一文读懂 SuperEdge 分布式健康检查 (边端)
前言
SuperEdge 介绍
SuperEdge 分布式健康检查
边缘计算场景下,边缘节点与云端的网络环境十分复杂,连接并不可靠,在原生 Kubernetes 集群中,会造成 apiserver 和节点连接的中断,节点状态的异常,最终导致pod的驱逐和 endpoint 的缺失,造成服务的中断和波动,具体来说原生 Kubernetes 处理如下:
失联的节点被置为 ConditionUnknown 状态,并被添加 NoSchedule 和 NoExecute 的 taints 失联的节点上的 pod 被驱逐,并在其他节点上进行重建 失联的节点上的 pod 从 Service 的 Endpoint 列表中移除
因此,边缘计算场景仅仅依赖边端和 apiserver 的连接情况是不足以判断节点是否异常的,会因为网络的不可靠造成误判,影响正常服务。而相较于云端和边缘端的连接,显然边端节点之间的连接更为稳定,具有更高的参考价值,因此 superedge 提出了边缘分布式健康检查机制。该机制中节点状态判定除了要考虑 apiserver 的因素外,还引入了节点的评估因素,进而对节点进行更为全面的状态判断。通过这个功能,能够避免由于云边网络不可靠造成的大量的 pod 迁移和重建,保证服务的稳定
具体来说,主要通过如下三个层面增强节点状态判断的准确性:
每个节点定期探测其他节点健康状态 集群内所有节点定期投票决定各节点的状态 云端和边端节点共同决定节点状态
而分布式健康检查最终的判断处理如下:
edge-health-daemon 源码分析
在深入源码之前先介绍一下分布式健康检查的实现原理,其架构图如下所示:
Kubernetes 每个 node 在 kube-node-lease namespace 下会对应一个 Lease object,kubelet 每隔 node-status-update-frequency 时间(默认10s)会更新对应node的 Lease object。
node-controller 会每隔 node-monitor-period 时间(默认5s)检查 Lease object 是否更新,如果超过 node-monitor-grace-period 时间(默认40s)没有发生过更新,则认为这个 node 不健康,会更新 NodeStatus(ConditionUnknown)
spec:
...
taints:
- effect: NoSchedule
key: node.kubernetes.io/unreachable
timeAdded: "2020-07-02T03:50:47Z"
- effect: NoExecute
key: node.kubernetes.io/unreachable
timeAdded: "2020-07-02T03:50:53Z"
对于打上 NoSchedule taint 的母机,Scheduler 不会调度新的负载在该 node 上了;而对于打上 NoExecute(node.kubernetes.io/unreachable) taint 的母机,node controller 会在节点心跳超时之后一段时间(默认5mins)驱逐该节点上的 pod。
分布式健康检查边端的 edge-health-daemon 组件会对同区域边缘节点执行分布式健康检查,并向 apiserver 发送健康状态投票结果(给 node 打 annotation)。
此外,为了实现在云边断连且分布式健康检查状态正常的情况下:
失联的节点上的 pod 不会从 Service 的 Endpoint 列表中移除 失联的节点上的 pod 不会被驱逐
还需要在云端运行 edge-health-admission(Kubernetes mutating admission webhook[1]),不断根据 node edge-health annotation 调整 kube-controller-manager 设置的 node taint(去掉NoExecute taint)以及 endpoints (将失联节点上的 pods 从 endpoint subsets notReadyAddresses 移到 addresses中),从而实现云端和边端共同决定节点状态。
type EdgeHealthMetadata struct {
*NodeMetadata
*CheckMetadata
}
type NodeMetadata struct {
NodeList []v1.Node
sync.RWMutex
}
type CheckMetadata struct {
CheckInfo map[string]map[string]CheckDetail // Checker ip:{Checked ip:Check detail}
CheckPluginScoreInfo map[string]map[string]float64 // Checked ip:{Plugin name:Check score}
sync.RWMutex
}
type CheckDetail struct {
Normal bool
Time time.Time
}
type CommunInfo struct {
SourceIP string // ClientIP,Checker ip
CheckDetail map[string]CheckDetail // Checked ip:Check detail
