class `ActionDispatch::RequestId`

Action Dispatch RequestId

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.

Public class methods

`new(app, header:)`

Source code GitHub

# File actionpack/lib/action_dispatch/middleware/request_id.rb, line 25
def initialize(app, header:)
  @app = app
  @header = header
  @env_header = "HTTP_#{header.upcase.tr("-", "_")}"
end

Public instance methods

`call(env)`

Source code GitHub

# File actionpack/lib/action_dispatch/middleware/request_id.rb, line 31
def call(env)
  req = ActionDispatch::Request.new env
  req.request_id = make_request_id(req.get_header(@env_header))
  @app.call(env).tap { |_status, headers, _body| headers[@header] = req.request_id }
end

Definition files

actionpack/lib/action_dispatch/middleware/request_id.rb

class ActionDispatch::RequestId