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Using Plugin Resources

Learn to apply the Kong Ingress Controller KongPlugin and KongClusterPlugin custom resources to other configurations. These resources change how Kong Gateway handles proxied requests. You can configures plugins to modify headers and enforce authentication requirements.

See the concept documentation for more information about the purpose of the KongPlugin resource.

Installation

Follow the deployment documentation to install the Kong Ingress Controller on the Kubernetes cluster.

Installing the Gateway APIs

If you wish to use the Gateway APIs examples, follow the supplemental Gateway APIs installation instructions.

Testing connectivity to Kong Gateway

Ensure that the PROXY_IP environment variable is set to contain the IP address or URL pointing to Kong Gateway. The deployment guide that you used to install the Kong Ingress Controller on the Kubernetes cluster provides the instructions to configure this environment variable.

If everything is set correctly, a request to Kong Gateway returns a HTTP 404 Not Found status code:

curl -i $PROXY_IP

The results should look like this:

HTTP/1.1 404 Not Found
Content-Type: application/json; charset=utf-8
Connection: keep-alive
Content-Length: 48
X-Kong-Response-Latency: 0
Server: kong/3.0.0

{"message":"no Route matched with those values"}

This is expected because Kong Gateway doesn’t know how to proxy the request yet.

Deploy an upstream HTTP application

To proxy requests, you need an upstream application to send a request to. Deploying this echo server provides a simple application that returns information about the Pod it’s running in:

echo "
apiVersion: v1
kind: Service
metadata:
  labels:
    app: echo
  name: echo
spec:
  ports:
  - port: 1025
    name: tcp
    protocol: TCP
    targetPort: 1025
  - port: 1026
    name: udp
    protocol: TCP
    targetPort: 1026
  - port: 1027
    name: http
    protocol: TCP
    targetPort: 1027
  selector:
    app: echo
---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: echo
  name: echo
spec:
  replicas: 1
  selector:
    matchLabels:
      app: echo
  strategy: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: echo
    spec:
      containers:
      - image: kong/go-echo:latest
        name: echo
        ports:
        - containerPort: 1027
        env:
          - name: NODE_NAME
            valueFrom:
              fieldRef:
                fieldPath: spec.nodeName
          - name: POD_NAME
            valueFrom:
              fieldRef:
                fieldPath: metadata.name
          - name: POD_NAMESPACE
            valueFrom:
              fieldRef:
                fieldPath: metadata.namespace
          - name: POD_IP
            valueFrom:
              fieldRef:
                fieldPath: status.podIP
        resources: {}
" | kubectl apply -f -

The results should look like this:

service/echo created
deployment.apps/echo created

Create a configuration group

Ingress and Gateway APIs controllers need a configuration that indicates which set of routing configuration they should recognize. This allows multiple controllers to coexist in the same cluster. Before creating individual routes, you need to create a class configuration to associate routes with:

echo "
apiVersion: networking.k8s.io/v1
kind: IngressClass
metadata:
  name: kong
spec:
  controller: ingress-controllers.konghq.com/kong
" | kubectl apply -f -

ingressclass.networking.k8s.io/kong configured

echo "
---
apiVersion: gateway.networking.k8s.io/v1beta1
kind: GatewayClass
metadata:
  name: kong
  annotations:
    konghq.com/gatewayclass-unmanaged: 'true'

spec:
  controllerName: konghq.com/kic-gateway-controller
---
apiVersion: gateway.networking.k8s.io/v1beta1
kind: Gateway
metadata:
  name: kong
spec:
  gatewayClassName: kong
  listeners:
  - name: proxy
    port: 80
    protocol: HTTP
" | kubectl apply -f -

gatewayclass.gateway.networking.k8s.io/kong created
gateway.gateway.networking.k8s.io/kong created

kubectl get gateway kong

NAME   CLASS   ADDRESS        READY   AGE
kong   kong    203.0.113.42   True    4m46s

Kong Ingress Controller recognizes the kong IngressClass and konghq.com/kic-gateway-controller GatewayClass by default. Setting the CONTROLLER_INGRESS_CLASS or CONTROLLER_GATEWAY_API_CONTROLLER_NAME environment variable to another value overrides these defaults.