Hmac string
}
含义如下:
NodeMetadata:为了实现分区域分布式健康检查机制而维护的边缘节点 cache,其中包含该区域内的所有边缘节点列表 NodeList CheckMetadata:存放健康检查的结果,具体来说包括两个数据结构: CheckPluginScoreInfo:为 Checked ip:{Plugin name:Check score}
组织形式。第一级 key 表示:被检查的ip;第二级 key 表示:检查插件的名称;value 表示:检查分数CheckInfo:为 Checker ip:{Checked ip:Check detail}
组织形式。第一级key表示:执行检查的ip;第二级key表示:被检查的ip;value表示检查结果 CheckDetailCheckDetail:代表健康检查的结果 Normal:Normal 为 true 表示检查结果正常;false 表示异常 Time:表示得出该结果时的时间,用于结果有效性的判断(超过一段时间没有更新的结果将无效) CommunInfo:边缘节点向其它节点发送健康检查结果时使用的数据,其中包括: SourceIP:表示执行检查的ip CheckDetail:为 Checked ip:Check detail
组织形式,包含被检查的ip以及检查结果Hmac:SourceIP 以及 CheckDetail 进行 hmac 得到,用于边缘节点通信过程中判断传输数据的有效性(是否被篡改)
edge-health-daemon 主体逻辑包括四部分功能:
SyncNodeList:根据边缘节点所在的 zone 刷新 node cache,同时更新 CheckMetadata相关数据 ExecuteCheck:对每个边缘节点执行若干种类的健康检查插件(ping,kubelet等),并将各插件检查分数汇总,根据用户设置的基准线得出节点是否健康的结果 Commun:将本节点对其它各节点健康检查的结果发送给其它节点 Vote:对所有节点健康检查的结果分类,如果某个节点被大多数(>1/2)节点判定为正常,则对该节点添加 superedgehealth/node-health:true
annotation,表明该节点分布式健康检查结果为正常;否则,对该节点添加superedgehealth/node-health:false
annotation,表明该节点分布式健康检查结果为异常
下面依次对上述功能进行源码分析:
1、SyncNodeList
SyncNodeList 每隔 HealthCheckPeriod 秒 (health-check-period 选项)执行一次,会按照如下情况分类刷新 node cache:
如果 kube-system namespace 下不存在名为 edge-health-zone-config的configmap,则没有开启多地域探测,因此会获取所有边缘节点列表并刷新 node cache 否则,如果 edge-health-zone-config 的 configmap 数据部分 TaintZoneAdmission 为 false,则没有开启多地域探测,因此会获取所有边缘节点列表并刷新 node cache 如果 TaintZoneAdmission 为 true,且 node 有"superedgehealth/topology-zone"标签(标示区域),则获取"superedgehealth/topology-zone" label value 相同的节点列表并刷新 node cache 如果 node 没有"superedgehealth/topology-zone" label,则只会将边缘节点本身添加到分布式健康检查节点列表中并刷新 node cache(only itself)
func (ehd *EdgeHealthDaemon) SyncNodeList() {
// Only sync nodes when self-located found
var host *v1.Node
if host = ehd.metadata.GetNodeByName(ehd.cfg.Node.HostName); host == nil {
klog.Errorf("Self-hostname %s not found", ehd.cfg.Node.HostName)
return
}
// Filter cloud nodes and retain edge ones
masterRequirement, err := labels.NewRequirement(common.MasterLabel, selection.DoesNotExist, []string{})
if err != nil {
klog.Errorf("New masterRequirement failed %+v", err)
return
}
masterSelector := labels.NewSelector()
masterSelector = masterSelector.Add(*masterRequirement)
if mrc, err := ehd.cmLister.ConfigMaps(metav1.NamespaceSystem).Get(common.TaintZoneConfigMap); err != nil {
