kubelet默认会每5分钟一次更新node status，包括更新lastHeartbeatTime。 更新周期是由node-status-update-frequency 控制的

  1. // syncNodeStatus should be called periodically from a goroutine.
  2. // It synchronizes node status to master if there is any change or enough time
  3. // passed from the last sync, registering the kubelet first if necessary.
  4. func (kl *Kubelet) syncNodeStatus() {
  5.     kl.syncNodeStatusMux.Lock()
  6.     defer kl.syncNodeStatusMux.Unlock()
  8.     if kl.kubeClient == nil || kl.heartbeatClient == nil {
  9.         return
  10.     }
  11.     if kl.registerNode {
  12.         // This will exit immediately if it doesn't need to do anything.
  13.         kl.registerWithAPIServer()
  14.     }
  15.     if err := kl.updateNodeStatus(); err != nil {
  16.         klog.ErrorS(err, "Unable to update node status")
  17.     }
  18. }

lease

为了减轻apiserver、etcd的压力，使用lease来做更短的心跳保持。
kubelet中有nodeLeaseController，默认每10s一次，定时更新lease信息。