Exit Transformer: Customize the response body and headers - Plugin

Customize the response body and headers

Configure the plugin to replace or add messages and headers in responses.

Prerequisites

untrusted_lua must be set to either on or sandbox in your kong.conf file for this plugin to work.

Set up the plugin

Add this section to your declarative configuration file:

_format_version: "3.0"
plugins:
  - name: exit-transformer
    config:
      functions:
      - return function(status, body, headers) if not body then body = { message = "This
        replaces a formerly empty body" } else body.message = "This replaces a formerly
        non-empty body" end if not headers then headers = { ["X-Message"] = "This adds
        X-Message to an empty set of headers" } else headers["X-Message"] = "This adds
        X-Message to an existing set of headers" end return status, body, headers end

Make the following request:

curl -i -X POST http://localhost:8001/plugins/ \
    --header "Accept: application/json" \
    --header "Content-Type: application/json" \
    --data '
    {
      "name": "exit-transformer",
      "config": {
        "functions": [
          "return function(status, body, headers) if not body then body = { message = \"This replaces a formerly empty body\" } else body.message = \"This replaces a formerly non-empty body\" end if not headers then headers = { [\"X-Message\"] = \"This adds X-Message to an empty set of headers\" } else headers[\"X-Message\"] = \"This adds X-Message to an existing set of headers\" end return status, body, headers end"
        ]
      }
    }
    '

Make the following request:

curl -X POST https://{region}.api.konghq.com/v2/control-planes/{controlPlaneId}/core-entities/plugins/ \
    --header "accept: application/json" \
    --header "Content-Type: application/json" \
    --header "Authorization: Bearer $KONNECT_TOKEN" \
    --data '
    {
      "name": "exit-transformer",
      "config": {
        "functions": [
          "return function(status, body, headers) if not body then body = { message = \"This replaces a formerly empty body\" } else body.message = \"This replaces a formerly non-empty body\" end if not headers then headers = { [\"X-Message\"] = \"This adds X-Message to an empty set of headers\" } else headers[\"X-Message\"] = \"This adds X-Message to an existing set of headers\" end return status, body, headers end"
        ]
      }
    }
    '

Make sure to replace the following placeholders with your own values:

region: Geographic region where your Kong Konnect is hosted and operates.
controlPlaneId: The id of the control plane.
KONNECT_TOKEN: Your Personal Access Token (PAT) associated with your Konnect account.

See the Konnect API reference to learn about region-specific URLs and personal access tokens.

echo "
apiVersion: configuration.konghq.com/v1
kind: KongClusterPlugin
metadata:
  name: exit-transformer
  namespace: kong
  annotations:
    kubernetes.io/ingress.class: kong
  labels:
    global: 'true'
config:
  functions:
  - return function(status, body, headers) if not body then body = { message = 'This
    replaces a formerly empty body' } else body.message = 'This replaces a formerly
    non-empty body' end if not headers then headers = { ['X-Message'] = 'This adds
    X-Message to an empty set of headers' } else headers['X-Message'] = 'This adds
    X-Message to an existing set of headers' end return status, body, headers end
plugin: exit-transformer
" | kubectl apply -f -

Prerequisite: Configure your Personal Access Token

terraform {
  required_providers {
    konnect = {
      source  = "kong/konnect"
    }
  }
}

provider "konnect" {
  personal_access_token = "$KONNECT_TOKEN"
  server_url            = "https://us.api.konghq.com/"
}

Add the following to your Terraform configuration to create a Konnect Gateway Plugin:

resource "konnect_gateway_plugin_exit_transformer" "my_exit_transformer" {
  enabled = true

  config = {
    functions = ["return function(status, body, headers) if not body then body = { message = \"This replaces a formerly empty body\" } else body.message = \"This replaces a formerly non-empty body\" end if not headers then headers = { [\"X-Message\"] = \"This adds X-Message to an empty set of headers\" } else headers[\"X-Message\"] = \"This adds X-Message to an existing set of headers\" end return status, body, headers end"]
  }

  control_plane_id = konnect_gateway_control_plane.my_konnect_cp.id
}

Add this section to your declarative configuration file:

_format_version: "3.0"
plugins:
  - name: exit-transformer
    service: serviceName|Id
    config:
      functions:
      - return function(status, body, headers) if not body then body = { message = "This
        replaces a formerly empty body" } else body.message = "This replaces a formerly
        non-empty body" end if not headers then headers = { ["X-Message"] = "This adds
        X-Message to an empty set of headers" } else headers["X-Message"] = "This adds
        X-Message to an existing set of headers" end return status, body, headers end

Make sure to replace the following placeholders with your own values:

serviceName|Id: The id or name of the service the plugin configuration will target.