if apierrors.IsNotFound(err) { // multi-region configmap not found
if NodeList, err := ehd.nodeLister.List(masterSelector); err != nil {
klog.Errorf("Multi-region configmap not found and get nodes err %+v", err)
return
} else {
ehd.metadata.SetByNodeList(NodeList)
}
} else {
klog.Errorf("Get multi-region configmap err %+v", err)
return
}
} else { // multi-region configmap found
mrcv := mrc.Data[common.TaintZoneConfigMapKey]
klog.V(4).Infof("Multi-region value is %s", mrcv)
if mrcv == "false" { // close multi-region check
if NodeList, err := ehd.nodeLister.List(masterSelector); err != nil {
klog.Errorf("Multi-region configmap exist but disabled and get nodes err %+v", err)
return
} else {
ehd.metadata.SetByNodeList(NodeList)
}
} else { // open multi-region check
if hostZone, existed := host.Labels[common.TopologyZone]; existed {
klog.V(4).Infof("Host %s has HostZone %s", host.Name, hostZone)
zoneRequirement, err := labels.NewRequirement(common.TopologyZone, selection.Equals, []string{hostZone})
if err != nil {
klog.Errorf("New masterZoneRequirement failed: %+v", err)
return
}
masterZoneSelector := labels.NewSelector()
masterZoneSelector = masterZoneSelector.Add(*masterRequirement, *zoneRequirement)
if nodeList, err := ehd.nodeLister.List(masterZoneSelector); err != nil {
klog.Errorf("TopologyZone label for hostname %s but get nodes err: %+v", host.Name, err)
return
} else {
ehd.metadata.SetByNodeList(nodeList)
}
} else { // Only check itself if there is no TopologyZone label
klog.V(4).Infof("Only check itself since there is no TopologyZone label for hostname %s", host.Name)
ehd.metadata.SetByNodeList([]*v1.Node{host})
}
}
}
// Init check plugin score
ipList := make(map[string]struct{})
for _, node := range ehd.metadata.Copy() {
for _, addr := range node.Status.Addresses {
if addr.Type == v1.NodeInternalIP {
ipList[addr.Address] = struct{}{}
ehd.metadata.InitCheckPluginScore(addr.Address)
}
}
}
// Delete redundant check plugin score
for _, checkedIp := range ehd.metadata.CopyCheckedIp() {
if _, existed := ipList[checkedIp]; !existed {
ehd.metadata.DeleteCheckPluginScore(checkedIp)
}
}
// Delete redundant check info
for checkerIp := range ehd.metadata.CopyAll() {
if _, existed := ipList[checkerIp]; !existed {
ehd.metadata.DeleteByIp(ehd.cfg.Node.LocalIp, checkerIp)
}
}
klog.V(4).Infof("SyncNodeList check info %+v successfully", ehd.metadata)
}
...
