gistfile1.rb

now = Time.now.to_f
milliseconds = (now * 1_000).to_i
microseconds = (now * 1_000_000).to_i

# Wait time doesn't seem to represent queue time like we want to capture
env.delete("HTTP_X_HEROKU_QUEUE_WAIT_TIME")

env["HTTP_X_MIDDLEWARE_START"] = "t=#{microseconds}"

if env["HTTP_X_REQUEST_START"]
  # HTTP_X_REQUEST_START is expected by New Relic to have a t= leading
  # but currently doesn't, so it can just get to_i applied.
  request_start_milliseconds = env["HTTP_X_REQUEST_START"].to_i
  request_start_microseconds = request_start_milliseconds * 1_000

  queue_time_milliseconds = milliseconds - request_start_milliseconds
  queue_time_microseconds = microseconds - request_start_microseconds

  env["HTTP_X_QUEUE_TIME"] = "t=#{queue_time_microseconds}"
end