kubelet: only emit one reboot event

There are cases when the kubelet is starting where networking, or other
components can cause the kubelet to not post the status with the bootId.
The failed status update will cause the Kubelet to queue the
NodeRebooted warning and sometimes cause many events to be created.

This fix wraps the recordEventFunc to only emit one message per kubelet
instantiation.

Author: rphillips

pkg/kubelet/nodestatus/setters.go

@@ -23,6 +23,7 @@ import (
 	"net"
 	goruntime "runtime"
 	"strings"
+	"sync"
 	"time"
 
 	cadvisorapiv1 "github.com/google/cadvisor/info/v1"
@@ -57,6 +58,9 @@ const (
 // Setters may partially mutate the node before returning an error.
 type Setter func(ctx context.Context, node *v1.Node) error
 
+// Only emit one reboot event
+var rebootEvent sync.Once
+
 // NodeAddress returns a Setter that updates address-related information on the node.
 func NodeAddress(nodeIPs []net.IP, // typically Kubelet.nodeIPs
 	validateNodeIPFunc func(net.IP) error, // typically Kubelet.nodeIPValidator
@@ -250,6 +254,7 @@ func hasAddressType(addresses []v1.NodeAddress, addressType v1.NodeAddressType)
 	}
 	return false
 }
+
 func hasAddressValue(addresses []v1.NodeAddress, addressValue string) bool {
 	for _, address := range addresses {
 		if address.Address == addressValue {
@@ -311,8 +316,12 @@ func MachineInfo(nodeName string,
 				node.Status.NodeInfo.BootID != info.BootID {
 				// TODO: This requires a transaction, either both node status is updated
 				// and event is recorded or neither should happen, see issue #6055.
-				recordEventFunc(v1.EventTypeWarning, events.NodeRebooted,
-					fmt.Sprintf("Node %s has been rebooted, boot id: %s", nodeName, info.BootID))
+				//
+				// Only emit one reboot event. recordEventFunc queues events and can emit many superfluous reboot events
+				rebootEvent.Do(func() {
+					recordEventFunc(v1.EventTypeWarning, events.NodeRebooted,
+						fmt.Sprintf("Node %s has been rebooted, boot id: %s", nodeName, info.BootID))
+				})
 			}
 			node.Status.NodeInfo.BootID = info.BootID