Add routing configuration

Create routing configuration to proxy /lemon requests to the echo server:

echo "
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: lemon
  annotations:
    konghq.com/strip-path: 'true'
spec:
  ingressClassName: kong
  rules:
  - host: kong.example
    http:
      paths:
      - path: /lemon
        pathType: ImplementationSpecific
        backend:
          service:
            name: echo
            port:
              number: 1027
" | kubectl apply -f -

ingress.networking.k8s.io/lemon created

echo "
apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: lemon
  annotations:
    konghq.com/strip-path: 'true'
spec:
  parentRefs:
  - name: kong
  hostnames:
  - 'kong.example'
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /lemon
    backendRefs:
    - name: echo
      kind: Service
      port: 1027
" | kubectl apply -f -

httproute.gateway.networking.k8s.io/lemon created

Test the routing rule:

curl -i -H 'Host:kong.example' $PROXY_IP/lemon

The results should look like this:

HTTP/1.1 200 OK
Content-Type: text/plain; charset=utf-8
Content-Length: 140
Connection: keep-alive
Date: Fri, 21 Apr 2023 12:24:55 GMT
X-Kong-Upstream-Latency: 0
X-Kong-Proxy-Latency: 1
Via: kong/3.2.2

Welcome, you are connected to node docker-desktop.
Running on Pod echo-7f87468b8c-tzzv6.
In namespace default.
With IP address 10.1.0.237.
...

If everything is deployed correctly, you should see the above response. This verifies that Kong Gateway can correctly route traffic to an application running inside Kubernetes.

After you test the routing configuration to proxy /lemon, create a second routing configuration to proxy /lime that points to the same Service:

echo "
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: lime
  annotations:
    konghq.com/strip-path: 'true'
spec:
  ingressClassName: kong
  rules:
  - host: kong.example
    http:
      paths:
      - path: /lime
        pathType: ImplementationSpecific
        backend:
          service:
            name: echo
            port:
              number: 1027
" | kubectl apply -f -

ingress.networking.k8s.io/lime created

echo "
apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: lime
  annotations:
    konghq.com/strip-path: 'true'
spec:
  parentRefs:
  - name: kong
  hostnames:
  - 'kong.example'
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /lime
    backendRefs:
    - name: echo
      kind: Service
      port: 1027
" | kubectl apply -f -

httproute.gateway.networking.k8s.io/lime created

Configuring plugins for routing configuration

Kong Gateway plugins can apply to a variety of resources. Plugins apply to different sets of requests depending on what type of resource they are applied to. Applying a plugin an Ingress or HTTPRoute modifies requests that match that resource’s routing rules.

The validating admission webhook is not installed by this guide, but is recommended for all environments. The webhook is required to validate plugin configuration. Not installing the webhook can allow invalid plugin configuration, and invalid plugin configuration will block configuration updates until fixed.

1. Create a KongPlugin resource add-header-route that adds a response header x-added-route: demo.

    echo '
    apiVersion: configuration.konghq.com/v1
    kind: KongPlugin
    metadata:
      name: add-header-route
      annotations:
        kubernetes.io/ingress.class: kong
    config:
      add:
        headers:
        - "x-added-route: demo"
    plugin: response-transformer
    ' | kubectl apply -f -
   

   The results should look like this:

    kongplugin.configuration.konghq.com/add-header-route created
   

2. Associate the plugin with routing configuration by adding a konghq.com/plugins annotation whose value is the name of the KongPlugin.

   Ingress

   Gateway APIs

   kubectl annotate ingress lemon konghq.com/plugins=add-header-route

   kubectl annotate httproute lemon konghq.com/plugins=add-header-route

   The results should look like this:

   Ingress

   Gateway APIs

   ingress.networking.k8s.io/lemon annotated

   httproute.gateway.networking.k8s.io/lemon annotated

3. Test the plugin by sending requests to the routes.

   • Requests that match the lemon rules now includes the plugin header:

      curl -si http://kong.example/lemon --resolve kong.example:80:$PROXY_IP | grep x-added-route
     

     The results should look like this:

      x-added-route: demo
     

   • Requests to the lime rules does not include the plugin header:

      curl -si http://kong.example/lime --resolve kong.example:80:$PROXY_IP | grep x-added-route | wc -l
     

     The results should look like this:

      0
     

Configuring plugins on Service resource

Associating a plugin with a Service applies it to any requests that match a routing rule that uses that Service as a backend.

