How to Control Maintenance Mode (Render 503) by Env Vars with Rails

application_controller.rb

# app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
  before_action :render_503_except_for_whitelisted_ips, if: :maintenance_mode?

  def maintenance_mode?
    ENV["MAINTENANCE_MODE"] == "true"
  end

  def render_503_except_for_whitelisted_ips
    ips_in_whitelist = (ENV["ALLOWED_IPS"] || "").split(",")
    return if ips_in_whitelist.include?(request.remote_ip)

    render(
      file: Rails.public_path.join("503.html"),
      content_type: "text/html",
      layout: false,
      status: :service_unavailable,
    )
  end
end

Control Maintenance Mode (Render 503) by Env Vars with Rails.md

Environment variables

Key	VALUE
MAINTENANCE_MODE	When "true", your Rails app runs as maintenance mode
ALLOWED_IPS	Set IP addresses you allow to access your Rails app when maintenance mode

Example

$ MAINTENANCE_MODE=true ALLOWED_IPS=192.168.145.2,192.168.145.3 bin/rails s -b 0.0.0.0