func (cm *CheckMetadata) DeleteByIp(localIp, ip string) {
cm.Lock()
defer cm.Unlock()
delete(cm.CheckInfo[localIp], ip)
delete(cm.CheckInfo, ip)
}
Checked ip
:被检查的ip)。另外,会删除 CheckMetadata.CheckPluginScoreInfo 以及 CheckMetadata.CheckInfo中多余的items(不属于该边缘节点检查范围)。
2、ExecuteCheck
func (ehd *EdgeHealthDaemon) ExecuteCheck() {
util.ParallelizeUntil(context.TODO(), 16, len(ehd.checkPlugin.Plugins), func(index int) {
ehd.checkPlugin.Plugins[index].CheckExecute(ehd.metadata.CheckMetadata)
})
klog.V(4).Infof("CheckPluginScoreInfo is %+v after health check", ehd.metadata.CheckPluginScoreInfo)
for checkedIp, pluginScores := range ehd.metadata.CopyCheckPluginScore() {
totalScore := 0.0
for _, score := range pluginScores {
totalScore += score
}
if totalScore >= ehd.cfg.Check.HealthCheckScoreLine {
ehd.metadata.SetByCheckDetail(ehd.cfg.Node.LocalIp, checkedIp, metadata.CheckDetail{Normal: true})
} else {
ehd.metadata.SetByCheckDetail(ehd.cfg.Node.LocalIp, checkedIp, metadata.CheckDetail{Normal: false})
}
}
klog.V(4).Infof("CheckInfo is %+v after health check", ehd.metadata.CheckInfo)
}
这里会调用 ParallelizeUntil 并发执行各检查插件,edge-health 目前支持 ping 以及 kubelet 两种检查插件,在 checkplugin 目录(github.com/superedge/superedge/pkg/edge-health/checkplugin),通过 Register 注册到 PluginInfo 单例(plugin列表)中,如下:
// TODO: handle flag parse errors
func (pcp *PingCheckPlugin) Set(s string) error {
var err error
for _, para := range strings.Split(s, ",") {
if len(para) == 0 {
continue
}
arr := strings.Split(para, "=")
trimKey := strings.TrimSpace(arr[0])
switch trimKey {
case "timeout":
timeout, _ := strconv.Atoi(strings.TrimSpace(arr[1]))
pcp.HealthCheckoutTimeOut = timeout
case "retries":
retries, _ := strconv.Atoi(strings.TrimSpace(arr[1]))
pcp.HealthCheckRetries = retries
case "weight":
weight, _ := strconv.ParseFloat(strings.TrimSpace(arr[1]), 64)
pcp.Weight = weight
case "port":
port, _ := strconv.Atoi(strings.TrimSpace(arr[1]))
pcp.Port = port
}
}
PluginInfo = NewPlugin()
PluginInfo.Register(pcp)
return err
}
func (p *Plugin) Register(plugin CheckPlugin) {
p.Plugins = append(p.Plugins, plugin)
klog.V(4).Info("Register check plugin: %+v", plugin)
}
...
var (
PluginOnce sync.Once
PluginInfo Plugin
)
type Plugin struct {
Plugins []CheckPlugin
}
func NewPlugin() Plugin {
PluginOnce.Do(func() {
PluginInfo = Plugin{
Plugins: []CheckPlugin{},
}
})
return PluginInfo
}
每种插件具体执行健康检查的逻辑封装在 CheckExecute 中,这里以 ping plugin 为例:
// github.com/superedge/superedge/pkg/edge-health/checkplugin/pingcheck.go
func (pcp *PingCheckPlugin) CheckExecute(checkMetadata *metadata.CheckMetadata) {
copyCheckedIp := checkMetadata.CopyCheckedIp()
util.ParallelizeUntil(context.TODO(), 16, len(copyCheckedIp), func(index int) {
checkedIp := copyCheckedIp[index]
var err error
for i := 0; i < pcp.HealthCheckRetries; i++ {
if _, err := net.DialTimeout("tcp", checkedIp+":"+strconv.Itoa(pcp.Port), time.Duration(pcp.HealthCheckoutTimeOut)*time.Second); err == nil {
break
}
}
if err == nil {
klog.V(4).Infof("Edge ping health check plugin %s for ip %s succeed", pcp.Name(), checkedIp)
checkMetadata.SetByPluginScore(checkedIp, pcp.Name(), pcp.GetWeight(), common.CheckScoreMax)