Make the following request:

curl -i -X POST http://localhost:8001/services/{serviceName|Id}/plugins/ \
    --header "Accept: application/json" \
    --header "Content-Type: application/json" \
    --data '
    {
      "name": "exit-transformer",
      "config": {
        "functions": [
          "return function(status, body, headers) if not body then body = { message = \"This replaces a formerly empty body\" } else body.message = \"This replaces a formerly non-empty body\" end if not headers then headers = { [\"X-Message\"] = \"This adds X-Message to an empty set of headers\" } else headers[\"X-Message\"] = \"This adds X-Message to an existing set of headers\" end return status, body, headers end"
        ]
      }
    }
    '

Make sure to replace the following placeholders with your own values:

serviceName|Id: The id or name of the service the plugin configuration will target.

Make the following request:

curl -X POST https://{region}.api.konghq.com/v2/control-planes/{controlPlaneId}/core-entities/services/{serviceId}/plugins/ \
    --header "accept: application/json" \
    --header "Content-Type: application/json" \
    --header "Authorization: Bearer $KONNECT_TOKEN" \
    --data '
    {
      "name": "exit-transformer",
      "config": {
        "functions": [
          "return function(status, body, headers) if not body then body = { message = \"This replaces a formerly empty body\" } else body.message = \"This replaces a formerly non-empty body\" end if not headers then headers = { [\"X-Message\"] = \"This adds X-Message to an empty set of headers\" } else headers[\"X-Message\"] = \"This adds X-Message to an existing set of headers\" end return status, body, headers end"
        ]
      }
    }
    '

Make sure to replace the following placeholders with your own values:

region: Geographic region where your Kong Konnect is hosted and operates.
controlPlaneId: The id of the control plane.
KONNECT_TOKEN: Your Personal Access Token (PAT) associated with your Konnect account.
serviceId: The id of the service the plugin configuration will target.

See the Konnect API reference to learn about region-specific URLs and personal access tokens.

echo "
apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: exit-transformer
  namespace: kong
  annotations:
    kubernetes.io/ingress.class: kong
config:
  functions:
  - return function(status, body, headers) if not body then body = { message = 'This
    replaces a formerly empty body' } else body.message = 'This replaces a formerly
    non-empty body' end if not headers then headers = { ['X-Message'] = 'This adds
    X-Message to an empty set of headers' } else headers['X-Message'] = 'This adds
    X-Message to an existing set of headers' end return status, body, headers end
plugin: exit-transformer
" | kubectl apply -f -

Next, apply the KongPlugin resource by annotating the service resource:

kubectl annotate -n kong service SERVICE_NAME konghq.com/plugins=exit-transformer

Prerequisite: Configure your Personal Access Token

terraform {
  required_providers {
    konnect = {
      source  = "kong/konnect"
    }
  }
}

provider "konnect" {
  personal_access_token = "$KONNECT_TOKEN"
  server_url            = "https://us.api.konghq.com/"
}

Add the following to your Terraform configuration to create a Konnect Gateway Plugin:

resource "konnect_gateway_plugin_exit_transformer" "my_exit_transformer" {
  enabled = true

  config = {
    functions = ["return function(status, body, headers) if not body then body = { message = \"This replaces a formerly empty body\" } else body.message = \"This replaces a formerly non-empty body\" end if not headers then headers = { [\"X-Message\"] = \"This adds X-Message to an empty set of headers\" } else headers[\"X-Message\"] = \"This adds X-Message to an existing set of headers\" end return status, body, headers end"]
  }

  control_plane_id = konnect_gateway_control_plane.my_konnect_cp.id
  service = {
    id = konnect_gateway_service.my_service.id
  }
}

Add this section to your declarative configuration file:

_format_version: "3.0"
plugins:
  - name: exit-transformer
    route: routeName|Id
    config:
      functions:
      - return function(status, body, headers) if not body then body = { message = "This
        replaces a formerly empty body" } else body.message = "This replaces a formerly
        non-empty body" end if not headers then headers = { ["X-Message"] = "This adds
        X-Message to an empty set of headers" } else headers["X-Message"] = "This adds
        X-Message to an existing set of headers" end return status, body, headers end

Make sure to replace the following placeholders with your own values:

routeName|Id: The id or name of the route the plugin configuration will target.

