re-submit #4707 (#4730)

go.mod

@@ -42,9 +42,9 @@ require (
 	k8s.io/apiserver v0.18.12
 	k8s.io/client-go v11.0.1-0.20190805182717-6502b5e7b1b5+incompatible
 	k8s.io/utils v0.0.0-20200603063816-c1c6865ac451
-	knative.dev/hack v0.0.0-20201214230143-4ed1ecb8db24
-	knative.dev/pkg v0.0.0-20210107022335-51c72e24c179
-	knative.dev/reconciler-test v0.0.0-20210108100436-db4d65735605
+	knative.dev/hack v0.0.0-20210112093330-d946d2557383
+	knative.dev/pkg v0.0.0-20210112143930-acbf2af596cf
+	knative.dev/reconciler-test v0.0.0-20210111135237-9b251467ccb6
 	sigs.k8s.io/yaml v1.2.0
 )
 

go.sum

@@ -1098,10 +1098,14 @@ k8s.io/utils v0.0.0-20200603063816-c1c6865ac451 h1:v8ud2Up6QK1lNOKFgiIVrZdMg7Mpm
 k8s.io/utils v0.0.0-20200603063816-c1c6865ac451/go.mod h1:jPW/WVKK9YHAvNhRxK0md/EJ228hCsBRufyofKtW8HA=
 knative.dev/hack v0.0.0-20201214230143-4ed1ecb8db24 h1:kIztWfvnIFV8Lhlea02K3YO2mIzcDyQNzrBLn0Oq9sA=
 knative.dev/hack v0.0.0-20201214230143-4ed1ecb8db24/go.mod h1:PHt8x8yX5Z9pPquBEfIj0X66f8iWkWfR0S/sarACJrI=
+knative.dev/hack v0.0.0-20210112093330-d946d2557383 h1:YDYKfHaplhMelgOVP8eRvHlYf5elgZveo36GBDFfDqA=
+knative.dev/hack v0.0.0-20210112093330-d946d2557383/go.mod h1:PHt8x8yX5Z9pPquBEfIj0X66f8iWkWfR0S/sarACJrI=
 knative.dev/pkg v0.0.0-20210107022335-51c72e24c179 h1:lkrgrv69iUk2qhOG9symy15kJUaJZmMybSloi7C3gIw=
 knative.dev/pkg v0.0.0-20210107022335-51c72e24c179/go.mod h1:hckgW978SdzPA2H5EDvRPY8xsnPuDZLJLbPf8Jte7Q0=
-knative.dev/reconciler-test v0.0.0-20210108100436-db4d65735605 h1:gTcj4/ULCzgXEtW+sSd08C5LE3dcPGHU+6/wLT+PVMU=
-knative.dev/reconciler-test v0.0.0-20210108100436-db4d65735605/go.mod h1:rmQpZseeqDpg6/ToFzIeV5hTRkOJujaXBCK7iYL7M4E=
+knative.dev/pkg v0.0.0-20210112143930-acbf2af596cf h1:6/VyHMk6pa395xWho0KLfVj+7NNrmlO7Ki9jLbVjoaI=
+knative.dev/pkg v0.0.0-20210112143930-acbf2af596cf/go.mod h1:hckgW978SdzPA2H5EDvRPY8xsnPuDZLJLbPf8Jte7Q0=
+knative.dev/reconciler-test v0.0.0-20210111135237-9b251467ccb6 h1:VE3bjgOLAekEujKZizi9dtl40TsOloowOjy/fCR77LA=
+knative.dev/reconciler-test v0.0.0-20210111135237-9b251467ccb6/go.mod h1:rmQpZseeqDpg6/ToFzIeV5hTRkOJujaXBCK7iYL7M4E=
 pgregory.net/rapid v0.3.3 h1:jCjBsY4ln4Atz78QoBWxUEvAHaFyNDQg9+WU62aCn1U=
 pgregory.net/rapid v0.3.3/go.mod h1:UYpPVyjFHzYBGHIxLFoupi8vwk6rXNzRY9OMvVxFIOU=
 rsc.io/binaryregexp v0.2.0/go.mod h1:qTv7/COck+e2FymRvadv62gMdZztPaShugOCi3I+8D8=

pkg/kncloudevents/message_receiver.go

@@ -37,6 +37,8 @@ type HTTPMessageReceiver struct {
 
 	server   *http.Server
 	listener net.Listener
+
+	checker http.HandlerFunc
 }
 
 // HTTPMessageReceiverOption enables further configuration of a HTTPMessageReceiver.
@@ -52,6 +54,16 @@ func NewHTTPMessageReceiver(port int, o ...HTTPMessageReceiverOption) *HTTPMessa
 	return h
 }
 
