Custom Plugins

Install a custom plugin in Kong without using a Docker build.

The recommended way to install custom plugins is with Kong Gateway Operator. See Kong custom plugin distribution with KongPluginInstallation for more information.

Create a custom plugin

For details about plugin development for Kong Gateway, see the Plugin Development guide.

Create a directory with plugin code.

If you already have a real plugin, you can skip this step.

 mkdir myheader
 echo 'local MyHeader = {}

 MyHeader.PRIORITY = 1000
 MyHeader.VERSION = "1.0.0"

 function MyHeader:header_filter(conf)
   -- do custom logic here
   kong.response.set_header("myheader", conf.header_value)
 end

 return MyHeader
 ' > myheader/handler.lua

 echo 'return {
   name = "myheader",
   fields = {
     { config = {
         type = "record",
         fields = {
           { header_value = { type = "string", default = "roar", }, },
         },
     }, },
   }
 }
 ' > myheader/schema.lua

The directory should now look like this:

 tree myheader

 myheader
 ├── handler.lua
 └── schema.lua

 0 directories, 2 files

Create a ConfigMap or Secret with the plugin code. If you’re not sure which option is correct, use a ConfigMap.

If you would like to install a plugin which is available as a rock from Luarocks, then you need to download it, unzip it and create a ConfigMap or secret from all the Lua files of the plugin.
ConfigMap

Secret
$ kubectl create configmap kong-plugin-myheader --from-file=myheader -n kong
$ kubectl create secret generic -n kong kong-plugin-myheader --from-file=myheader
The results should look like this:
ConfigMap

Secret
configmap/kong-plugin-myheader created
secret/kong-plugin-myheader created

Deploying custom plugins

Helm

The easiest way to use custom plugins with Kong is via the Helm chart. The chart automatically configures all the environment variables based on the plugins you inject.

Create a values.yaml file with the following contents. Ensure that you add in other configuration values you might need for your installation to be successful.

      ConfigMap
    

      Secret
    
gateway:
  plugins:
    configMaps:
    - name: kong-plugin-myheader
      pluginName: myheader
gateway:
  plugins:
    secrets:
    - name: kong-plugin-myheader
      pluginName: myheader

Install Kong Ingress Controller.

 helm repo add kong https://charts.konghq.com
 helm repo update
 helm install kong kong/ingress -n kong --create-namespace --values values.yaml

Non-Helm

The following examples assume that you have a deployment named proxy-kong. Change this to the name of your deployment as needed.

Modify configuration to update Kong’s Deployment to load the custom plugin.

The following patch is necessary to load the plugin.
- The plugin code is mounted into the pod via volumeMounts and volumes configuration property.
- KONG_PLUGINS environment variable is set to include the custom plugin along with all the plugins that come in Kong by default.
- KONG_LUA_PACKAGE_PATH environment variable directs Kong to look for plugins in the directory where we are mounting them.
If you have multiple plugins, mount multiple ConfigMaps and include the plugin name in the KONG_PLUGINS environment variable.

Note that if your plugin code involves database migration then you need to include the following patch to pod definition of your migration Job as well. This is not a complete definition of the Deployment but a strategic patch which can be applied to an existing Deployment.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: proxy-kong
  namespace: kong
spec:
  template:
    spec:
      containers:
      - name: proxy
        env:
        - name: KONG_PLUGINS
          value: bundled,myheader
        - name: KONG_LUA_PACKAGE_PATH
          value: "/opt/?.lua;;"
        volumeMounts:
        - name: kong-plugin-myheader
          mountPath: /opt/kong/plugins/myheader
      volumes:
      - name: kong-plugin-myheader
        configMap:
          name: kong-plugin-myheader

Using custom plugins

After you have setup Kong with the custom plugin installed, you can use it like any other plugin. Create a KongPlugin custom resource:

echo '
apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: my-custom-plugin
config:
  header_value: "my first plugin"
plugin: myheader
' | kubectl apply -f -

Add the konghq.com/plugins annotation to your Service, Ingress or Gateway API route to instruct Kong to execute the plugin:
```
konghq.com/plugins: my-custom-plugin
```

Plugins in other languages

When deploying custom plugins in other languages, especially Golang, the built binary is larger than the size limit of ConfigMap. In such cases, consider using an init container to pull large binaries from remotes like S3 buckets, or build a custom image that includes plugin runtimes and the plugin itself.

To read more about building a custom image, see use external plugins in container and Kubernetes.