Request Transformer Advanced

The Request Transformer plugin for Kong Enterprise builds on the Kong version of this plugin with enhanced capabilities to match portions of incoming requests using regular expressions, save those matched strings into variables, and substitute those strings into transformed requests via flexible templates.

Terminology

• plugin: a plugin executing actions inside Kong before or after a request has been proxied to the upstream API.
• Service: the Kong entity representing an external upstream API or microservice.
• Route: the Kong entity representing a way to map downstream requests to upstream services.
• Consumer: the Kong entity representing a developer or machine using the API. When using Kong, a Consumer only communicates with Kong which proxies every call to the said upstream API.
• Credential: a unique string associated with a Consumer, also referred to as an API key.
• upstream service: this refers to your own API/service sitting behind Kong, to which client requests are forwarded.
• API: a legacy entity used to represent your upstream services. Deprecated in favor of Services since CE 0.13.0 and EE 0.32.

Configuration

Enabling the plugin on a Service

With a database

Configure this plugin on a Service by making the following request:

$ curl -X POST http://kong:8001/services/{service}/plugins \
    --data "name=request-transformer-advanced" 

Without a database

Configure this plugin on a Service by adding this section do your declarative configuration file:

plugins:
- name: request-transformer-advanced
  service: {service}
  config: 

In both cases, {service} is the id or name of the Service that this plugin configuration will target.

Enabling the plugin on a Route

With a database

Configure this plugin on a Route with:

$ curl -X POST http://kong:8001/routes/{route}/plugins \
    --data "name=request-transformer-advanced" 

Without a database

Configure this plugin on a Route by adding this section do your declarative configuration file:

plugins:
- name: request-transformer-advanced
  route: {route}
  config: 

In both cases, {route} is the id or name of the Route that this plugin configuration will target.

Enabling the plugin on a Consumer

With a database

You can use the http://localhost:8001/plugins endpoint to enable this plugin on specific Consumers:

$ curl -X POST http://kong:8001/consumers/{consumer}/plugins \
    --data "name=request-transformer-advanced" \
    

Without a database

Configure this plugin on a Consumer by adding this section do your declarative configuration file:

plugins:
- name: request-transformer-advanced
  consumer: {consumer}
  config: 

In both cases, {consumer} is the id or username of the Consumer that this plugin configuration will target.

You can combine consumer_id and service_id

in the same request, to furthermore narrow the scope of the plugin.

Enabling the plugin on an API

If you are using an older version of Kong with the legacy API entity (deprecated in favor of Services since CE 0.13.0 and EE 0.32.), you can configure this plugin on top of such an API by making the following request:

$ curl -X POST http://kong:8001/apis/{api}/plugins \
    --data "name=request-transformer-advanced" 

• api: either id or name of the API that this plugin configuration will target.

Global plugins

• Using a database, all plugins can be configured using the http://kong:8001/plugins/ endpoint.
• Without a database, all plugins can be configured via the plugins: entry on the declarative configuration file.

A plugin which is not associated to any Service, Route or Consumer (or API, if you are using an older version of Kong) is considered "global", and will be run on every request. Read the Plugin Reference and the Plugin Precedence sections for more information.

Parameters

Here's a list of all the parameters which can be used in this plugin's configuration:

Note: if the value contains a , then the comma separated format cannot be used. The array notation must be used instead.

Template as Value

User can use any of the the current request headers, query params, and captured URI named groups as template to populate above supported config fields.

To escape a template, wrap it inside quotes and pass inside another template.
Ex. $(‘$(some_needs_to_escaped)’)

Note: Plugin creates a non mutable table of request headers, querystrings, and captured URIs before transformation. So any update or removal of params used in template does not affect the rendered value of template.

Examples Using Template as Value

Add an API test with uris configured with a named capture group user_id

$ curl -X POST http://localhost:8001/apis \
    --data 'name=test' \
    --data 'upstream_url=http://mockbin.com' \
    --data-urlencode 'uris=/requests/user/(?<user_id>\w+)' \
    --data "strip_uri=false"

Enable the ‘request-transformer-advanced’ plugin to add a new header x-consumer-id and its value is being set with the value sent with header x-user-id or with the default value alice is header is missing.

$ curl -X POST http://localhost:8001/apis/test/plugins \
    --data "name=request-transformer-advanced" \
    --data-urlencode "config.add.headers=x-consumer-id:\$(headers['x-user-id'] or 'alice')" \
    --data "config.remove.headers=x-user-id"

Now send a request without setting header x-user-id

$ curl -i -X GET localhost:8000/requests/user/foo

Plugin will add a new header x-consumer-id with value alice before proxying request upstream. Now try sending request with header x-user-id set

$ curl -i -X GET localhost:8000/requests/user/foo \
  -H "X-User-Id:bob"

This time plugin will add a new header x-consumer-id with value sent along with header x-user-id, i.e.bob

Order of Execution

Plugin performs the response transformation in following order

remove –> replace –> add –> append

Configuration Examples

Add multiple headers by passing each header:value pair separately:

$ curl -X POST http://localhost:8001/apis/mockbin/plugins \
  --data "name=request-transformer-advanced" \
  --data "config.add.headers[1]=h1:v1" \
  --data "config.add.headers[2]=h2:v1"

Add multiple headers by passing comma separated header:value pair:

$ curl -X POST http://localhost:8001/apis/mockbin/plugins \
  --data "name=request-transformer-advanced" \
  --data "config.add.headers=h1:v1,h2:v2"

Add multiple headers passing config as JSON body:

$ curl -X POST http://localhost:8001/apis/mockbin/plugins \
  --header 'content-type: application/json' \
  --data '{"name": "request-transformer-advanced", "config": {"add": {"headers": ["h1:v2", "h2:v1"]}}}'

Add a querystring and a header:

$ curl -X POST http://localhost:8001/apis/mockbin/plugins \
  --data "name=request-transformer-advanced" \
  --data "config.add.querystring=q1:v2,q2=v1" \
  --data "config.add.headers=h1:v1"

Append multiple headers and remove a body parameter:

$ curl -X POST http://localhost:8001/apis/mockbin/plugins \
  --data "name=request-transformer-advanced" \
  --data "config.add.headers=h1:v2,h2:v1" \
  --data "config.remove.body=p1" \

Add multiple headers and querystring parameters if not already set:

$ curl -X POST http://localhost:8001/apis/mockbin/plugins \
  --data "name=request-transformer-advanced" \
  --data "config.add.headers=h1:v1,h2:v1" \
  --data "config.add.querystring=q1:v2,q2:v1" \