Add(delta int) error

	// Done decrements the WaitGroup counter.
	Done()
}

// WithWaitGroup adds all non long-running requests to wait group, which is used for graceful shutdown.
func WithWaitGroup(handler http.Handler, longRunning apirequest.LongRunningRequestCheck, wg RequestWaitGroup) http.Handler {
	// NOTE: both WithWaitGroup and WithRetryAfter must use the same exact isRequestExemptFunc 'isRequestExemptFromRetryAfter,

//
// TODO: is there a way to merge WithWaitGroup and this filter?
func WithRetryAfter(handler http.Handler, shutdownDelayDurationElapsedCh <-chan struct{}) http.Handler {
	shutdownRetryAfterParams := &retryAfterParams{
		TearDownConnection: true,
		Message:            "The apiserver is shutting down, please try again later.",
	}

			if test.safeWaitGroupIsWaiting {
				// mark the safe wait group as waiting, it's a blocking call
				// but since the WaitGroup counter is zero it should not block
				safeWG.Wait()
			}

			wrapped := WithWaitGroup(handler, func(*http.Request, *apirequest.RequestInfo) bool {
				return false
			}, safeWG)
			wrapped = WithRetryAfter(wrapped, test.shutdownDelayDurationElapsedFn())

	config, _ := setUp(t)

	var graceShutdown bool
	wg := sync.WaitGroup{}
	wg.Add(1)

	config.BuildHandlerChainFunc = func(apiHandler http.Handler, c *Config) http.Handler {
		handler := genericfilters.WithWaitGroup(apiHandler, c.LongRunningFunc, c.NonLongRunningRequestWaitGroup)
		handler = genericapifilters.WithRequestInfo(handler, c.RequestInfoResolver)
		return handler
	}

		}
		return true, nil
	}); err != nil {
		t.Errorf("Expected no error, but got: %v", err)
	}

	// TODO: our original intention was for any incoming request to receive a 503
	// via the WithWaitGroup filter, but, at this point, any incoming requests
	// will get a 'connection refused' error since the net/http server has
	// stopped listening.

	handler = genericapifilters.WithRequestDeadline(handler, c.AuditBackend, c.AuditPolicyRuleEvaluator,
		c.LongRunningFunc, c.Serializer, c.RequestTimeout)
	handler = genericfilters.WithWaitGroup(handler, c.LongRunningFunc, c.NonLongRunningRequestWaitGroup)
	if c.ShutdownWatchTerminationGracePeriod > 0 {
		handler = genericfilters.WithWatchTerminationDuringShutdown(handler, c.lifecycleSignals, c.WatchRequestWaitGroup)

		// once NonLongRunningRequestWaitGroup.Wait is invoked, the apiserver is
		// expected to reject any incoming request with a {503, Retry-After}
		// response via the WithWaitGroup filter. On the contrary, we observe
		// that incoming request(s) get a 'connection refused' error, this is
		// because, at this point, we have called 'Server.Shutdown' and

		handlerFunc = metrics.InstrumentHandlerFunc(verb, requestInfo.APIGroup, requestInfo.APIVersion, resource, subresource, scope, metrics.APIServerComponent, deprecated, "", handlerFunc)
		handler := genericfilters.WithWaitGroup(handlerFunc, longRunningFilter, crdInfo.waitGroup)
		handler.ServeHTTP(w, req)
		return
	}
}