dynamic_environment_switching_middleware

🔄 Dynamic Environment Switching via Middleware

For multi‑tenant or on‑demand sandbox setups, you can intercept each request and swap Rails.env dynamically, letting you load per‑tenant configs or credentials before the app bootstraps deeper layers.

Create a middleware at lib/middleware/env_switcher.rb:

class EnvSwitcher
  def initialize(app)
    @app = app
  end

  def call(env)
    tenant = extract_tenant(env)
    original_env = Rails.env

    # e.g. set to "tenant_123"
    Rails.instance_variable_set(:@_env, ActiveSupport::StringInquirer.new(tenant))

    @app.call(env)
  ensure
    # restore original
    Rails.instance_variable_set(:@_env, ActiveSupport::StringInquirer.new(original_env))
  end

  private

  def extract_tenant(env)
    # parse subdomain or header
    ActionDispatch::Request.new(env).subdomains.first || Rails.env
  end
end

Then insert it early in config/application.rb:

module MyApp
  class Application < Rails::Application
    config.load_defaults 7.0
    config.middleware.insert_before Rails::Rack::Logger, "EnvSwitcher"
  end
end