Add a benchmark for the entire handler chain of the activator (#11014)

cmd/activator/main.go

@@ -175,7 +175,7 @@ func main() {
 
 	// Create activation handler chain
 	// Note: innermost handlers are specified first, ie. the last handler in the chain will be executed first
-	var ah http.Handler = activatorhandler.New(ctx, throttler, transport, logger)
+	ah := activatorhandler.New(ctx, throttler, transport, logger)
 	ah = concurrencyReporter.Handler(ah)
 	ah = tracing.HTTPSpanMiddleware(ah)
 	ah = configStore.HTTPMiddleware(ah)

pkg/activator/handler/main_test.go

@@ -0,0 +1,118 @@
+/*
+Copyright 2021 The Knative 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 handler
+
+import (
+	"bytes"
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	network "knative.dev/networking/pkg"
+	"knative.dev/pkg/logging"
+	pkgnet "knative.dev/pkg/network"
+	rtesting "knative.dev/pkg/reconciler/testing"
+	"knative.dev/pkg/tracing"
+	"knative.dev/serving/pkg/activator"
+	asmetrics "knative.dev/serving/pkg/autoscaler/metrics"
+	pkghttp "knative.dev/serving/pkg/http"
+)
+
+// BenchmarkHandlerChain is supposed to try to project the entire handler chain of the
+// activator to enable us to see improvements that span handlers and to judge some of
+// the handlers that are not developed here.
+func BenchmarkHandlerChain(b *testing.B) {
+	ctx, cancel, _ := rtesting.SetupFakeContextWithCancel(&testing.T{})
+	b.Cleanup(cancel)
+
+	logger := logging.FromContext(ctx)
+	configStore := setupConfigStore(&testing.T{}, logger)
+	revision := revision(testNamespace, testRevName)
+	revisionInformer(ctx, revision)
+
+	// Buffer equal to the activator.
+	statCh := make(chan []asmetrics.StatMessage)
+	concurrencyReporter := NewConcurrencyReporter(ctx, activatorPodName, statCh)
+	go concurrencyReporter.Run(ctx.Done())
+
+	// Just read and ignore all stat messages.
+	go func() {
+		for {
+			select {
+			case <-statCh:
+			case <-ctx.Done():
+				return
+			}
+		}
+	}()
+
+	body := []byte(randomString(1024))
+	rt := pkgnet.RoundTripperFunc(func(*http.Request) (*http.Response, error) {
+		return &http.Response{
+			Body:       ioutil.NopCloser(bytes.NewReader(body)),
+			StatusCode: http.StatusOK,
+		}, nil
+	})
+
+	// Make sure to update this if the activator's main file changes.
+	ah := New(ctx, fakeThrottler{}, rt, logger)
+	ah = concurrencyReporter.Handler(ah)
+	ah = tracing.HTTPSpanMiddleware(ah)
+	ah = configStore.HTTPMiddleware(ah)
+	ah, _ = pkghttp.NewRequestLogHandler(ah, ioutil.Discard, "", nil, false)
+	ah = NewMetricHandler(activatorPodName, ah)
+	ah = NewContextHandler(ctx, ah)
+	ah = &ProbeHandler{NextHandler: ah}
+	ah = network.NewProbeHandler(ah)
+	ah = &HealthHandler{HealthCheck: func() error { return nil }, NextHandler: ah, Logger: logger}
+
+	request := func() *http.Request {
+		req := httptest.NewRequest(http.MethodGet, "http://example.com", nil)
+		req.Host = "test-host"
+		req.Header.Set(activator.RevisionHeaderNamespace, testNamespace)
+		req.Header.Set(activator.RevisionHeaderName, testRevName)
+		return req
+	}
+
+	test := func(req *http.Request, b *testing.B) {
+		resp := &responseRecorder{}
+		ah.ServeHTTP(resp, req)
+		if resp.code != http.StatusOK {
+			b.Fatalf("resp.Code = %d, want: StatusOK(200)", resp.code)
+		}
+		if got, want := resp.size.Load(), int32(len(body)); got != want {
+			b.Fatalf("|body| = %d, want = %d", got, want)
+		}
+	}
+
+	b.Run("sequential", func(b *testing.B) {
+		req := request()
+		for j := 0; j < b.N; j++ {
+			test(req, b)
+		}
+	})
+
+	b.Run("parallel", func(b *testing.B) {
+		b.RunParallel(func(pb *testing.PB) {
+			req := request()
+			for pb.Next() {
+				test(req, b)
+			}
+		})
+	})
+}