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Kubernetes Ingress Controller

Custom Resources

Custom Resources in Kubernetes allow controllers to extend Kubernetes-style declarative APIs that are specific to certain applications.

A few custom resources are bundled with the Kubernetes Ingress Controller to configure settings that are specific to Kong and provide fine-grained control over the proxying behavior.

The Kubernetes Ingress Controller uses the configuration.konghq.com API group for storing configuration specific to Kong.

The following CRDs allow users to declaratively configure all aspects of Kong:

KongIngress

The Ingress resource in Kubernetes is a fairly narrow and ambiguous API, and doesn’t offer resources to describe the specifics of proxying. To overcome this limitation, KongIngress Custom Resource is used as an “extension” to the existing Ingress API to provide fine-grained control over proxy behavior. In other words, KongIngress works in conjunction with the existing Ingress resource and extends it. It is not meant as a replacement for the Ingress resource in Kubernetes. Using KongIngress, all properties of Upstream, Service and Route entities in Kong related to an Ingress resource can be modified.

Once a KongIngress resource is created, you can use the configuration.konghq.com annotation to associate the KongIngress resource with an Ingress or a Service resource:

  • When the annotation is added to the Ingress resource, the routing configurations are updated, meaning all routes associated with the annotated Ingress are updated to use the values defined in the KongIngress’s route section.
  • When the annotation is added to a Service resource in Kubernetes, the corresponding Service and Upstream in Kong are updated to use the proxy and upstream blocks as defined in the associated KongIngress resource.

The below diagram shows how the resources are linked with one another:

Associating Kong Ingress

KongPlugin

Kong is designed around an extensible plugin architecture and comes with a wide variety of plugins already bundled inside it. These plugins can be used to modify the request/response or impose restrictions on the traffic.

Once this resource is created, the resource needs to be associated with an Ingress, Service, or KongConsumer resource in Kubernetes. For more details, please read the reference documentation on KongPlugin.

The below diagram shows how you can link KongPlugin resource to an Ingress, Service, or KongConsumer:

   

KongClusterPlugin

This resource requires the kubernetes.io/ingress.class annotation.

KongClusterPlugin resource is exactly same as KongPlugin, except that it is a Kubernetes cluster-level resources instead of being a namespaced resource. This can help when the configuration of the plugin needs to be centralized and the permissions to add/update plugin configuration rests with a different persona than application owners.

This resource can be associated with Ingress, Service or KongConsumer and can be used in the exact same way as KongPlugin.

A namespaced KongPlugin resource takes priority over a KongClusterPlugin with the same name.

KongConsumer

This resource requires the kubernetes.io/ingress.class annotation. Its value must match the value of the controller’s --ingress-class argument, which is “kong” by default.

This custom resource configures Consumers in Kong. Every KongConsumer resource in Kubernetes directly translates to a Consumer object in Kong.

TCPIngress

This resource requires the kubernetes.io/ingress.class annotation. Its value must match the value of the controller’s --ingress-class argument, which is “kong” by default.

This Custom Resource is used for exposing non-HTTP and non-GRPC services running inside Kubernetes to the outside world via Kong. This proves to be useful when you want to use a single cloud LoadBalancer for all kinds of traffic into your Kubernetes cluster.

It is very similar to the Ingress resource that ships with Kubernetes.

KongCredential (Deprecated)

Once a KongConsumer resource is created, credentials associated with the Consumer can be provisioned inside Kong using KongCredential custom resource.

This Custom Resource has been deprecated and will be removed in a future release. Instead, please use secret-based credentials.

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