Kong Plugins as Microservices: Writing a Single-Plugin Server for Kong in Go

Many developers and DevOps engineers have been deploying Kong Gateway in front of their microservices-based applications. While the extensive library of built-in plugins can add a lot of flexibility and power to your deployments, you might encounter the occasional use case where you need a custom plugin that’s just not found in the library.

Fortunately, you can use Go to create and run plugins for Kong Gateway. This post will cover how to get set up for writing Kong plugins. We’ll look at the parts of the request/response lifecycle that you can tap into, and we’ll walk through an example of how to put it all together.

Custom plugins for Kong are achievable using a Go-specific plugin server that uses the sidecar model to load and run a plugin written in Go dynamically. Communication between the plugin and the plugin server is done through a Unix domain socket. Luckily, all of this is made simple through Kong’s Go Plugin Development Kit (PDK).

Why would you write your own plugin?

Ultimately, the ability to write your own Go plugin and integrate it with Kong Gateway provides nearly limitless flexibility during the request and response lifecycle. A classic example would be simple request and response enrichment: Imagine adding or removing headers to influence request routing or incorporating customized request validation or logging requests for auditing. Harnessing Kong Gateway’s power…