Remove unnecessary restarts of metricsets while using Node autodiscover

CHANGELOG.next.asciidoc

@@ -148,6 +148,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Fix metrics hints builder to avoid wrong container metadata usage when port is not exposed {pull}18979[18979]
 - Server-side TLS config now validates certificate and key are both specified {pull}19584[19584]
 - Fix seccomp policy for calls to `chmod` and `chown`. {pull}20054[20054]
+- Remove unnecessary restarts of metricsets while using Node autodiscover {pull}19974[19974]
 
 *Auditbeat*
 

libbeat/autodiscover/providers/kubernetes/node.go

@@ -23,6 +23,7 @@ import (
 
 	"github.com/gofrs/uuid"
 	v1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/api/equality"
 	k8s "k8s.io/client-go/kubernetes"
 
 	"github.com/elastic/beats/v7/libbeat/autodiscover/builder"
@@ -66,6 +67,7 @@ func NewNodeEventer(uuid uuid.UUID, cfg *common.Config, client k8s.Interface, pu
 	watcher, err := kubernetes.NewWatcher(client, &kubernetes.Node{}, kubernetes.WatchOptions{
 		SyncTimeout: config.SyncPeriod,
 		Node:        config.Node,
+		IsUpdated:   isUpdated,
 	}, nil)
 
 	if err != nil {
@@ -190,6 +192,40 @@ func (n *node) emit(node *kubernetes.Node, flag string) {
 	n.publish(event)
 }
 
+func isUpdated(o, n interface{}) bool {
+	old, _ := o.(*kubernetes.Node)
+	new, _ := n.(*kubernetes.Node)
+
+	// Consider as not update in case one of the two objects is not a Node
+	if old == nil || new == nil {
+		return true
+	}
+
+	// This is a resync. It is not an update
+	if old.ResourceVersion == new.ResourceVersion {
+		return false
+	}
+
+	// If the old object and new object are different
+	oldCopy := old.DeepCopy()
+	oldCopy.ResourceVersion = ""
+
+	newCopy := new.DeepCopy()
+	newCopy.ResourceVersion = ""
+
+	// If the old object and new object are different in either meta or spec then there is a valid change
+	fmt.Println(equality.Semantic.DeepDerivative(oldCopy.Spec, newCopy.Spec), equality.Semantic.DeepDerivative(oldCopy.ObjectMeta, newCopy.ObjectMeta))
+	if !equality.Semantic.DeepEqual(oldCopy.Spec, newCopy.Spec) || !equality.Semantic.DeepEqual(oldCopy.ObjectMeta, newCopy.ObjectMeta) {
+		return true
+	}
+
+	// If there is a change in the node status then there is a valid change.
+	if isNodeReady(old) != isNodeReady(new) {
+		return true
+	}
+	return false
+}
+
 func getAddress(node *kubernetes.Node) string {
 	for _, address := range node.Status.Addresses {
 		if address.Type == v1.NodeExternalIP && address.Address != "" {