} else {
klog.Warning("Edge ping health check plugin %s for ip %s failed, possible reason %s", pcp.Name(), checkedIp, err.Error())
checkMetadata.SetByPluginScore(checkedIp, pcp.Name(), pcp.GetWeight(), common.CheckScoreMin)
}
})
}
// CheckPluginScoreInfo relevant functions
func (cm *CheckMetadata) SetByPluginScore(checkedIp, pluginName string, weight float64, score int) {
cm.Lock()
defer cm.Unlock()
if _, existed := cm.CheckPluginScoreInfo[checkedIp]; !existed {
cm.CheckPluginScoreInfo[checkedIp] = make(map[string]float64)
}
cm.CheckPluginScoreInfo[checkedIp][pluginName] = float64(score) * weight
}
CheckExecute 会对同区域每个节点执行 ping 探测(net.DialTimeout),如果失败,则给该节点打 CheckScoreMin 分(0);否则,打 CheckScoreMax 分(100)
每种检查插件会有一个 Weight 参数,表示了该检查插件分数的权重值,所有权重参数之和应该为1,对应基准分数线 HealthCheckScoreLine 范围0-100。因此这里在设置分数时,会乘以权重。
func (ehd *EdgeHealthDaemon) ExecuteCheck() {
util.ParallelizeUntil(context.TODO(), 16, len(ehd.checkPlugin.Plugins), func(index int) {
ehd.checkPlugin.Plugins[index].CheckExecute(ehd.metadata.CheckMetadata)
})
klog.V(4).Infof("CheckPluginScoreInfo is %+v after health check", ehd.metadata.CheckPluginScoreInfo)
for checkedIp, pluginScores := range ehd.metadata.CopyCheckPluginScore() {
totalScore := 0.0
for _, score := range pluginScores {
totalScore += score
}
if totalScore >= ehd.cfg.Check.HealthCheckScoreLine {
ehd.metadata.SetByCheckDetail(ehd.cfg.Node.LocalIp, checkedIp, metadata.CheckDetail{Normal: true})
} else {
ehd.metadata.SetByCheckDetail(ehd.cfg.Node.LocalIp, checkedIp, metadata.CheckDetail{Normal: false})
}
}
klog.V(4).Infof("CheckInfo is %+v after health check", ehd.metadata.CheckInfo)
}
func (ehd *EdgeHealthDaemon) Run(stopCh <-chan struct{}) {
// Execute edge health prepare and check
ehd.PrepareAndCheck(stopCh)
// Execute vote
vote := vote.NewVoteEdge(&ehd.cfg.Vote)
go vote.Vote(ehd.metadata, ehd.cfg.Kubeclient, ehd.cfg.Node.LocalIp, stopCh)
// Execute communication
communEdge := commun.NewCommunEdge(&ehd.cfg.Commun)
communEdge.Commun(ehd.metadata.CheckMetadata, ehd.cmLister, ehd.cfg.Node.LocalIp, stopCh)
<-stopCh
}
既然是互相传递结果给其它节点,则必然会有接受和发送模块:
func (c *CommunEdge) Commun(checkMetadata *metadata.CheckMetadata, cmLister corelisters.ConfigMapLister, localIp string, stopCh <-chan struct{}) {
go c.communReceive(checkMetadata, cmLister, stopCh)
wait.Until(func() {
c.communSend(checkMetadata, cmLister, localIp)
}, time.Duration(c.CommunPeriod)*time.Second, stopCh)
}
其中 communSend 负责向其它节点发送本节点对它们的检查结果;而 communReceive 负责接受其它边缘节点的检查结果。下面依次分析:
func (c *CommunEdge) communSend(checkMetadata *metadata.CheckMetadata, cmLister corelisters.ConfigMapLister, localIp string) {
copyLocalCheckDetail := checkMetadata.CopyLocal(localIp)
var checkedIps []string
for checkedIp := range copyLocalCheckDetail {
checkedIps = append(checkedIps, checkedIp)
}
util.ParallelizeUntil(context.TODO(), 16, len(checkedIps), func(index int) {
// Only send commun information to other edge nodes(excluding itself)
dstIp := checkedIps[index]
if dstIp == localIp {
return
}
// Send commun information
communInfo := metadata.CommunInfo{SourceIP: localIp, CheckDetail: copyLocalCheckDetail}
