UPSTREAM: 129657: storage/cacher/ready: dynamically calculate the retryAfterSeconds

retryAfterSeconds is based on the time elapsed since the state (ready, unready) was last changed.

Author: bertinatto

staging/src/k8s.io/apiserver/pkg/storage/cacher/cacher.go

@@ -368,7 +368,7 @@ func NewCacherFromConfig(config Config) (*Cacher, error) {
 	objType := reflect.TypeOf(obj)
 	cacher := &Cacher{
 		resourcePrefix: config.ResourcePrefix,
-		ready:          newReady(),
+		ready:          newReady(config.Clock),
 		storage:        config.Storage,
 		objectType:     objType,
 		groupResource:  config.GroupResource,
@@ -537,9 +537,10 @@ func (c *Cacher) Watch(ctx context.Context, key string, opts storage.ListOptions
 	var readyGeneration int
 	if utilfeature.DefaultFeatureGate.Enabled(features.ResilientWatchCacheInitialization) {
 		var ok bool
-		readyGeneration, ok = c.ready.checkAndReadGeneration()
+		var downtime time.Duration
+		readyGeneration, downtime, ok = c.ready.checkAndReadGeneration()
 		if !ok {
-			return nil, errors.NewTooManyRequests("storage is (re)initializing", 1)
+			return nil, errors.NewTooManyRequests("storage is (re)initializing", calculateRetryAfterForUnreadyCache(downtime))
 		}
 	} else {
 		readyGeneration, err = c.ready.waitAndReadGeneration(ctx)
@@ -660,7 +661,7 @@ func (c *Cacher) Watch(ctx context.Context, key string, opts storage.ListOptions
 		c.Lock()
 		defer c.Unlock()
 
-		if generation, ok := c.ready.checkAndReadGeneration(); generation != readyGeneration || !ok {
+		if generation, _, ok := c.ready.checkAndReadGeneration(); generation != readyGeneration || !ok {
 			// We went unready or are already on a different generation.
 			// Avoid registering and starting the watch as it will have to be
 			// terminated immediately anyway.
@@ -873,10 +874,10 @@ func (c *Cacher) GetList(ctx context.Context, key string, opts storage.ListOptio
 	defer span.End(500 * time.Millisecond)
 
 	if utilfeature.DefaultFeatureGate.Enabled(features.ResilientWatchCacheInitialization) {
-		if !c.ready.check() {
+		if downtime, ok := c.ready.check(); !ok {
 			// If Cacher is not initialized, reject List requests
 			// as described in https://kep.k8s.io/4568
-			return errors.NewTooManyRequests("storage is (re)initializing", 1)
+			return errors.NewTooManyRequests("storage is (re)initializing", calculateRetryAfterForUnreadyCache(downtime))
 		}
 	} else {
 		if err := c.ready.wait(ctx); err != nil {
@@ -1473,7 +1474,11 @@ func (c *Cacher) setInitialEventsEndBookmarkIfRequested(cacheInterval *watchCach
 	}
 }
 
-// errWatcher implements watch.Interface to return a single error
+func (c *Cacher) Ready() bool {
+	_, ok := c.ready.check()
+	return ok
+
+	// errWatcher implements watch.Interface to return a single error
 type errWatcher struct {
 	result chan watch.Event
 }

