Controller

class RequestsController < ApplicationController
  skip_before_action :verify_authenticity_token
  before_action :parse_xml

  def ping
    @response_tag = "OTA_PingRS"
  rescue => e
      log_error(e)
      @error = e
      render template: 'requests/error'
  end

  private

  def log_error(e)
    Rails.logger.error e.message
    Rails.logger.error e.backtrace.join("\n")
  end


  def parse_xml
    @msg = Nori.new.parse(request.body.read)
  end

end

Routes

Rails.application.routes.draw do
  post 'ping' => 'requests#ping'
end

View

xml.instruct!
xml.tag!(@response_tag) {
  xml.Success
  xml.EchoData @msg["OTA_PingRQ"]["EchoData"]
}