if hmac, err := util.GenerateHmac(communInfo, cmLister); err != nil {
log.Errorf("communSend: generateHmac err %+v", err)
return
} else {
communInfo.Hmac = hmac
}
commonInfoBytes, err := json.Marshal(communInfo)
if err != nil {
log.Errorf("communSend: json.Marshal commun info err %+v", err)
return
}
commonInfoReader := bytes.NewReader(commonInfoBytes)
for i := 0; i < c.CommunRetries; i++ {
req, err := http.NewRequest("PUT", "http://"+dstIp+":"+strconv.Itoa(c.CommunServerPort)+"/result", commonInfoReader)
if err != nil {
log.Errorf("communSend: NewRequest for remote edge node %s err %+v", dstIp, err)
continue
}
if err = util.DoRequestAndDiscard(c.client, req); err != nil {
log.Errorf("communSend: DoRequestAndDiscard for remote edge node %s err %+v", dstIp, err)
} else {
log.V(4).Infof("communSend: put commun info %+v to remote edge node %s successfully", communInfo, dstIp)
break
}
}
})
}
构建 CommunInfo 结构体,包括: SourceIP:表示执行检查的ip CheckDetail:为 Checked ip:Check detail 组织形式,包含被检查的ip以及检查结果 调用 GenerateHmac 构建 Hmac:实际上是以 kube-system 下的 hmac-config configmap hmackey 字段为 key,对 SourceIP 以及 CheckDetail进行 hmac 得到,用于判断传输数据的有效性(是否被篡改)
func GenerateHmac(communInfo metadata.CommunInfo, cmLister corelisters.ConfigMapLister) (string, error) {
addrBytes, err := json.Marshal(communInfo.SourceIP)
if err != nil {
return "", err
}
detailBytes, _ := json.Marshal(communInfo.CheckDetail)
if err != nil {
return "", err
}
hmacBefore := string(addrBytes) + string(detailBytes)
if hmacConf, err := cmLister.ConfigMaps(metav1.NamespaceSystem).Get(common.HmacConfig); err != nil {
return "", err
} else {
return GetHmacCode(hmacBefore, hmacConf.Data[common.HmacKey])
}
}
func GetHmacCode(s, key string) (string, error) {
h := hmac.New(sha256.New, []byte(key))
if _, err := io.WriteString(h, s); err != nil {
return "", err
}
return fmt.Sprintf("%x", h.Sum(nil)), nil
}
发送上述构建的 CommunInfo 给其它边缘节点 (DoRequestAndDiscard)
// TODO: support changeable server listen port
func (c *CommunEdge) communReceive(checkMetadata *metadata.CheckMetadata, cmLister corelisters.ConfigMapLister, stopCh <-chan struct{}) {
svr := &http.Server{Addr: ":" + strconv.Itoa(c.CommunServerPort)}
svr.ReadTimeout = time.Duration(c.CommunTimeout) * time.Second
svr.WriteTimeout = time.Duration(c.CommunTimeout) * time.Second
http.HandleFunc("/debug/flags/v", pkgutil.UpdateLogLevel)
http.HandleFunc("/result", func(w http.ResponseWriter, r *http.Request) {
var communInfo metadata.CommunInfo
if r.Body == nil {
http.Error(w, "Invalid commun information", http.StatusBadRequest)
return
}
err := json.NewDecoder(r.Body).Decode(&communInfo)
if err != nil {
http.Error(w, fmt.Sprintf("Invalid commun information %+v", err), http.StatusBadRequest)
return
}
log.V(4).Infof("Received common information from %s : %+v", communInfo.SourceIP, communInfo.CheckDetail)
if _, err := io.WriteString(w, "Received!\n"); err != nil {
log.Errorf("communReceive: send response err %+v", err)
http.Error(w, fmt.Sprintf("Send response err %+v", err), http.StatusInternalServerError)
return
}
if hmac, err := util.GenerateHmac(communInfo, cmLister); err != nil {
log.Errorf("communReceive: server GenerateHmac err %+v", err)
