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最近在给k8s 1.8添加磁盘调度的时候，又撸了一遍k8s的相关的源码，之前看过我源码分析的那个是k8s 1.4版本的，1.8版本还是有点变化的。
先看看kubelet上报机制，这个是kubelet的心跳机制，定时上报节点状态，默认是10s，时间可以设定
在kubelet创建的时候就已经创建了节点状态的收集方法
pkg/kubelet/kubelet.go里面NewMainKubelet方法
klet.setNodeStatusFuncs = klet.defaultNodeStatusFuncs()那默认的方法有哪些呢？
// defaultNodeStatusFuncs is a factory that generates the default set of
// setNodeStatus funcs
func (kl *Kubelet) defaultNodeStatusFuncs() []func(*v1.Node) error {// initial set of node status update handlers, can be modified by Option'swithoutError := func(f func(*v1.Node)) func(*v1.Node) error {return func(n *v1.Node) error {f(n)return nil}}return []func(*v1.Node) error{kl.setNodeAddress,withoutError(kl.setNodeStatusInfo),withoutError(kl.setNodeOODCondition),withoutError(kl.setNodeMemoryPressureCondition),withoutError(kl.setNodeDiskPressureCondition),withoutError(kl.setNodeDiskMountPressureCondition),withoutError(kl.setNodeReadyCondition),withoutError(kl.setNodeVolumesInUseStatus),withoutError(kl.recordNodeSchedulableEvent),}
}注意上面的setNodeDiskMountPressureCondition这个是我自己添加上面的，不是k8s自带。这个里面包括节点信息、节点OOD信息、内存磁盘压力状态、节点监控状态等。
方法太多，那一个举例子吧setNodeDiskPressureCondition
func (kl *Kubelet) setNodeDiskPressureCondition(node *v1.Node) {currentTime := metav1.NewTime(kl.clock.Now())var condition *v1.NodeCondition// Check if NodeDiskPressure condition already exists and if it does, just pick it up for update.for i := range node.Status.Conditions {if node.Status.Conditions[i].Type == v1.NodeDiskPressure {condition = &node.Status.Conditions[i]}}newCondition := false// If the NodeDiskPressure condition doesn't exist, create oneif condition == nil {condition = &v1.NodeCondition{Type: v1.NodeDiskPressure,Status: v1.ConditionUnknown,}// cannot be appended to node.Status.Conditions here because it gets// copied to the slice. So if we append to the slice here none of the// updates we make below are reflected in the slice.newCondition = true}// Update the heartbeat timecondition.LastHeartbeatTime = currentTime// Note: The conditions below take care of the case when a new NodeDiskPressure condition is// created and as well as the case when the condition already exists. When a new condition// is created its status is set to v1.ConditionUnknown which matches either// condition.Status != v1.ConditionTrue or// condition.Status != v1.ConditionFalse in the conditions below depending on whether// the kubelet is under disk pressure or not.if kl.evictionManager.IsUnderDiskPressure() {if condition.Status != v1.ConditionTrue {condition.Status = v1.ConditionTruecondition.Reason = "KubeletHasDiskPressure"condition.Message = "kubelet has disk pressure"condition.LastTransitionTime = currentTimekl.recordNodeStatusEvent(v1.EventTypeNormal, "NodeHasDiskPressure")}} else {if condition.Status != v1.ConditionFalse {condition.Status = v1.ConditionFalsecondition.Reason = "KubeletHasNoDiskPressure"condition.Message = "kubelet has no disk pressure"condition.LastTransitionTime = currentTimekl.recordNodeStatusEvent(v1.EventTypeNormal, "NodeHasNoDiskPressure")}}if newCondition {node.Status.Conditions = append(node.Status.Conditions, *condition)}
}方法很简单，核心就是IsUnderDiskPressure，如果是存在压力就把状态改成true，否则改为false。
看完上报的方法，那这个方法是什么是被调用的呢？本能就可以想到，一个是初始一个是定时的更新，下面看看具体是不是这样的，先看初始pkg/kubelet/kubelet_node_status.go里面的initialNode方法
kl.setNodeStatus(node)这个方法就是调用刚才上面一系列收集状态的函数
func (kl *Kubelet) setNodeStatus(node *v1.Node) {for _, f := range kl.setNodeStatusFuncs {if err := f(node); err != nil {glog.Warningf("Failed to set some node status fields: %s", err)}}
}然后就是定时上报，pkg/kubelet/kubelet_node_status.go里面tryUpdateNodeStatus方法，它是定时上报master的方法。
kl.setNodeStatus(node)它同样调用setNodeStatus这个方法。顺便在多说一句，这个定时上报的方法什么时候被定时执行呢，答案在pkg/kubelet/kubelet.go的Run里面
if kl.kubeClient != nil {// Start syncing node status immediately, this may set up things the runtime needs to run.go wait.Until(kl.syncNodeStatus, kl.nodeStatusUpdateFrequency, wait.NeverStop)}通过nodeStatusUpdateFrequency指定上报周期，好了关于资源上报的代码很简单，就不赘述了。
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