implement healthz

for controller managers.

staging/src/k8s.io/controller-manager/pkg/healthz/handler.go

@@ -0,0 +1,68 @@
+/*
+Copyright 2021 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 healthz
+
+import (
+	"net/http"
+	"sync"
+
+	"k8s.io/apiserver/pkg/server/healthz"
+	"k8s.io/apiserver/pkg/server/mux"
+)
+
+// MutableHealthzHandler returns a http.Handler that handles "/healthz"
+// following the standard healthz mechanism.
+//
+// This handler can register health checks after its creation, which
+// is originally not allowed with standard healthz handler.
+type MutableHealthzHandler struct {
+	// handler is the underlying handler that will be replaced every time
+	// new checks are added.
+	handler http.Handler
+	// mutex is a RWMutex that allows concurrent health checks (read)
+	// but disallow replacing the handler at the same time (write).
+	mutex  sync.RWMutex
+	checks []healthz.HealthChecker
+}
+
+func (h *MutableHealthzHandler) ServeHTTP(writer http.ResponseWriter, request *http.Request) {
+	h.mutex.RLock()
+	defer h.mutex.RUnlock()
+
+	h.handler.ServeHTTP(writer, request)
+}
+
+// AddHealthChecker adds health check(s) to the handler.
+//
+// Every time this function is called, the handler have to be re-initiated.
+// It is advised to add as many checks at once as possible.
+func (h *MutableHealthzHandler) AddHealthChecker(checks ...healthz.HealthChecker) {
+	h.mutex.Lock()
+	defer h.mutex.Unlock()
+
+	h.checks = append(h.checks, checks...)
+	newMux := mux.NewPathRecorderMux("healthz")
+	healthz.InstallHandler(newMux, h.checks...)
+	h.handler = newMux
+}
+
+func NewMutableHealthzHandler(checks ...healthz.HealthChecker) *MutableHealthzHandler {
+	h := &MutableHealthzHandler{}
+	h.AddHealthChecker(checks...)
+
+	return h
+}