Make the following request:

curl -i -X POST http://localhost:8001/routes/{routeName|Id}/plugins/ \
    --header "Accept: application/json" \
    --header "Content-Type: application/json" \
    --data '
    {
      "name": "exit-transformer",
      "config": {
        "functions": [
          "return function(status, body, headers) if not body then body = { message = \"This replaces a formerly empty body\" } else body.message = \"This replaces a formerly non-empty body\" end if not headers then headers = { [\"X-Message\"] = \"This adds X-Message to an empty set of headers\" } else headers[\"X-Message\"] = \"This adds X-Message to an existing set of headers\" end return status, body, headers end"
        ]
      }
    }
    '

Make sure to replace the following placeholders with your own values:

routeName|Id: The id or name of the route the plugin configuration will target.

Make the following request:

curl -X POST https://{region}.api.konghq.com/v2/control-planes/{controlPlaneId}/core-entities/routes/{routeId}/plugins/ \
    --header "accept: application/json" \
    --header "Content-Type: application/json" \
    --header "Authorization: Bearer $KONNECT_TOKEN" \
    --data '
    {
      "name": "exit-transformer",
      "config": {
        "functions": [
          "return function(status, body, headers) if not body then body = { message = \"This replaces a formerly empty body\" } else body.message = \"This replaces a formerly non-empty body\" end if not headers then headers = { [\"X-Message\"] = \"This adds X-Message to an empty set of headers\" } else headers[\"X-Message\"] = \"This adds X-Message to an existing set of headers\" end return status, body, headers end"
        ]
      }
    }
    '

Make sure to replace the following placeholders with your own values:

region: Geographic region where your Kong Konnect is hosted and operates.
controlPlaneId: The id of the control plane.
KONNECT_TOKEN: Your Personal Access Token (PAT) associated with your Konnect account.
routeId: The id of the route the plugin configuration will target.

See the Konnect API reference to learn about region-specific URLs and personal access tokens.

echo "
apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: exit-transformer
  namespace: kong
  annotations:
    kubernetes.io/ingress.class: kong
config:
  functions:
  - return function(status, body, headers) if not body then body = { message = 'This
    replaces a formerly empty body' } else body.message = 'This replaces a formerly
    non-empty body' end if not headers then headers = { ['X-Message'] = 'This adds
    X-Message to an empty set of headers' } else headers['X-Message'] = 'This adds
    X-Message to an existing set of headers' end return status, body, headers end
plugin: exit-transformer
" | kubectl apply -f -

Next, apply the KongPlugin resource by annotating the httproute or ingress resource:

kubectl annotate -n kong httproute  konghq.com/plugins=exit-transformer

kubectl annotate -n kong ingress  konghq.com/plugins=exit-transformer

Prerequisite: Configure your Personal Access Token

terraform {
  required_providers {
    konnect = {
      source  = "kong/konnect"
    }
  }
}

provider "konnect" {
  personal_access_token = "$KONNECT_TOKEN"
  server_url            = "https://us.api.konghq.com/"
}

Add the following to your Terraform configuration to create a Konnect Gateway Plugin:

resource "konnect_gateway_plugin_exit_transformer" "my_exit_transformer" {
  enabled = true

  config = {
    functions = ["return function(status, body, headers) if not body then body = { message = \"This replaces a formerly empty body\" } else body.message = \"This replaces a formerly non-empty body\" end if not headers then headers = { [\"X-Message\"] = \"This adds X-Message to an empty set of headers\" } else headers[\"X-Message\"] = \"This adds X-Message to an existing set of headers\" end return status, body, headers end"]
  }

  control_plane_id = konnect_gateway_control_plane.my_konnect_cp.id
  route = {
    id = konnect_gateway_route.my_route.id
  }
}

Add this section to your declarative configuration file:

_format_version: "3.0"
plugins:
  - name: exit-transformer
    consumer: consumerName|Id
    config:
      functions:
      - return function(status, body, headers) if not body then body = { message = "This
        replaces a formerly empty body" } else body.message = "This replaces a formerly
        non-empty body" end if not headers then headers = { ["X-Message"] = "This adds
        X-Message to an empty set of headers" } else headers["X-Message"] = "This adds
        X-Message to an existing set of headers" end return status, body, headers end

Make sure to replace the following placeholders with your own values:

consumerName|Id: The id or name of the consumer the plugin configuration will target.

