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Kubernetes Ingress Controller Design
The Kubernetes Ingress Controller configures Kong
using Ingress resources created inside a Kubernetes cluster.
The Kubernetes Ingress Controller is made up of two high level components:
- Kong, the core proxy that handles all the traffic
- Controller Manager, a series of processes that synchronize the configuration from Kubernetes to Kong
The Kubernetes Ingress Controller performs more than just proxying the traffic coming
into a Kubernetes cluster. It is possible to configure plugins,
load balancing, health checking and leverage all that Kong offers in a
The following figure shows how it works:
The Controller Manager listens for changes happening inside the Kubernetes
cluster and updates Kong in response to those changes to correctly
proxy all the traffic.
Kong is updated dynamically to respond to changes around scaling,
configuration changes, failures that are happening inside a Kubernetes
Kubernetes resources are mapped to Kong resources to correctly
proxy all the traffic.
The following figure describes the mapping between Kubernetes concepts
to Kong’s configuration:
Let’s go through how Kubernetes resources are being mapped to Kong’s
- An Ingress
resource in Kubernetes defines a set of rules for proxying
traffic. These rules corresponds to the concept of Route in Kong.
- A Service
inside Kubernetes is a way to abstract an application that is
running on a set of pods.
This maps to two objects in Kong: Service and Upstream.
The service object in Kong holds the information on the protocol
to use to talk to the upstream service and various other protocol
specific settings. The Upstream object defines load-balancing
and health-checking behavior.
- Pods associated with a Service in Kubernetes map as a Target belonging
to the Upstream (the upstream corresponding to the Kubernetes
Service) in Kong. Kong load balances across the Pods of your service.
This means that all requests flowing through Kong are not directed via
kube-proxy but directly to the pod.
For more information on how Kong works with Routes, Services, and Upstreams,
please see the Proxy
and Load balancing references.