PingPlug, a plug to echo a defined message.

PingPlug can be used in two ways, execute a function or echo a message.

Execute a function

To execute any function you must define a module function that return:

{:ok, String.t()} | {:error, String.t()}

In which,

• :ok will be mapped to HTTP 200, and
• :error will be mapped to HTTP 500

A simple use case is to use it as a liveness probe. For example, configure PingPlug to match a specific path and execute dependency checks.

Examples

Here is an example of returning a value when a request hits /_checks/liveness path.

# endpoint.ex

plug PingPlug, path: ["_checks", "liveness"], return: "alive!"

Here is an example of executing a function to check database connectivity.

First, define a module that sends a query to a database to ensure it is up and running.

# db_check.ex

defmodule DBCheck do
  @behaviour PingPlug

  @impl true
  def check do
    case Ecto.Adapters.SQL.query(Repo, "SELECT 1") do
      {:ok, _result} ->
        {:ok, "ready!"}

      {:error, exception} ->
        {:error, Exception.message(exception)}
    end
  end
end

Then plug it into the readiness endpoint.

# endpoint.ex

plug PingPlug, path: ["_checks", "readiness"], execute: {DBCheck, :check, []}