staging/src/k8s.io/apiserver/pkg/storage/cacher/cacher_whitebox_test.go

@@ -688,7 +688,7 @@ func TestWatchNotHangingOnStartupFailure(t *testing.T) {
 	// constantly failing lists to the underlying storage.
 	dummyErr := fmt.Errorf("dummy")
 	backingStorage := &dummyStorage{err: dummyErr}
-	cacher, _, err := newTestCacherWithoutSyncing(backingStorage)
+	cacher, _, err := newTestCacherWithoutSyncing(backingStorage, testingclock.NewFakeClock(time.Now()))
 	if err != nil {
 		t.Fatalf("Couldn't create cacher: %v", err)
 	}
@@ -3087,3 +3087,44 @@ func TestListIndexer(t *testing.T) {
 		})
 	}
 }
+
+func TestRetryAfterForUnreadyCache(t *testing.T) {
+	if !utilfeature.DefaultFeatureGate.Enabled(features.ResilientWatchCacheInitialization) {
+		t.Skipf("the test requires %v to be enabled", features.ResilientWatchCacheInitialization)
+	}
+	backingStorage := &dummyStorage{}
+	clock := testingclock.NewFakeClock(time.Now())
+	cacher, _, err := newTestCacherWithoutSyncing(backingStorage, clock)
+	if err != nil {
+		t.Fatalf("Couldn't create cacher: %v", err)
+	}
+	defer cacher.Stop()
+	if err = cacher.ready.wait(context.Background()); err != nil {
+		t.Fatalf("Unexpected error waiting for the cache to be ready")
+	}
+
+	cacher.ready.set(false)
+	clock.Step(14 * time.Second)
+
+	opts := storage.ListOptions{
+		ResourceVersion: "0",
+		Predicate:       storage.Everything,
+	}
+	result := &example.PodList{}
+	proxy := NewCacheProxy(cacher, backingStorage)
+	err = proxy.GetList(context.TODO(), "/pods/ns", opts, result)
+
+	if !apierrors.IsTooManyRequests(err) {
+		t.Fatalf("Unexpected GetList error: %v", err)
+	}
+	var statusError apierrors.APIStatus
+	if !errors.As(err, &statusError) {
+		t.Fatalf("Unexpected error: %v, expected apierrors.APIStatus", err)
+	}
+	if statusError.Status().Details == nil {
+		t.Fatalf("Expected to get status details, got none")
+	}
+	if statusError.Status().Details.RetryAfterSeconds != 2 {
+		t.Fatalf("Unexpected retry after: %v", statusError.Status().Details.RetryAfterSeconds)
+	}
+}

staging/src/k8s.io/apiserver/pkg/storage/cacher/ready.go

@@ -20,6 +20,9 @@ import (
 	"context"
 	"fmt"
 	"sync"
+	"time"
+
+	"k8s.io/utils/clock"
 )
 
 type status int
@@ -43,13 +46,20 @@ type ready struct {
 	lock        sync.RWMutex  // protect the state and generation variables
 	restartLock sync.Mutex    // protect the transition from ready to pending where the channel is recreated
 	waitCh      chan struct{} // blocks until is ready or stopped
+
+	clock               clock.Clock
+	lastStateChangeTime time.Time
 }
 
-func newReady() *ready {
-	return &ready{
+func newReady(c clock.Clock) *ready {
+	r := &ready{
 		waitCh: make(chan struct{}),
 		state:  Pending,
+		clock:  c,
 	}
+	r.updateLastStateChangeTimeLocked()
+
+	return r
 }
 
 // done close the channel once the state is Ready or Stopped
@@ -100,17 +110,17 @@ func (r *ready) waitAndReadGeneration(ctx context.Context) (int, error) {
 	}
 }
 
-// check returns true only if it is Ready.
-func (r *ready) check() bool {
-	_, ok := r.checkAndReadGeneration()
-	return ok
+// check returns the time elapsed since the state was last changed and the current value.
+func (r *ready) check() (time.Duration, bool) {
+	_, elapsed, ok := r.checkAndReadGeneration()
+	return elapsed, ok
 }
 
-// checkAndReadGeneration returns the current generation and whether it is Ready.
-func (r *ready) checkAndReadGeneration() (int, bool) {
+// checkAndReadGeneration returns the current generation, the time elapsed since the state was last changed and the current value.
+func (r *ready) checkAndReadGeneration() (int, time.Duration, bool) {
 	r.lock.RLock()
 	defer r.lock.RUnlock()
-	return r.generation, r.state == Ready
+	return r.generation, r.clock.Since(r.lastStateChangeTime), r.state == Ready
 }
 
 // set the state to Pending (false) or Ready (true), it does not have effect if the state is Stopped.
@@ -123,6 +133,7 @@ func (r *ready) set(ok bool) {
 	if ok && r.state == Pending {
 		r.state = Ready
 		r.generation++
+		r.updateLastStateChangeTimeLocked()
 		select {
 		case <-r.waitCh:
 		default:
@@ -139,6 +150,7 @@ func (r *ready) set(ok bool) {
 		default:
 		}
 		r.state = Pending
+		r.updateLastStateChangeTimeLocked()
 	}
 }
 
