Create an Event Hook that can run custom code with Kong Gateway

A lambda Event Hook is an Event Hook that utilizes the lambda handler to pass custom code to an Event Hook. Depending on the source and individual event, that code can execute during various stages of the lifecycle of an event. In this guide, you will create an lambda Event Hook with custom code that logs an error with a specific message every time you create a Consumer.

Create a Lua script to load into the lambda Event Hook.

return function (data, event, source, pid)
local user = data.entity.username
error("Event Hook on consumer " .. user .. "")
end

Create a lambda Event Hook on the consumers event, with the crud source by creating a POST request to the Admin API and passing the code in the request body as an array of strings.

curl -i -X POST http://localhost:8001/event-hooks/ \
    --header "Accept: application/json" \
    --header "Content-Type: application/json" \
    --data '
    {
      "source": "crud",
      "event": "consumers",
      "handler": "lambda",
      "config": {
        "functions": [
          "return function (data, event, source, pid) local user = data.entity.username error(\"Event Hook on consumer \" .. user .. \"\") end"
        ]
      }
    }
    '

Important: Before you can use Event Hooks for the first time, Kong Gateway needs to be reloaded.

Using the Admin API create a new Consumer:

curl -i -X POST http://localhost:8001/consumers/ \
    --header "Accept: application/json" \
    --header "Content-Type: application/json" \
    --data '
    {
      "username": "my-consumer"
    }
    '

Review the logs at /usr/local/kong/logs/error.log for an update about the creation of this Consumer. The log will look similar to this:

2024/12/16 21:52:54 [error] 114#0: *153047 [kong] event_hooks.lua:190 [string "return function (data, event, source, pid)..."]:3: Event Hook on consumer my-consumer, context: ngx.timer, client: 172.19.0.1, server: 0.0.0.0:8001

In the error logs, you will see the Event Hook and the error log that resulted from error("Event Hook on consumer " .. user .. "").