Add random interval to nodeStatusReport interval every time after an actual node status change

Author: mengqiy

pkg/kubelet/kubelet.go

@@ -1214,6 +1214,12 @@ type Kubelet struct {
 	// status to master. It is only used when node lease feature is enabled.
 	nodeStatusReportFrequency time.Duration
 
+	// delayAfterNodeStatusChange is the one-time random duration that we add to the next node status report interval
+	// every time when there's an actual node status change. But all future node status update that is not caused by
+	// real status change will stick with nodeStatusReportFrequency. The random duration is a uniform distribution over
+	// [-0.5*nodeStatusReportFrequency, 0.5*nodeStatusReportFrequency]
+	delayAfterNodeStatusChange time.Duration
+
 	// lastStatusReportTime is the time when node status was last reported.
 	lastStatusReportTime time.Time
 

pkg/kubelet/kubelet_node_status.go

@@ -19,6 +19,7 @@ package kubelet
 import (
 	"context"
 	"fmt"
+	"math/rand"
 	"net"
 	goruntime "runtime"
 	"sort"
@@ -579,20 +580,42 @@ func (kl *Kubelet) tryUpdateNodeStatus(ctx context.Context, tryNumber int) error
 	}
 
 	node, changed := kl.updateNode(ctx, originalNode)
-	shouldPatchNodeStatus := changed || kl.clock.Since(kl.lastStatusReportTime) >= kl.nodeStatusReportFrequency
-
-	if !shouldPatchNodeStatus {
+	// no need to update the status yet
+	if !changed && !kl.isUpdateStatusPeriodExperid() {
 		kl.markVolumesFromNode(node)
 		return nil
 	}
 
+	// We need to update the node status, if this is caused by a node change we want to calculate a new
+	// random delay so we avoid all the nodes to reach the apiserver at the same time. If the update is not related
+	// to a node change, because we run over the period, we reset the random delay so the node keeps updating
+	// its status at the same cadence
+	if changed {
+		kl.delayAfterNodeStatusChange = kl.calculateDelay()
+	} else {
+		kl.delayAfterNodeStatusChange = 0
+	}
 	updatedNode, err := kl.patchNodeStatus(originalNode, node)
 	if err == nil {
 		kl.markVolumesFromNode(updatedNode)
 	}
 	return err
 }
 
+func (kl *Kubelet) isUpdateStatusPeriodExperid() bool {
+	if kl.lastStatusReportTime.IsZero() {
+		return false
+	}
+	if kl.clock.Since(kl.lastStatusReportTime) >= kl.nodeStatusReportFrequency+kl.delayAfterNodeStatusChange {
+		return true
+	}
+	return false
+}
+
+func (kl *Kubelet) calculateDelay() time.Duration {
+	return time.Duration(float64(kl.nodeStatusReportFrequency) * (-0.5 + rand.Float64()))
+}
+
 // updateNode creates a copy of originalNode and runs update logic on it.
 // It returns the updated node object and a bool indicating if anything has been changed.
 func (kl *Kubelet) updateNode(ctx context.Context, originalNode *v1.Node) (*v1.Node, bool) {

pkg/kubelet/kubelet_node_status_test.go

@@ -3088,3 +3088,67 @@ func TestUpdateNodeAddresses(t *testing.T) {
 		})
 	}
 }
+
+func TestIsUpdateStatusPeriodExperid(t *testing.T) {
+	testcases := []struct {
+		name                       string
+		lastStatusReportTime       time.Time
+		delayAfterNodeStatusChange time.Duration
+		expectExpired              bool
+	}{
+		{
+			name:                       "no status update before and no delay",
+			lastStatusReportTime:       time.Time{},
+			delayAfterNodeStatusChange: 0,
+			expectExpired:              false,
+		},
+		{
+			name:                       "no status update before and existing delay",
+			lastStatusReportTime:       time.Time{},
+			delayAfterNodeStatusChange: 30 * time.Second,
+			expectExpired:              false,
+		},
+		{
+			name:                       "not expired and no delay",
+			lastStatusReportTime:       time.Now().Add(-4 * time.Minute),
+			delayAfterNodeStatusChange: 0,
+			expectExpired:              false,
+		},
+		{
+			name:                       "not expired",
+			lastStatusReportTime:       time.Now().Add(-5 * time.Minute),
+			delayAfterNodeStatusChange: time.Minute,
+			expectExpired:              false,
+		},
+		{
+			name:                       "expired",
+			lastStatusReportTime:       time.Now().Add(-4 * time.Minute),
+			delayAfterNodeStatusChange: -2 * time.Minute,
+			expectExpired:              true,
+		},
+	}
+
+	testKubelet := newTestKubelet(t, false /* controllerAttachDetachEnabled */)
+	defer testKubelet.Cleanup()
+	kubelet := testKubelet.kubelet
+	kubelet.nodeStatusReportFrequency = 5 * time.Minute
+
+	for _, tc := range testcases {
+		kubelet.lastStatusReportTime = tc.lastStatusReportTime
+		kubelet.delayAfterNodeStatusChange = tc.delayAfterNodeStatusChange
+		expired := kubelet.isUpdateStatusPeriodExperid()
+		assert.Equal(t, tc.expectExpired, expired, tc.name)
+	}
+}
+
+func TestCalculateDelay(t *testing.T) {
+	testKubelet := newTestKubelet(t, false /* controllerAttachDetachEnabled */)
+	defer testKubelet.Cleanup()
+	kubelet := testKubelet.kubelet
+	kubelet.nodeStatusReportFrequency = 5 * time.Minute
+
+	for i := 0; i < 100; i++ {
+		randomDelay := kubelet.calculateDelay()
+		assert.LessOrEqual(t, randomDelay.Abs(), kubelet.nodeStatusReportFrequency/2)
+	}
+}