+// WithChecker takes a handler func which will run as an additional health check in Drainer.
+// kncloudevents HTTPMessageReceiver uses Drainer to perform health check.
+// By default, Drainer directly writes StatusOK to kubelet probe if the Pod is not draining.
+// Users can configure customized liveness and readiness check logic by defining checker here.
+func WithChecker(checker http.HandlerFunc) HTTPMessageReceiverOption {
+	return func(h *HTTPMessageReceiver) {
+		h.checker = checker
+	}
+}
+
 // Blocking
 func (recv *HTTPMessageReceiver) StartListen(ctx context.Context, handler http.Handler) error {
 	var err error
@@ -60,7 +72,8 @@ func (recv *HTTPMessageReceiver) StartListen(ctx context.Context, handler http.H
 	}
 
 	drainer := &handlers.Drainer{
-		Inner: CreateHandler(handler),
+		Inner:       CreateHandler(handler),
+		HealthCheck: recv.checker,
 	}
 	recv.server = &http.Server{
 		Addr:    recv.listener.Addr().String(),

vendor/knative.dev/pkg/network/handlers/drain.go

@@ -47,7 +47,8 @@ var newTimer = func(d time.Duration) timer {
 }
 
 // Drainer wraps an inner http.Handler to support responding to kubelet
-// probes and KProbes with a "200 OK" until the handler is told to Drain.
+// probes and KProbes with a "200 OK" until the handler is told to Drain,
+// or Drainer will optionally run the HealthCheck if it is defined.
 // When the Drainer is told to Drain, it will immediately start to fail
 // probes with a "500 shutting down", and the call will block until no
 // requests have been received for QuietPeriod (defaults to
@@ -56,6 +57,10 @@ type Drainer struct {
 	// Mutex guards the initialization and resets of the timer
 	sync.RWMutex
 
+	// HealthCheck is an optional health check that is performed until the drain signal is received.
+	// When unspecified, a "200 OK" is returned, otherwise this function is invoked.
+	HealthCheck http.HandlerFunc
+
 	// Inner is the http.Handler to which we delegate actual requests.
 	Inner http.Handler
 
@@ -78,6 +83,8 @@ func (d *Drainer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	if network.IsKubeletProbe(r) { // Respond to probes regardless of path.
 		if d.draining() {
 			http.Error(w, "shutting down", http.StatusServiceUnavailable)
+		} else if d.HealthCheck != nil {
+			d.HealthCheck(w, r)
 		} else {
 			w.WriteHeader(http.StatusOK)
 		}

vendor/modules.txt

@@ -966,11 +966,11 @@ k8s.io/utils/buffer
 k8s.io/utils/integer
 k8s.io/utils/pointer
 k8s.io/utils/trace
-# knative.dev/hack v0.0.0-20201214230143-4ed1ecb8db24
+# knative.dev/hack v0.0.0-20210112093330-d946d2557383
 ## explicit
 knative.dev/hack
 knative.dev/hack/shell
-# knative.dev/pkg v0.0.0-20210107022335-51c72e24c179
+# knative.dev/pkg v0.0.0-20210112143930-acbf2af596cf
 ## explicit
 knative.dev/pkg/apiextensions/storageversion
 knative.dev/pkg/apiextensions/storageversion/cmd/migrate
@@ -1097,7 +1097,7 @@ knative.dev/pkg/webhook/resourcesemantics
 knative.dev/pkg/webhook/resourcesemantics/conversion
 knative.dev/pkg/webhook/resourcesemantics/defaulting
 knative.dev/pkg/webhook/resourcesemantics/validation
-# knative.dev/reconciler-test v0.0.0-20210108100436-db4d65735605
+# knative.dev/reconciler-test v0.0.0-20210111135237-9b251467ccb6
 ## explicit
 knative.dev/reconciler-test/cmd/eventshub
 knative.dev/reconciler-test/pkg/environment