staging/src/k8s.io/controller-manager/pkg/healthz/handler_test.go

@@ -0,0 +1,174 @@
+/*
+Copyright 2021 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 healthz
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"k8s.io/apiserver/pkg/server/healthz"
+)
+
+func TestMutableHealthzHandler(t *testing.T) {
+	badChecker := healthz.NamedCheck("bad", func(r *http.Request) error {
+		return fmt.Errorf("bad")
+	})
+	for _, tc := range []struct {
+		name           string
+		checkBatches   [][]healthz.HealthChecker
+		appendBad      bool // appends bad check after batches above, and see if it fails afterwards
+		path           string
+		expectedBody   string
+		expectedStatus int
+	}{
+		{
+			name:           "empty",
+			checkBatches:   [][]healthz.HealthChecker{},
+			path:           "/healthz",
+			expectedBody:   "ok",
+			expectedStatus: http.StatusOK,
+		},
+		{
+			name: "good",
+			checkBatches: [][]healthz.HealthChecker{
+				{NamedPingChecker("good")},
+			},
+			path:           "/healthz",
+			expectedBody:   "ok",
+			expectedStatus: http.StatusOK,
+		},
+		{
+			name: "good verbose", // verbose only applies for successful checks
+			checkBatches: [][]healthz.HealthChecker{
+				{NamedPingChecker("good")}, // batch 1: good
+			},
+			path:           "/healthz?verbose=true",
+			expectedBody:   "[+]good ok\nhealthz check passed\n",
+			expectedStatus: http.StatusOK,
+		},
+		{
+			name: "good and bad, same batch",
+			checkBatches: [][]healthz.HealthChecker{
+				{NamedPingChecker("good"), badChecker}, // batch 1: good, bad
+			},
+			path:           "/healthz",
+			expectedBody:   "[+]good ok\n[-]bad failed: reason withheld\nhealthz check failed\n",
+			expectedStatus: http.StatusInternalServerError,
+		},
+		{
+			name: "good and bad, two batches",
+			checkBatches: [][]healthz.HealthChecker{
+				{NamedPingChecker("good")}, // batch 1: good
+				{badChecker},               // batch 2: bad
+			},
+			path:           "/healthz",
+			expectedBody:   "[+]good ok\n[-]bad failed: reason withheld\nhealthz check failed\n",
+			expectedStatus: http.StatusInternalServerError,
+		},
+		{
+			name: "two checks and append bad",
+			checkBatches: [][]healthz.HealthChecker{
+				{NamedPingChecker("foo"), NamedPingChecker("bar")},
+			},
+			path:           "/healthz",
+			expectedBody:   "ok",
+			expectedStatus: http.StatusOK,
+			appendBad:      true,
+		},
+		{
+			name: "subcheck",
+			checkBatches: [][]healthz.HealthChecker{
+				{NamedPingChecker("good")}, // batch 1: good
+				{badChecker},               // batch 2: bad
+			},
+			path:           "/healthz/good",
+			expectedBody:   "ok",
+			expectedStatus: http.StatusOK,
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			h := NewMutableHealthzHandler()
+			for _, batch := range tc.checkBatches {
+				h.AddHealthChecker(batch...)
+			}
+			req, err := http.NewRequest("GET", fmt.Sprintf("https://example.com%v", tc.path), nil)
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+			w := httptest.NewRecorder()
+			h.ServeHTTP(w, req)
+			if w.Code != tc.expectedStatus {
+				t.Errorf("unexpected status: expected %v, got %v", tc.expectedStatus, w.Result().StatusCode)
+			}
+			if w.Body.String() != tc.expectedBody {
+				t.Errorf("unexpected body: expected %v, got %v", tc.expectedBody, w.Body.String())
+			}
+			if tc.appendBad {
+				h.AddHealthChecker(badChecker)
+				w := httptest.NewRecorder()
+				h.ServeHTTP(w, req)
+				// should fail
+				if w.Code != http.StatusInternalServerError {
+					t.Errorf("did not fail after adding bad checker")
+				}
+			}
+		})
+	}
+}
+
+// TestConcurrentChecks tests that the handler would not block on concurrent healthz requests.
+func TestConcurrentChecks(t *testing.T) {
+	const N = 5
+	stopChan := make(chan interface{})
+	defer close(stopChan) // always close no matter passing or not
+	concurrentChan := make(chan interface{}, N)
+	var concurrentCount int32
+	pausingCheck := healthz.NamedCheck("pausing", func(r *http.Request) error {
+		atomic.AddInt32(&concurrentCount, 1)
+		concurrentChan <- nil
+		<-stopChan
+		return nil
+	})
+
+	h := NewMutableHealthzHandler(pausingCheck)
+	for i := 0; i < N; i++ {
+		go func() {
+			req, _ := http.NewRequest(http.MethodGet, "https://example.com/healthz", nil)
+			w := httptest.NewRecorder()
+			h.ServeHTTP(w, req)
+		}()
+	}
+
+	giveUp := time.After(1 * time.Second) // should take <1ms if passing
+	for i := 0; i < N; i++ {
+		select {
+		case <-giveUp:
+			t.Errorf("given up waiting for concurrent checks to start.")
+			return
+		case <-concurrentChan:
+			continue
+		}
+	}
+
+	if concurrentCount != N {
+		t.Errorf("expected %v concurrency, got %v", N, concurrentCount)
+	}
+}

staging/src/k8s.io/controller-manager/pkg/healthz/healthz.go

@@ -0,0 +1,43 @@
+/*
+Copyright 2021 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 healthz
+
+import (
+	"net/http"
+
+	"k8s.io/apiserver/pkg/server/healthz"
+)
+
+// NamedPingChecker returns a health check with given name
+// that returns no error when checked.
+func NamedPingChecker(name string) healthz.HealthChecker {
+	return NamedHealthChecker(name, healthz.PingHealthz)
+}
+
+// NamedHealthChecker creates a named health check from
+// an unnamed one.
+func NamedHealthChecker(name string, check UnnamedHealthChecker) healthz.HealthChecker {
+	return healthz.NamedCheck(name, check.Check)
+}
+
+// UnnamedHealthChecker is an unnamed healthz checker.
+// The name of the check can be set by the controller manager.
+type UnnamedHealthChecker interface {
+	Check(req *http.Request) error
+}
+
+var _ UnnamedHealthChecker = (healthz.HealthChecker)(nil)

staging/src/k8s.io/controller-manager/pkg/healthz/healthz_test.go

@@ -0,0 +1,41 @@
+/*
+Copyright 2021 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 healthz
+
+import (
+	"fmt"
+	"net/http"
+	"testing"
+)
+
+type checkWithMessage struct {
+	message string
+}
+
+func (c *checkWithMessage) Check(_ *http.Request) error {
+	return fmt.Errorf("%s", c.message)
+}
+
+func TestNamedHealthChecker(t *testing.T) {
+	named := NamedHealthChecker("foo", &checkWithMessage{message: "hello"})
+	if named.Name() != "foo" {
+		t.Errorf("expected: %v, got: %v", "foo", named.Name())
+	}
+	if err := named.Check(nil); err.Error() != "hello" {
+		t.Errorf("expected: %v, got: %v", "hello", err.Error())
+	}
+}