Health checks can be used for liveness or readiness probes.

Health checks are separated from the functionality of the application, because of that, it's better to minimize the impact on application.

They should meet the following requirements:

1. run as light as possible.
2. not generate logs.

Usage

The basic idea is adding it to the top of plugs.

Add it to the top of endpoint.ex in Phoenix:

defmodule HelloWeb.Endpoint do
  use Phoenix.Endpoint, otp_app: :hello

  # Put the health check here, before anything else
  plug Retro.Phoenix.Plug.HealthCheck
end

References

• Health checks for Plug and Phoenix