@@ -148,10 +160,15 @@ func (r *ready) stop() {
 	defer r.lock.Unlock()
 	if r.state != Stopped {
 		r.state = Stopped
+		r.updateLastStateChangeTimeLocked()
 	}
 	select {
 	case <-r.waitCh:
 	default:
 		close(r.waitCh)
 	}
 }
+
+func (r *ready) updateLastStateChangeTimeLocked() {
+	r.lastStateChangeTime = r.clock.Now()
+}

staging/src/k8s.io/apiserver/pkg/storage/cacher/ready_test.go

@@ -21,11 +21,13 @@ import (
 	"sync"
 	"testing"
 	"time"
+
+	testingclock "k8s.io/utils/clock/testing"
 )
 
 func Test_newReady(t *testing.T) {
 	errCh := make(chan error, 10)
-	ready := newReady()
+	ready := newReady(testingclock.NewFakeClock(time.Now()))
 	ready.set(false)
 	// create 10 goroutines waiting for ready
 	for i := 0; i < 10; i++ {
@@ -48,20 +50,20 @@ func Test_newReady(t *testing.T) {
 
 func Test_newReadySetIdempotent(t *testing.T) {
 	errCh := make(chan error, 10)
-	ready := newReady()
+	ready := newReady(testingclock.NewFakeClock(time.Now()))
 	ready.set(false)
 	ready.set(false)
 	ready.set(false)
-	if generation, ok := ready.checkAndReadGeneration(); generation != 0 || ok {
+	if generation, _, ok := ready.checkAndReadGeneration(); generation != 0 || ok {
 		t.Errorf("unexpected state: generation=%v ready=%v", generation, ok)
 	}
 	ready.set(true)
-	if generation, ok := ready.checkAndReadGeneration(); generation != 1 || !ok {
+	if generation, _, ok := ready.checkAndReadGeneration(); generation != 1 || !ok {
 		t.Errorf("unexpected state: generation=%v ready=%v", generation, ok)
 	}
 	ready.set(true)
 	ready.set(true)
-	if generation, ok := ready.checkAndReadGeneration(); generation != 1 || !ok {
+	if generation, _, ok := ready.checkAndReadGeneration(); generation != 1 || !ok {
 		t.Errorf("unexpected state: generation=%v ready=%v", generation, ok)
 	}
 	ready.set(false)
@@ -77,7 +79,7 @@ func Test_newReadySetIdempotent(t *testing.T) {
 		t.Errorf("ready should be blocking")
 	}
 	ready.set(true)
-	if generation, ok := ready.checkAndReadGeneration(); generation != 2 || !ok {
+	if generation, _, ok := ready.checkAndReadGeneration(); generation != 2 || !ok {
 		t.Errorf("unexpected state: generation=%v ready=%v", generation, ok)
 	}
 	for i := 0; i < 10; i++ {
@@ -92,7 +94,7 @@ func Test_newReadySetIdempotent(t *testing.T) {
 func Test_newReadyRacy(t *testing.T) {
 	concurrency := 1000
 	errCh := make(chan error, concurrency)
-	ready := newReady()
+	ready := newReady(testingclock.NewFakeClock(time.Now()))
 	ready.set(false)
 
 	wg := sync.WaitGroup{}
@@ -123,7 +125,7 @@ func Test_newReadyRacy(t *testing.T) {
 
 func Test_newReadyStop(t *testing.T) {
 	errCh := make(chan error, 10)
-	ready := newReady()
+	ready := newReady(testingclock.NewFakeClock(time.Now()))
 	ready.set(false)
 	// create 10 goroutines waiting for ready and stop
 	for i := 0; i < 10; i++ {
@@ -145,24 +147,24 @@ func Test_newReadyStop(t *testing.T) {
 }
 