Make the following request:

curl -i -X POST http://localhost:8001/consumers/{consumerName|Id}/plugins/ \
    --header "Accept: application/json" \
    --header "Content-Type: application/json" \
    --data '
    {
      "name": "exit-transformer",
      "config": {
        "functions": [
          "return function(status, body, headers) if not body then body = { message = \"This replaces a formerly empty body\" } else body.message = \"This replaces a formerly non-empty body\" end if not headers then headers = { [\"X-Message\"] = \"This adds X-Message to an empty set of headers\" } else headers[\"X-Message\"] = \"This adds X-Message to an existing set of headers\" end return status, body, headers end"
        ]
      }
    }
    '

Make sure to replace the following placeholders with your own values:

consumerName|Id: The id or name of the consumer the plugin configuration will target.

Make the following request:

curl -X POST https://{region}.api.konghq.com/v2/control-planes/{controlPlaneId}/core-entities/consumers/{consumerId}/plugins/ \
    --header "accept: application/json" \
    --header "Content-Type: application/json" \
    --header "Authorization: Bearer $KONNECT_TOKEN" \
    --data '
    {
      "name": "exit-transformer",
      "config": {
        "functions": [
          "return function(status, body, headers) if not body then body = { message = \"This replaces a formerly empty body\" } else body.message = \"This replaces a formerly non-empty body\" end if not headers then headers = { [\"X-Message\"] = \"This adds X-Message to an empty set of headers\" } else headers[\"X-Message\"] = \"This adds X-Message to an existing set of headers\" end return status, body, headers end"
        ]
      }
    }
    '

Make sure to replace the following placeholders with your own values:

region: Geographic region where your Kong Konnect is hosted and operates.
controlPlaneId: The id of the control plane.
KONNECT_TOKEN: Your Personal Access Token (PAT) associated with your Konnect account.
consumerId: The id of the consumer the plugin configuration will target.

See the Konnect API reference to learn about region-specific URLs and personal access tokens.

echo "
apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: exit-transformer
  namespace: kong
  annotations:
    kubernetes.io/ingress.class: kong
config:
  functions:
  - return function(status, body, headers) if not body then body = { message = 'This
    replaces a formerly empty body' } else body.message = 'This replaces a formerly
    non-empty body' end if not headers then headers = { ['X-Message'] = 'This adds
    X-Message to an empty set of headers' } else headers['X-Message'] = 'This adds
    X-Message to an existing set of headers' end return status, body, headers end
plugin: exit-transformer
" | kubectl apply -f -

Next, apply the KongPlugin resource by annotating the KongConsumer resource:

kubectl annotate -n kong  CONSUMER_NAME konghq.com/plugins=exit-transformer

Prerequisite: Configure your Personal Access Token

terraform {
  required_providers {
    konnect = {
      source  = "kong/konnect"
    }
  }
}

provider "konnect" {
  personal_access_token = "$KONNECT_TOKEN"
  server_url            = "https://us.api.konghq.com/"
}

Add the following to your Terraform configuration to create a Konnect Gateway Plugin:

resource "konnect_gateway_plugin_exit_transformer" "my_exit_transformer" {
  enabled = true

  config = {
    functions = ["return function(status, body, headers) if not body then body = { message = \"This replaces a formerly empty body\" } else body.message = \"This replaces a formerly non-empty body\" end if not headers then headers = { [\"X-Message\"] = \"This adds X-Message to an empty set of headers\" } else headers[\"X-Message\"] = \"This adds X-Message to an existing set of headers\" end return status, body, headers end"]
  }

  control_plane_id = konnect_gateway_control_plane.my_konnect_cp.id
  consumer = {
    id = konnect_gateway_consumer.my_consumer.id
  }
}

Exit Transformer

Customize the response body and headers

Prerequisites

Set up the plugin

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