require "securerandom" require "active_support/core_ext/string/access" module ActionDispatch # Makes a unique request id available to the +action_dispatch.request_id+ env variable (which is then accessible # through ActionDispatch::Request#request_id or the alias ActionDispatch::Request#uuid) and sends # the same id to the client via the X-Request-Id header. # # The unique request id is either based on the X-Request-Id header in the request, which would typically be generated # by a firewall, load balancer, or the web server, or, if this header is not available, a random uuid. If the # header is accepted from the outside world, we sanitize it to a max of 255 chars and alphanumeric and dashes only. # # The unique request id can be used to trace a request end-to-end and would typically end up being part of log files # from multiple pieces of the stack. class RequestId X_REQUEST_ID = "X-Request-Id".freeze #:nodoc: def initialize(app) @app = app end def call(env) req = ActionDispatch::Request.new env req.request_id = make_request_id(req.x_request_id) @app.call(env).tap { |_status, headers, _body| headers[X_REQUEST_ID] = req.request_id } end private def make_request_id(request_id) if request_id.presence request_id.gsub(/[^\w\-]/, "".freeze).first(255) else internal_request_id end end def internal_request_id SecureRandom.uuid end end end