class ActionDispatch::Request

This relies on the Rack variable set by the ActionDispatch::RequestId middleware.
This unique ID is useful for tracing a request from end-to-end as part of logging or debugging.

(which sets the +action_dispatch.request_id+ environment variable).
be generated by a firewall, load balancer, or web server, or by the RequestId middleware
Returns the unique request id, which is based on either the +X-Request-Id+ header that can

def request_id
  get_header ACTION_DISPATCH_REQUEST_ID
end