Merge pull request #120902 from linxiulei/watch_stack

Add handler to run execution in separate goroutine

pkg/features/kube_features.go

@@ -1173,6 +1173,8 @@ var defaultKubernetesFeatureGates = map[featuregate.Feature]featuregate.FeatureS
 
 	genericfeatures.APIServerTracing: {Default: true, PreRelease: featuregate.Beta},
 
+	genericfeatures.APIServingWithRoutine: {Default: true, PreRelease: featuregate.Beta},
+
 	genericfeatures.ConsistentListFromCache: {Default: false, PreRelease: featuregate.Alpha},
 
 	genericfeatures.CustomResourceValidationExpressions: {Default: true, PreRelease: featuregate.GA, LockToDefault: true}, // remove in 1.31

staging/src/k8s.io/apiserver/pkg/endpoints/handlers/get.go

@@ -41,6 +41,7 @@ import (
 	"k8s.io/apiserver/pkg/endpoints/request"
 	"k8s.io/apiserver/pkg/features"
 	"k8s.io/apiserver/pkg/registry/rest"
+	genericfilters "k8s.io/apiserver/pkg/server/filters"
 	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	"k8s.io/component-base/tracing"
 	"k8s.io/klog/v2"
@@ -259,7 +260,7 @@ func ListResource(r rest.Lister, rw rest.Watcher, scope *RequestScope, forceWatc
 			}
 			klog.V(3).InfoS("Starting watch", "path", req.URL.Path, "resourceVersion", opts.ResourceVersion, "labels", opts.LabelSelector, "fields", opts.FieldSelector, "timeout", timeout)
 			ctx, cancel := context.WithTimeout(ctx, timeout)
-			defer cancel()
+			defer func() { cancel() }()
 			watcher, err := rw.Watch(ctx, &opts)
 			if err != nil {
 				scope.err(err, w, req)
@@ -270,11 +271,26 @@ func ListResource(r rest.Lister, rw rest.Watcher, scope *RequestScope, forceWatc
 				scope.err(err, w, req)
 				return
 			}
-			requestInfo, _ := request.RequestInfoFrom(ctx)
-			metrics.RecordLongRunning(req, requestInfo, metrics.APIServerComponent, func() {
-				defer watcher.Stop()
-				handler.ServeHTTP(w, req)
-			})
+			// Invalidate cancel() to defer until serve() is complete.
+			deferredCancel := cancel
+			cancel = func() {}
+
+			serve := func() {
+				defer deferredCancel()
+				requestInfo, _ := request.RequestInfoFrom(ctx)
+				metrics.RecordLongRunning(req, requestInfo, metrics.APIServerComponent, func() {
+					defer watcher.Stop()
+					handler.ServeHTTP(w, req)
+				})
+			}
+
+			// Run watch serving in a separate goroutine to allow freeing current stack memory
+			t := genericfilters.TaskFrom(req.Context())
+			if t != nil {
+				t.Func = serve
+			} else {
+				serve()
+			}
 			return
 		}
 

staging/src/k8s.io/apiserver/pkg/features/kube_features.go

@@ -90,6 +90,12 @@ const (
 	// Add support for distributed tracing in the API Server
 	APIServerTracing featuregate.Feature = "APIServerTracing"
 
+	// owner: @linxiulei
+	// beta: v1.30
+	//
+	// Enables serving watch requests in separate goroutines.
+	APIServingWithRoutine featuregate.Feature = "APIServingWithRoutine"
+
 	// owner: @cici37 @jpbetz
 	// kep: http://kep.k8s.io/3488
 	// alpha: v1.26
@@ -284,6 +290,8 @@ var defaultKubernetesFeatureGates = map[featuregate.Feature]featuregate.FeatureS
 
 	APIServerTracing: {Default: true, PreRelease: featuregate.Beta},
 
+	APIServingWithRoutine: {Default: true, PreRelease: featuregate.Beta},
+
 	ValidatingAdmissionPolicy: {Default: false, PreRelease: featuregate.Beta},
 
