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Migrating Ingress to Gateway

As the name states, the Kong Ingress Controller is an ingress controller. Right from the early stage of the Gateway API development, the Kong Ingress Controller supports the Gateway API as well, as an alternative to the ingress resources. Since the Gateway API graduation, happened in late 2023, the Kong Ingress Controller promoted the Gateway API as the preferred way of configuring the Kong Gateway in Kubernetes.

The IngressToGateway tool

Kong contributed to the kubernetes-sigs project ingress2gateway by creating a Kong provider able to convert ingress resources into Gateway resources. The ingress2Gateway tool provides a unique print command that gets ingress resources and displays the Gateway API equivalent. The output of such an operation can be either directly applied to the cluster, or into a file, to have a new set of yaml files containing the converted configuration.

Supported Ingress features and annotations

Here is a list of all the ingress features, along with the Gateway API equivalent support.

Kong Ingress Controller provides an extensive set of annotations. This is the list of the features supported by the Ingress2Gateway’s Kong provider. Such a list is improved over time.

Annotation name	Conversion
REQUIRED `kubernetes.io/ingress.class`	`gateway.spec.gatewayClassName`
`konghq.com/methods`	`httpRoute.spec.rules[].matches[].method`
`konghq.com/headers.*`	`httpRoute.spec.rules[].matches[].headers`
`konghq.com/plugins`	`httpRoute.spec.rules[].matches[].headers`

Features

kubernetes.io/ingress.class

Annotation description

If configured on an Ingress resource, this value is used as the gatewayClassName set on the corresponding generated Gateway.

konghq.com/methods

Annotation description

If configured on an Ingress resource, this value is used to set the HTTPRoute method matching configuration. Since many methods can be set as a comma-separated list, each method creates a match copy. All the matches belonging to the same HTTPRoute rule are put in OR.

konghq.com/headers.*

Annotation description

If configured on an Ingress resource, this value sets the HTTPRoute header matching configuration. Only exact matching is supported. Because many values can be set for the same header name as a comma-separated list, each header value is used to create a match copy. All the matches belonging to the same HTTPRoute rule are put in OR.

konghq.com/plugins

Annotation description

If configured on an Ingress resource, this value attaches plugins to routes. Plugin references are converted into HTTPRoute ExtensionRef filters. Each plugin is converted into a different reference to a KongPlugin or KongClusterPlugin.