducing container orchestration at scale. This open source platform automates the deployment, scaling and management of containerized applications across distributed infrastructure, enabling seamless collaboration between development and operations teams.

Kubernetes organizes applications into pods—the smallest deployable units composed of one or more containers (usually Docker containers). These pods run across worker nodes within clusters, while a control plane coordinates all cluster operations. Services provide stable network identities for groups of pods, enabling reliable communication patterns.

Ingress controllers are typically deployed as specialized pods that monitor the cluster state through the Kubernetes API. These controllers track changes in Ingress resources—configuration objects that define traffic routing rules—and automatically update their routing tables to reflect new application deployments or configuration updates.

To understand how Ingress controllers work, it's essential to understand Kubernetes Ingress—the API resource (or Ingress object) that defines routing rules directing external traffic to services within a Kubernetes cluster.

Kubernetes Ingress is distinct from the general term ingress, which refers to the flow of incoming network traffic into a cloud-native, containerized application environment. In Kubernetes, Ingress specifically refers to the set of rules and configurations that manage how incoming traffic is routed to different services. In contrast, ingress in a broader sense simply refers to any traffic entering a system (as opposed to egress, which refers to traffic flowing out of the system).

Read more about ingress versus egress in Kubernetes.

Kubernetes Ingress provides a declarative approach to managing external access to services within a Kubernetes cluster. Instead of exposing individual services (for example, NodePort, LoadBalancer services) directly to the internet, Ingress creates a controlled access layer that intelligently routes requests based on multiple criteria. This capability enables the efficient management of external traffic to services, typically exposed by using ClusterIP within the Kubernetes cluster.

Kubernetes Ingress operates through two complementary components.

Ingress resources (also referred to as Kubernetes resources or Kubernetes API objects) define routing rules. They are defined in YAML or JSON, specifying ingress rules, SSL certificates, authentication requirements and traffic policies.

For example, users can use the ingressClassName field to determine which Ingress controller should manage the resource, allowing traffic direction to a specific controller when multiple controllers exist in a cluster.

Ingress controllers are software components that read and apply configuration rules, acting as reverse proxies with advanced traffic management capabilities.

Traditional Layer 4 load balancers, such as those for TCP, UDP and HTTP/HTTPS routes, distribute traffic based solely on IP addresses and ports. In contrast, a Kubernetes Ingress controller operates at Layer 7 (the application layer), enabling more sophisticated routing.

Leveraging the Kubernetes Ingress API and features like HTTPRoute, the Ingress controller makes routing decisions based on detailed HTTP-specific attributes, such as:

• URL paths and hostnames
• HTTP headers and methods
• Request content and cookies
• Authentication tokens and user context

These decisions are based on configuration rules that dictate the routing policies and other requirements. Ingress controllers continuously monitor changes in these configurations, automatically updating routing behavior without manual intervention, ensuring seamless traffic distribution and security management.

Kubernetes clusters can run multiple Ingress controllers simultaneously, each handling different traffic types or applications. Each controller operates in an event-driven manner, responding to changes in Ingress resources by reading specifications, annotations and metadata, then converting them into executable routing instructions.

Kubernetes Ingress controllers examine incoming requests and make routing decisions based on predefined rules, such as hostnames and DNS names. They handle HTTP and HTTPS traffic, perform SSL termination and make intelligent load balancing decisions across multiple service instances.

Kubernetes Ingress controllers continuously monitor the Kubernetes API for changes to Ingress resources across namespaces. Whether these changes are applied through kubectl, CI/CD pipelines or other tools (for example, Helm, Terraform), the controller automatically updates routing rules without manual intervention or service restarts.

Built into most Kubernetes Ingress controllers, load balancing functionality distributes incoming requests across multiple instances of the same service, ensuring optimal performance and preventing any single instance from becoming overwhelmed.

Modern Kubernetes Ingress controllers include sophisticated SSL/TLS management capabilities, such as TLS termination, automatic certificate provisioning, renewal and secure communication enforcement.

Advanced Kubernetes Ingress controllers continuously monitor the health of backend services and automatically route traffic away from failing instances to ensure high availability and improved user experience.

• Infrastructure consolidation: Traditional architectures often require dedicated load balancers for each application, creating significant hardware and operational costs. Ingress controllers enable organizations to consolidate multiple applications behind shared infrastructure, reducing load balancing costs and improving resource utilization.
• Accelerated development cycles: Development teams can deploy and test new features without involving network administrators or configuring external load balancers. Ingress controllers support GitOps workflows where routing changes are managed through version control and automated deployment pipelines.
• Enhanced observability: To provide enhanced observability, modern Ingress controllers provide detailed analytics about application usage patterns, user behavior and performance bottlenecks. This visibility enables data-driven decisions about capacity planning, feature adoption and user experience optimization.
• Automated security enforcement: Rather than configuring security policies across multiple systems, organizations can enforce authentication, authorization, rate limiting, WAF (web application firewall) rules and DDoS protection through Ingress controller policies. Security updates can be deployed instantly across all applications.
• Cloud portability: Unlike cloud-specific load balancing services, Ingress controllers provide consistent functionality across different cloud providers and on-premises infrastructure. Applications can be migrated between environments without architectural changes.
• Dynamic scaling capabilities: Ingress controllers can automatically adjust routing patterns based on real-time traffic conditions, back end capacity and configured policies. This feature enables sophisticated traffic shaping that adapts to changing business conditions.

• Performance considerations: All external traffic flows through Ingress controllers, making them potential bottlenecks in production environments. Organizations must carefully plan for capacity, implement proper monitoring and design redundancy strategies to ensure high availability.
• Learning curve and operational overhead: Teams need to develop expertise in Kubernetes networking concepts, YAML configuration management and troubleshooting distributed systems, which can require significant training and operational adjustment.

Choosing the right Kubernetes Ingress controller depends on organizational requirements, existing infrastructure and team capabilities. Each implementation offers distinct advantages for specific use cases:

• NGINX Ingress controller: The most widely adopted option, the NGINX Ingress controller (ingress-nginx), offers enterprise-grade performance and extensive customization capabilities. NGINX's mature ecosystem provides comprehensive documentation, commercial support options and proven scalability.
• Traefik Ingress controller: Traefik is designed for modern cloud-native environments, with an emphasis on automatic service discovery and ease of use. Traefik excels in dynamic environments where Kubernetes services frequently change, offering built-in integration with service meshes and container registries.
• HAProxy Ingress controller: Built on the industry-standard HAProxy load balancer, the HAProxy Ingress controller provides robust performance for high-traffic scenarios. This controller enables advanced load-balancing algorithms, detailed statistics and fine-grained traffic control.
• Istio Gateway: As part of the comprehensive Istio service mesh platform, Istio Gateway features advanced traffic management, security and observability features. Istio Gateway also supports sophisticated capabilities, such as traffic splitting, fault injection and distributed tracing.
• Cloud provider solutions: Major cloud providers offer optimized Ingress controllers that integrate deeply with their platforms. AWS Load Balancer controller, Google Cloud Load Balancer, Azure Application Gateway Ingress controller and IBM Cloud Application Load Balancer provide seamless integration with cloud-native services, automated scaling and simplified billing.
• Envoy-based controllers: Ingress controllers built on the Envoy proxy, including Ambassador and Emissary-Ingress, deliver high-performance traffic management with advanced observability features. These solutions often include built-in authentication, rate limiting and API gateway functionality, making them suitable for organizations building comprehensive API management strategies.