1. Create a KongPlugin resource add-header-service that adds a response header x-added-service: demo.

    echo '
    apiVersion: configuration.konghq.com/v1
    kind: KongPlugin
    metadata:
      name: add-header-service
      annotations:
        kubernetes.io/ingress.class: kong
    config:
      add:
        headers:
        - "x-added-service: demo"
    plugin: response-transformer
    ' | kubectl apply -f -
   

   The results should look like this:

    kongplugin.configuration.konghq.com/add-header-service created
   

2. Associate the plugin with the Service.

    kubectl annotate service echo konghq.com/plugins=add-header-service
   

   The results should look like this:

    service/echo annotated
   

3. Test the plugin by sending requests to the routes.

   • Requests to the lemon route includes the header from the first plugin:

      curl -si http://kong.example/lemon --resolve kong.example:80:$PROXY_IP | grep x-added-
     

     The results should look like this:

      x-added-route: demo
     

   • Requests to the lime route includes the header from the second plugin:

      curl -si http://kong.example/lime --resolve kong.example:80:$PROXY_IP | grep x-added-
     

     The results should look like this:

      x-added-service: demo
     

   Although both routes use the echo Service, only the lime route applies the echo Service’s plugin. This is because only one instance of a particular plugin can execute on a request, determined by a precedence order. Route plugins take precedence over service plugins, so the lemon route still uses the header from the plugin that you created first.

4. Remove the plugin annotation to remove plugin(s) from a resource.

   Ingress

   Gateway APIs

   kubectl annotate ingress lemon konghq.com/plugins-

   kubectl annotate httproute lemon konghq.com/plugins-

   The results should look like this:

   Ingress

   Gateway APIs

   ingress.networking.k8s.io/lemon annotated

   httproute.gateway.networking.k8s.io/lemon annotated

5. Verify that the plugin is removed by sending requests through the lemon route. It now use the Service’s plugin.

    curl -si http://kong.example/lemon --resolve kong.example:80:$PROXY_IP | grep x-added-
   

   The results should look like this:

    x-added-service: demo
   

Configuring global plugins

Global plugins apply to all requests, regardless of which resources they match. Because this applies across Kubernetes namespaces, global plugins require a cluster-scoped KongClusterPlugin instead of a namespaced KongPlugin.

Although not shown in this guide, you can also apply a KongClusterPlugin to resources using konghq.com/plugins annotations, to reuse plugin configurations across namespaces.

1. Create a cluster plugin. KongClusterPlugin configuration is largely the same as KongPlugin configuration, though this resource uses a different plugin and therefore uses different configuration inside its config key.

    echo "
    apiVersion: configuration.konghq.com/v1
    kind: KongClusterPlugin
    metadata:
      name: auth
      annotations:
        kubernetes.io/ingress.class: kong
      labels:
        global: 'true'
    plugin: key-auth
    config:
      key_in_header: true
      key_in_body: false
      key_in_query: false
    " | kubectl apply -f -
   

   The results should look like this:

    kongclusterplugin.configuration.konghq.com/auth created
   

   The global='true' label tells Kong Ingress Controller to create a global plugin. These plugins do not need annotations on other resources for them to take effect, but they do need an ingress.class annotation for the controller to recognize them.

2. Send requests to any route. Kong Gateway now rejects requests, because the global plugin requires authentication for all of them.

    curl -si http://kong.example/lemon --resolve kong.example:80:$PROXY_IP
   

   The results should look like this:

    HTTP/1.1 401 Unauthorized
    Date: Fri, 09 Dec 2022 20:10:11 GMT
    Content-Type: application/json; charset=utf-8
    Connection: keep-alive
    WWW-Authenticate: Key realm="kong"
    Content-Length: 45
    x-added-service:  demo
    X-Kong-Response-Latency: 0
    Server: kong/3.0.1
       
    {
      "message":"No API key found in request"
    }
   

   Note that the earlier header plugins are still applied. Plugins that affect responses can modify both proxied responses and responses generated by Kong Gateway.

3. Configure a credential Secret.

    kubectl create secret generic consumer-1-key-auth \
      --from-literal=kongCredType=key-auth  \
      --from-literal=key=consumer-1
   

   The results should look like this:

    secret/consumer-1-key-auth created
   

4. Configure a KongConsumer resource that uses the Secret.

   echo "apiVersion: configuration.konghq.com/v1
   kind: KongConsumer
   metadata:
    name: consumer-1
    annotations:
      kubernetes.io/ingress.class: kong
   username: consumer-1
   credentials:
   - consumer-1-key-auth
   " | kubectl apply -f -
   

   The results should look like this:

    kongconsumer.configuration.konghq.com/consumer-1 created
   

5. Test the global plugin by including the key that now satisfies the authentication requirement enforced by the global plugin.

