What is Ingress Controller?
An Ingress Controller is a Kubernetes component that watches Ingress resources and configures a reverse proxy to route external HTTP and HTTPS traffic to services inside the cluster.
An Ingress Controller is a specialized pod or set of pods within a Kubernetes cluster that implements the Ingress API resource. It acts as a reverse proxy and load balancer, handling external HTTP and HTTPS requests and forwarding them to the appropriate internal services based on rules defined in Ingress resources.
The controller continuously watches the Kubernetes API server for Ingress objects. When a new Ingress rule is created or updated, the controller automatically reconfigures the underlying proxy server (e.g., NGINX, HAProxy, Traefik, Envoy) to apply routing rules, TLS termination, and virtual hosting. This allows multiple services to be exposed through a single external IP address or hostname, reducing the need for separate load balancers per service.
Ingress Controllers are typically deployed as a Deployment or DaemonSet and exposed externally via a Service of type LoadBalancer or NodePort. They integrate with cloud-provider load balancers to receive traffic from the internet. The Ingress resource itself is a cluster-scoped API object that defines routing, SSL certificates, and path-based or host-based rules. Without an Ingress Controller, Ingress resources have no effect; the controller is the actual implementation that makes the abstraction work.
Key facts
- An Ingress Controller is required to make Kubernetes Ingress resources functional.
- Popular implementations include NGINX Ingress Controller, HAProxy Ingress, Traefik, and Envoy-based Contour.
- The controller dynamically updates its reverse proxy configuration as Ingress rules are added, modified, or removed.
- Ingress Controllers often terminate TLS/SSL and support load balancing across multiple backend pods.
- They are typically deployed as a DaemonSet or Deployment with a Service of type LoadBalancer for external access.
How it works in practice
Related terms
References
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