failonstatus - A single or comma-separated list of HTTP status codes. If set this will force the worker into error state when the backend returns any status code in the list. Worker recovery behaves the same as other worker errors. Available with Apache HTTP Server 2.2.17 and later.However as soon as the status code is returned for the first time by the backend the proxy sends it back to the client. This behavior should be configurable with for example SilentOnStatus which works just as FailOnStatus but it prevents feedback to be sent back to the client.
As it stands our only resource is to create an ErrorDocument and include some logic to automatically retry again while communicating the user that a recovery from the error is coming soon. For example you could redirect to the domain root after five seconds with Meta Refresh: This is a feature needed to make sure users do not get an error message when an application server is restarting and so unavailable (500) or when it is available but at a point where the application has not been loaded (503).