Merge pull request kubernetes#105827 from benluddy/automated-cherry-p…

…ick-of-#105511-upstream-release-1.22

Automated cherry pick of kubernetes#105511: Free APF seats for watches handled by an aggregated

staging/src/k8s.io/apiserver/pkg/util/flowcontrol/apf_context.go

@@ -52,6 +52,17 @@ func WatchInitialized(ctx context.Context) {
 	}
 }
 
+// RequestDelegated informs the priority and fairness dispatcher that
+// a given request has been delegated to an aggregated API
+// server. No-op when priority and fairness is disabled.
+func RequestDelegated(ctx context.Context) {
+	// The watch initialization signal doesn't traverse request
+	// boundaries, so we generously fire it as soon as we know
+	// that the request won't be serviced locally. Safe to call
+	// for non-watch requests.
+	WatchInitialized(ctx)
+}
+
 // InitializationSignal is an interface that allows sending and handling
 // initialization signals.
 type InitializationSignal interface {

staging/src/k8s.io/kube-aggregator/pkg/apiserver/handler_proxy.go

@@ -35,6 +35,7 @@ import (
 	genericfeatures "k8s.io/apiserver/pkg/features"
 	"k8s.io/apiserver/pkg/server/egressselector"
 	utilfeature "k8s.io/apiserver/pkg/util/feature"
+	utilflowcontrol "k8s.io/apiserver/pkg/util/flowcontrol"
 	"k8s.io/apiserver/pkg/util/x509metrics"
 	restclient "k8s.io/client-go/rest"
 	"k8s.io/client-go/transport"
@@ -175,6 +176,7 @@ func (r *proxyHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	handler := proxy.NewUpgradeAwareHandler(location, proxyRoundTripper, true, upgrade, &responder{w: w})
 	handler.InterceptRedirects = utilfeature.DefaultFeatureGate.Enabled(genericfeatures.StreamingProxyRedirects)
 	handler.RequireSameHostRedirects = utilfeature.DefaultFeatureGate.Enabled(genericfeatures.ValidateProxyRedirects)
+	utilflowcontrol.RequestDelegated(req.Context())
 	handler.ServeHTTP(w, newReq)
 }
 

staging/src/k8s.io/kube-aggregator/pkg/apiserver/handler_proxy_test.go

@@ -46,6 +46,7 @@ import (
 	"k8s.io/apiserver/pkg/authentication/user"
 	genericapirequest "k8s.io/apiserver/pkg/endpoints/request"
 	"k8s.io/apiserver/pkg/server/egressselector"
+	utilflowcontrol "k8s.io/apiserver/pkg/util/flowcontrol"
 	"k8s.io/component-base/metrics"
 	"k8s.io/component-base/metrics/legacyregistry"
 	apiregistration "k8s.io/kube-aggregator/pkg/apis/apiregistration/v1"
@@ -899,6 +900,135 @@ func TestProxyCertReload(t *testing.T) {
 	}
 }
 
+type fcInitSignal struct {
+	nSignals int32
+}
+
+func (s *fcInitSignal) SignalCount() int {
+	return int(atomic.SwapInt32(&s.nSignals, 0))
+}
+
+func (s *fcInitSignal) Signal() {
+	atomic.AddInt32(&s.nSignals, 1)
+}
+
+func (s *fcInitSignal) Wait() {
+}
+
+type hookedListener struct {
+	l        net.Listener
+	onAccept func()
+}
+
+func (wl *hookedListener) Accept() (net.Conn, error) {
+	wl.onAccept()
+	return wl.l.Accept()
+}
+
+func (wl *hookedListener) Close() error {
+	return wl.l.Close()
+}
+
+func (wl *hookedListener) Addr() net.Addr {
+	return wl.l.Addr()
+}
+
+func TestFlowControlSignal(t *testing.T) {
+	for _, tc := range []struct {
+		Name           string
+		Local          bool
+		Available      bool
+		Request        http.Request
+		SignalExpected bool
+	}{
+		{
+			Name:           "local",
+			Local:          true,
+			SignalExpected: false,
+		},
+		{
+			Name:           "unavailable",
+			Local:          false,
+			Available:      false,
+			SignalExpected: false,
+		},
+		{
+			Name:           "request performed",
+			Local:          false,
+			Available:      true,
+			SignalExpected: true,
+		},
+		{
+			Name:      "upgrade request performed",
+			Local:     false,
+			Available: true,
+			Request: http.Request{
+				Header: http.Header{"Connection": []string{"Upgrade"}},
+			},
+			SignalExpected: true,
+		},
+	} {
+		t.Run(tc.Name, func(t *testing.T) {
+			okh := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.WriteHeader(http.StatusOK)
+			})
+
+			var sig fcInitSignal
+
+			var signalCountOnAccept int32
+			backend := httptest.NewUnstartedServer(okh)
+			backend.Listener = &hookedListener{
+				l: backend.Listener,
+				onAccept: func() {
+					atomic.StoreInt32(&signalCountOnAccept, int32(sig.SignalCount()))
+				},
+			}
+			backend.Start()
+			defer backend.Close()
+
+			p := proxyHandler{
+				localDelegate:   okh,
+				serviceResolver: &mockedRouter{destinationHost: backend.Listener.Addr().String()},
+			}
+
+			server := httptest.NewServer(contextHandler(
+				http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+					p.ServeHTTP(w, r.WithContext(utilflowcontrol.WithInitializationSignal(r.Context(), &sig)))
+				}),
+				&user.DefaultInfo{
+					Name:   "username",
+					Groups: []string{"one", "two"},
+				},
+			))
+			defer server.Close()
+
+			p.handlingInfo.Store(proxyHandlingInfo{
+				local:             tc.Local,
+				serviceAvailable:  tc.Available,
+				proxyRoundTripper: backend.Client().Transport,
+			})
+
+			surl, err := url.Parse(server.URL)
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+
+			req := tc.Request
+			req.URL = surl
+			_, err = server.Client().Do(&req)
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+
+			if fired := (atomic.LoadInt32(&signalCountOnAccept) > 0); tc.SignalExpected && !fired {
+				t.Errorf("flow control signal expected but not fired")
+			} else if fired && !tc.SignalExpected {
+				t.Errorf("flow control signal fired but not expected")
+			}
+		})
+	}
+}
+
 func getCertAndKeyPaths(t *testing.T) (string, string, string) {
 	dir, err := ioutil.TempDir(os.TempDir(), "k8s-test-handler-proxy-cert")
 	if err != nil {