 	CustomResourceValidationExpressions: {Default: true, PreRelease: featuregate.GA, LockToDefault: true}, // remove in 1.31

staging/src/k8s.io/apiserver/pkg/server/config.go

@@ -1043,6 +1043,12 @@ func DefaultBuildHandlerChain(apiHandler http.Handler, c *Config) http.Handler {
 		handler = genericapifilters.WithTracing(handler, c.TracerProvider)
 	}
 	handler = genericapifilters.WithLatencyTrackers(handler)
+	// WithRoutine will execute future handlers in a separate goroutine and serving
+	// handler in current goroutine to minimize the stack memory usage. It must be
+	// after WithPanicRecover() to be protected from panics.
+	if utilfeature.DefaultFeatureGate.Enabled(genericfeatures.APIServingWithRoutine) {
+		handler = genericfilters.WithRoutine(handler, c.LongRunningFunc)
+	}
 	handler = genericapifilters.WithRequestInfo(handler, c.RequestInfoResolver)
 	handler = genericapifilters.WithRequestReceivedTimestamp(handler)
 	handler = genericapifilters.WithMuxAndDiscoveryComplete(handler, c.lifecycleSignals.MuxAndDiscoveryComplete.Signaled())

staging/src/k8s.io/apiserver/pkg/server/filters/routine.go

@@ -0,0 +1,77 @@
+/*
+Copyright 2023 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package filters
+
+import (
+	"context"
+	"net/http"
+
+	"k8s.io/apiserver/pkg/endpoints/request"
+)
+
+type taskKeyType int
+
+const taskKey taskKeyType = iota
+
+type Task struct {
+	Func func()
+}
+
+func WithTask(parent context.Context, t *Task) context.Context {
+	return request.WithValue(parent, taskKey, t)
+}
+
+func TaskFrom(ctx context.Context) *Task {
+	t, _ := ctx.Value(taskKey).(*Task)
+	return t
+}
+
+// WithRoutine returns an http.Handler that executes preparation of long running requests (i.e. watches)
+// in a separate Goroutine and then serves the long running request in the main Goroutine. Doing so allows
+// freeing stack memory used in preparation Goroutine for better memory efficiency.
+func WithRoutine(handler http.Handler, longRunning request.LongRunningRequestCheck) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		ctx := req.Context()
+		requestInfo, _ := request.RequestInfoFrom(ctx)
+		if !longRunning(req, requestInfo) {
+			handler.ServeHTTP(w, req)
+			return
+		}
+
+		req = req.WithContext(WithTask(ctx, &Task{}))
+		panicCh := make(chan any, 1)
+		go func() {
+			defer func() {
+				if r := recover(); r != nil {
+					panicCh <- r
+				}
+				close(panicCh)
+			}()
+			handler.ServeHTTP(w, req)
+		}()
+
+		if p, ok := <-panicCh; ok {
+			panic(p)
+		}
+
+		ctx = req.Context()
+		if t := TaskFrom(ctx); t != nil && t.Func != nil {
+			t.Func()
+		}
+
+	})
+}

staging/src/k8s.io/apiserver/pkg/server/filters/routine_test.go

@@ -0,0 +1,79 @@
+/*
+Copyright 2023 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package filters
+
+import (
+	"bytes"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"k8s.io/apimachinery/pkg/util/sets"
+	"k8s.io/apiserver/pkg/endpoints/request"
+	"k8s.io/klog/v2"
+)
+
+func TestPropogatingPanic(t *testing.T) {
+	var buf bytes.Buffer
+	klog.SetOutput(&buf)
+	klog.LogToStderr(false)
+	defer klog.LogToStderr(true)
+
+	panicMsg := "panic as designed"
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		panic(panicMsg)
+	})
+	resolver := &request.RequestInfoFactory{
+		APIPrefixes:          sets.NewString("api", "apis"),
+		GrouplessAPIPrefixes: sets.NewString("api"),
+	}
+	ts := httptest.NewServer(WithRoutine(WithPanicRecovery(handler, resolver), func(_ *http.Request, _ *request.RequestInfo) bool { return true }))
+	defer ts.Close()
+	_, err := http.Get(ts.URL)
+	if err == nil {
+		t.Error("expected to receive an error")
+	}
+
+	klog.Flush()
+	klog.SetOutput(&bytes.Buffer{}) // prevent further writes into buf
+	capturedOutput := buf.String()
+
+	if !strings.Contains(capturedOutput, panicMsg) || !strings.Contains(capturedOutput, "apiserver panic'd") {
+		t.Errorf("unexpected out captured actual = %v", capturedOutput)
+	}
+}
+
+func TestExecutionWithRoutine(t *testing.T) {
+	var executed bool
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		t := TaskFrom(r.Context())
+		t.Func = func() {
+			executed = true
+		}
+	})
+	ts := httptest.NewServer(WithRoutine(handler, func(_ *http.Request, _ *request.RequestInfo) bool { return true }))
+	defer ts.Close()
+
+	_, err := http.Get(ts.URL)
+	if err != nil {
+		t.Errorf("got unexpected error on request: %v", err)
+	}
+	if !executed {
+		t.Error("expected to execute")
+	}
+}