    curl -sI http://kong.example/lemon --resolve kong.example:80:$PROXY_IP -H 'apikey: consumer-1'
   

   The results should look like this:

    HTTP/1.1 200 OK
    Content-Type: text/html; charset=utf-8
    Content-Length: 9593
    Connection: keep-alive
    Server: gunicorn/19.9.0
    Access-Control-Allow-Origin: *
    Access-Control-Allow-Credentials: true
    x-added-service: demo
    X-Kong-Upstream-Latency: 2
    X-Kong-Proxy-Latency: 1
    Via: kong/3.1.1
   

Configure a plugins for consumers and multiple resources

Plugins can match requests made by a consumer and match requests that meet multiple criteria, such as requests made by a consumer for a specific route.

1. Create a two KongPlugin resources add-header-consumer and add-header-multi that adds a response header x-added-consumer: demo and x-added-multi: demo respectively.

   echo '
   ---
   apiVersion: configuration.konghq.com/v1
   kind: KongPlugin
   metadata:
    name: add-header-consumer
    annotations:
        kubernetes.io/ingress.class: kong
   config:
    add:
      headers:
      - "x-added-consumer: demo"
   plugin: response-transformer
   ---
   apiVersion: configuration.konghq.com/v1
   kind: KongPlugin
   metadata:
    name: add-header-multi
    annotations:
       kubernetes.io/ingress.class: kong
   config:
    add:
      headers:
      - "x-added-multi: demo"
   plugin: response-transformer
   ' | kubectl apply -f -
   

    The results should look like this:
    ```text
    kongplugin.configuration.konghq.com/add-header-consumer created
    kongplugin.configuration.konghq.com/add-header-multi created
   

2. Associate a plugin with a consumer. Similar to the other resources, consumers can use the konghq.com/plugins annotation to associate a plugin.

    kubectl annotate kongconsumer consumer-1 konghq.com/plugins=add-header-consumer
   

   The results should look like this:

    kongconsumer.configuration.konghq.com/consumer-1 annotated
   

3. Verify by sending requests as consumer-1. The response now includes the x-added-consumer: demo header, because consumer plugins take precedence over both route and service plugins.

    curl -si http://kong.example/lemon --resolve kong.example:80:$PROXY_IP -H 'apikey: consumer-1' | grep x-added
   

   The results should look like this:

    x-added-consumer: demo
   

Associate a plugin with a consumer and route

Plugins can be associated with more than one resource. Although routing and Service configuration is implicitly linked (a routing rule cannot proxy to multiple Services), consumers are not. Assigning plugins to multiple resources allows a consumer to use different plugin configuration depending on which route they hit.

1. Add the add-header-multi plugin to a route.

   Ingress

   Gateway APIs

   kubectl annotate ingress lemon konghq.com/plugins=add-header-multi

   kubectl annotate httproute lemon konghq.com/plugins=add-header-multi

   The results should look like this:

   Ingress

   Gateway APIs

   ingress.networking.k8s.io/lemon annotated

   httproute.gateway.networking.k8s.io/lemon annotated

2. Update the consumer configuration to include both plugins.

    kubectl annotate kongconsumer consumer-1 konghq.com/plugins=add-header-consumer,add-header-multi --overwrite
   

   The results should look like this:

    kongconsumer.configuration.konghq.com/consumer-1 annotated
   

3. Send requests with the consumer credentials. The header returned now depend on which route the consumer uses.

   echo "lemon\!"; curl -si http://kong.example/lemon --resolve kong.example:80:$PROXY_IP -H 'apikey: consumer-1' | grep x-added
   echo "lime\!"; curl -si http://kong.example/lime --resolve kong.example:80:$PROXY_IP -H 'apikey: consumer-1' | grep x-added
   

   The results should look like this:

   lemon!
   x-added-multi: demo
   lime!
   x-added-consumer: demo
   

4. Send a request to the lemon route without the consumer credentials and it does not activate the multi-resource plugin, and instead falls back to the Service plugin. When plugins are associated with multiple resources, requests must match all of them.

   curl -si http://kong.example/lemon --resolve kong.example:80:$PROXY_IP | grep x-added
   

   The results should look like this:

   x-added-service:  demo
   

   More specific plugins (for example, a route and consumer, versus just a consumer or just a route) always take precedence over less specific plugins.

Next steps

There’s a lot more you can do with Kong plugins. Check the Plugin Hub to see all of the available plugins and how to use them.

Next, you might want to learn more about Ingress with the KongIngress resource guide.