class ActionDispatch::RequestId

from multiple pieces of the stack.
The unique request id can be used to trace a request end-to-end and would typically end up being part of log files
header is accepted from the outside world, we sanitize it to a max of 255 chars and alphanumeric and dashes only.
by a firewall, load balancer, or the web server, or, if this header is not available, a random uuid. If the
The unique request id is either based off the X-Request-Id header in the request, which would typically be generated
ActionDispatch::Request#uuid) and sends the same id to the client via the X-Request-Id header.
Makes a unique request id available to the action_dispatch.request_id env variable (which is then accessible through

def call(env) 

def call(env)
  env["action_dispatch.request_id"] = external_request_id(env) || internal_request_id
  @app.call(env).tap { |_status, headers, _body| headers["X-Request-Id"] = env["action_dispatch.request_id"] }
end

def external_request_id(env) 

def external_request_id(env)
  if request_id = env["HTTP_X_REQUEST_ID"].presence
    request_id.gsub(/[^\w\-]/, "").first(255)
  end
end

def initialize(app) 

def initialize(app)
  @app = app
end

def internal_request_id 

def internal_request_id
  SecureRandom.uuid
end