 func Test_newReadyCheck(t *testing.T) {
-	ready := newReady()
+	ready := newReady(testingclock.NewFakeClock(time.Now()))
 	// it starts as false
-	if ready.check() {
-		t.Errorf("unexpected ready state %v", ready.check())
+	if _, ok := ready.check(); ok {
+		t.Errorf("unexpected ready state %v", ok)
 	}
 	ready.set(true)
-	if !ready.check() {
-		t.Errorf("unexpected ready state %v", ready.check())
+	if _, ok := ready.check(); !ok {
+		t.Errorf("unexpected ready state %v", ok)
 	}
 	// stop sets ready to false
 	ready.stop()
-	if ready.check() {
-		t.Errorf("unexpected ready state %v", ready.check())
+	if _, ok := ready.check(); ok {
+		t.Errorf("unexpected ready state %v", ok)
 	}
 	// can not set to true if is stopped
 	ready.set(true)
-	if ready.check() {
-		t.Errorf("unexpected ready state %v", ready.check())
+	if _, ok := ready.check(); ok {
+		t.Errorf("unexpected ready state %v", ok)
 	}
 	err := ready.wait(context.Background())
 	if err == nil {
@@ -172,7 +174,7 @@ func Test_newReadyCheck(t *testing.T) {
 
 func Test_newReadyCancelPending(t *testing.T) {
 	errCh := make(chan error, 10)
-	ready := newReady()
+	ready := newReady(testingclock.NewFakeClock(time.Now()))
 	ready.set(false)
 	ctx, cancel := context.WithCancel(context.Background())
 	// create 10 goroutines stuck on pending
@@ -193,3 +195,40 @@ func Test_newReadyCancelPending(t *testing.T) {
 		}
 	}
 }
+
+func Test_newReadyStateChangeTimestamp(t *testing.T) {
+	fakeClock := testingclock.NewFakeClock(time.Now())
+	fakeClock.SetTime(time.Now())
+
+	ready := newReady(fakeClock)
+	fakeClock.Step(time.Minute)
+	checkReadyTransitionTime(t, ready, time.Minute)
+
+	ready.set(true)
+	fakeClock.Step(time.Minute)
+	checkReadyTransitionTime(t, ready, time.Minute)
+	fakeClock.Step(time.Minute)
+	checkReadyTransitionTime(t, ready, 2*time.Minute)
+
+	ready.set(false)
+	fakeClock.Step(time.Minute)
+	checkReadyTransitionTime(t, ready, time.Minute)
+	fakeClock.Step(time.Minute)
+	checkReadyTransitionTime(t, ready, 2*time.Minute)
+
+	ready.set(true)
+	fakeClock.Step(time.Minute)
+	checkReadyTransitionTime(t, ready, time.Minute)
+
+	ready.stop()
+	fakeClock.Step(time.Minute)
+	checkReadyTransitionTime(t, ready, time.Minute)
+	fakeClock.Step(time.Minute)
+	checkReadyTransitionTime(t, ready, 2*time.Minute)
+}
+
+func checkReadyTransitionTime(t *testing.T, r *ready, expectedLastStateChangeDuration time.Duration) {
+	if lastStateChangeDuration, _ := r.check(); lastStateChangeDuration != expectedLastStateChangeDuration {
+		t.Errorf("unexpected last state change duration: %v, expected: %v", lastStateChangeDuration, expectedLastStateChangeDuration)
+	}
+}

staging/src/k8s.io/apiserver/pkg/storage/cacher/util.go

@@ -17,7 +17,9 @@ limitations under the License.
 package cacher
 
 import (
+	"math"
 	"strings"
+	"time"
 )
 
 // hasPathPrefix returns true if the string matches pathPrefix exactly, or if is prefixed with pathPrefix at a path segment boundary
@@ -44,3 +46,11 @@ func hasPathPrefix(s, pathPrefix string) bool {
 	}
 	return false
 }
+
+// calculateRetryAfterForUnreadyCache calculates the retry duration based on the cache downtime.
+func calculateRetryAfterForUnreadyCache(downtime time.Duration) int {
+	factor := 0.06
+	result := math.Exp(factor * downtime.Seconds())
+	result = math.Min(30, math.Max(1, result))
+	return int(result)
+}