Understanding the Plug.Builder module

To add a similar plug pipeline to our controller, we will need to keep track of all the plug/3 calls in the controller and apply those plugs in the correct order whenever the controller receives a request. This sounds like a lot of work to do from scratch, but fortunately, the Plug package provides a module that could help – the Plug.Builder module.

The Plug.Builder module can be used to define a pipeline of plugs that are executed one after the other. It defines a plug/2 macro, which is the main interface to build a pipeline by adding a plug to the list of already registered plugs. The plugs in the pipeline are executed in the order of their definition, and the connection returned by the final plug is then passed along to the main plug call.

Here’s an example of this:

defmodule ExamplePlugPipeline do
  use Plug.Builder
  plug :plug1
  plug :plug2
  def plug1(conn, _opts) do
 ...