gistfile1.rb

def load_customer
  if customer_id = session[:customer_id]
    @customer = Customer.find_by_id(session[:customer_id])
  end
  # in reality e.g. a redis exception thrown from the driver
  # could be raised from circuit breaker or semian as well (see later)
rescue Sessions::DataStoreUnavailable
  flash[:notice] = 'Customer sign in is currently unavailable'
  @customer = nil
end