libbeat/autodiscover/providers/kubernetes/node_test.go

@@ -278,3 +278,178 @@ func TestEmitEvent_Node(t *testing.T) {
 		})
 	}
 }
+
+func TestNode_isUpdated(t *testing.T) {
+	tests := []struct {
+		old     *kubernetes.Node
+		new     *kubernetes.Node
+		updated bool
+		test    string
+	}{
+		{
+			test:    "one of the objects is nil then its updated",
+			old:     nil,
+			new:     &kubernetes.Node{},
+			updated: true,
+		},
+		{
+			test:    "both empty nodes should return not updated",
+			old:     &kubernetes.Node{},
+			new:     &kubernetes.Node{},
+			updated: false,
+		},
+		{
+			test: "resource version is the same should return not updated",
+			old: &kubernetes.Node{
+				ObjectMeta: kubernetes.ObjectMeta{
+					ResourceVersion: "1",
+				},
+			},
+			new: &kubernetes.Node{
+				ObjectMeta: kubernetes.ObjectMeta{
+					ResourceVersion: "1",
+				},
+			},
+		},
+		{
+			test: "if meta changes then it should return updated",
+			old: &kubernetes.Node{
+				ObjectMeta: kubernetes.ObjectMeta{
+					ResourceVersion: "1",
+					Annotations:     map[string]string{},
+				},
+			},
+			new: &kubernetes.Node{
+				ObjectMeta: kubernetes.ObjectMeta{
+					ResourceVersion: "2",
+					Annotations: map[string]string{
+						"a": "b",
+					},
+				},
+			},
+			updated: true,
+		},
+		{
+			test: "if spec changes then it should return updated",
+			old: &kubernetes.Node{
+				ObjectMeta: kubernetes.ObjectMeta{
+					ResourceVersion: "1",
+					Annotations: map[string]string{
+						"a": "b",
+					},
+				},
+				Spec: v1.NodeSpec{
+					ProviderID:    "1",
+					Unschedulable: false,
+				},
+			},
+			new: &kubernetes.Node{
+				ObjectMeta: kubernetes.ObjectMeta{
+					ResourceVersion: "2",
+					Annotations: map[string]string{
+						"a": "b",
+					},
+				},
+				Spec: v1.NodeSpec{
+					ProviderID:    "1",
+					Unschedulable: true,
+				},
+			},
+			updated: true,
+		},
+		{
+			test: "if overall status doesn't change then its not an update",
+			old: &kubernetes.Node{
+				ObjectMeta: kubernetes.ObjectMeta{
+					ResourceVersion: "1",
+					Annotations: map[string]string{
+						"a": "b",
+					},
+				},
+				Spec: v1.NodeSpec{
+					ProviderID:    "1",
+					Unschedulable: true,
+				},
+				Status: v1.NodeStatus{
+					Conditions: []v1.NodeCondition{
+						{
+							Type:   v1.NodeReady,
+							Status: v1.ConditionTrue,
+						},
+					},
+				},
+			},
+			new: &kubernetes.Node{
+				ObjectMeta: kubernetes.ObjectMeta{
+					ResourceVersion: "2",
+					Annotations: map[string]string{
+						"a": "b",
+					},
+				},
+				Spec: v1.NodeSpec{
+					ProviderID:    "1",
+					Unschedulable: true,
+				},
+				Status: v1.NodeStatus{
+					Conditions: []v1.NodeCondition{
+						{
+							Type:   v1.NodeReady,
+							Status: v1.ConditionTrue,
+						},
+					},
+				},
+			},
+			updated: false,
+		},
+		{
+			test: "if node status changes then its an update",
+			old: &kubernetes.Node{
+				ObjectMeta: kubernetes.ObjectMeta{
+					ResourceVersion: "1",
+					Annotations: map[string]string{
+						"a": "b",
+					},
+				},
+				Spec: v1.NodeSpec{
+					ProviderID:    "1",
+					Unschedulable: true,
+				},
+				Status: v1.NodeStatus{
+					Conditions: []v1.NodeCondition{
+						{
+							Type:   v1.NodeReady,
+							Status: v1.ConditionFalse,
+						},
+					},
+				},
+			},
+			new: &kubernetes.Node{
+				ObjectMeta: kubernetes.ObjectMeta{
+					ResourceVersion: "2",
+					Annotations: map[string]string{
+						"a": "b",
+					},
+				},
+				Spec: v1.NodeSpec{
+					ProviderID:    "1",
+					Unschedulable: true,
+				},
+				Status: v1.NodeStatus{
+					Conditions: []v1.NodeCondition{
+						{
+							Type:   v1.NodeReady,
+							Status: v1.ConditionTrue,
+						},
+					},
+				},
+			},
+			updated: true,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.test, func(t *testing.T) {
+			assert.Equal(t, test.updated, isUpdated(test.old, test.new))
+		})
+	}
+}

libbeat/common/kubernetes/watcher.go

@@ -66,6 +66,8 @@ type WatchOptions struct {
 	Node string
 	// Namespace is used for filtering watched resource to given namespace, use "" for all namespaces
 	Namespace string
+
+	IsUpdated func(old, new interface{}) bool
 }
 
 type item struct {
@@ -123,7 +125,8 @@ func NewWatcher(client kubernetes.Interface, resource Resource, opts WatchOption
 			new, _ := accessor.ResourceVersion(n.(runtime.Object))
 
 			// Only enqueue changes that have a different resource versions to avoid processing resyncs.
-			if old != new {
+			// Also if there is a registered function to check for updates, use it to check for updates.
+			if old != new && opts.IsUpdated != nil && opts.IsUpdated(o, n) {
 				w.enqueue(n, update)
 			}
 		},