How Statifier.Send.BasicHTTP POSTs a message (ADR-0075 decision 6): one callback that sends a body with headers to a URL and answers the status code, or an error when no status came back.

The default is Statifier.Send.BasicHTTP.Transport.Httpc, on OTP's :httpc, which this package always compiles and adds no dependency for. A host injects any other module through the registration's :transport option. An adapter makes one attempt: retrying is not the transport's job, and a status outside 2xx is answered as {:ok, status}, not as an error, so the processor reports it as a miss.

A host that uses req writes an adapter of its own:

defmodule MyApp.ReqTransport do
  @behaviour Statifier.Send.BasicHTTP.Transport

  @impl true
  def post(url, headers, body) do
    case Req.post(url, headers: headers, body: body, retry: false) do
      {:ok, %Req.Response{status: status}} -> {:ok, status}
      {:error, exception} -> {:error, exception}
    end
  end
end