@Override
        public ContentChannel handleResponse(Response response) {
            if ( tryHasResponded()) throw new IllegalStateException("Response already handled");
            if (getRequestType().isPresent() && response.getRequestType() == null)
                response.setRequestType(getRequestType().get());
            ContentChannel cc = responseHandler.handleResponse(response);
            metricUtil.onHandled(request);
            return cc;
        }
Invoked to write an error response when the worker pool is overloaded.
A subclass may override this method to define a custom response.
container-core/src/main/java/com/yahoo/container/jdisc/ThreadedRequestHandler.java