http.Error(w, fmt.Sprintf("GenerateHmac err %+v", err), http.StatusInternalServerError)
return
} else {
if hmac != communInfo.Hmac {
log.Errorf("communReceive: Hmac not equal, hmac is %s but received commun info hmac is %s", hmac, communInfo.Hmac)
http.Error(w, "Hmac not match", http.StatusForbidden)
return
}
}
log.V(4).Infof("communReceive: Hmac match")
checkMetadata.SetByCommunInfo(communInfo)
log.V(4).Infof("After communicate, check info is %+v", checkMetadata.CheckInfo)
})
go func() {
if err := svr.ListenAndServe(); err != http.ErrServerClosed {
log.Fatalf("Server: exit with error %+v", err)
}
}()
for {
select {
case <-stopCh:
ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
defer cancel()
if err := svr.Shutdown(ctx); err != nil {
log.Errorf("Server: program exit, server exit error %+v", err)
}
return
default:
}
}
}
通过
/result
路由接受请求,并将请求内容解析成 CommunInfo对 CommunInfo 执行 GenerateHmac 获取hmac值,并与 CommunInfo.Hmac 字段进行对比,检查接受数据的有效性
最后将 CommunInfo 检查结果写入 CheckInfo,注意:CheckDetail.Time 设置为写入时的时间
// CheckInfo relevant functions
func (cm *CheckMetadata) SetByCommunInfo(c CommunInfo) {
cm.Lock()
defer cm.Unlock()
if _, existed := cm.CheckInfo[c.SourceIP]; !existed {
cm.CheckInfo[c.SourceIP] = make(map[string]CheckDetail)
}
for k, detail := range c.CheckDetail {
// Update time to local timestamp since different machines have different ones
detail.Time = time.Now()
c.CheckDetail[k] = detail
}
cm.CheckInfo[c.SourceIP] = c.CheckDetail
}
最后在接受到 stopCh 信号时,通过 svr.Shutdown 平滑关闭服务。
4、Vote
func (v *VoteEdge) Vote(edgeHealthMetadata *metadata.EdgeHealthMetadata, kubeclient clientset.Interface,
localIp string, stopCh <-chan struct{}) {
go wait.Until(func() {
v.vote(edgeHealthMetadata, kubeclient, localIp, stopCh)
}, time.Duration(v.VotePeriod)*time.Second, stopCh)
}
首先根据检查结果统计出状态正常以及异常的节点列表:
type votePair struct {
pros int
cons int
}
...
var (
prosVoteIpList, consVoteIpList []string
// Init votePair since cannot assign to struct field voteCountMap[checkedIp].pros in map
vp votePair
)
voteCountMap := make(map[string]votePair) // {"127.0.0.1":{"pros":1,"cons":2}}
copyCheckInfo := edgeHealthMetadata.CopyAll()
// Note that voteThreshold should be calculated by checked instead of checker
// since checked represents the total valid edge health nodes while checker may contain partly ones.
voteThreshold := (edgeHealthMetadata.GetCheckedIpLen() + 1) / 2
for _, checkedDetails := range copyCheckInfo {
for checkedIp, checkedDetail := range checkedDetails {
if !time.Now().After(checkedDetail.Time.Add(time.Duration(v.VoteTimeout) * time.Second)) {
if _, existed := voteCountMap[checkedIp]; !existed {
voteCountMap[checkedIp] = votePair{0, 0}
}
vp = voteCountMap[checkedIp]
if checkedDetail.Normal {
vp.pros++
if vp.pros >= voteThreshold {
prosVoteIpList = append(prosVoteIpList, checkedIp)
}
} else {
vp.cons++
if vp.cons >= voteThreshold {
consVoteIpList = append(consVoteIpList, checkedIp)
}
}
voteCountMap[checkedIp] = vp
}
}
}
log.V(4).Infof("Vote: voteCountMap is %+v", voteCountMap)
...
其中状态判断的逻辑如下:
如果超过一半(>)的节点对该节点的检查结果为正常,则认为该节点状态正常(注意时间差在 VoteTimeout 内) 如果超过一半(>)的节点对该节点的检查结果为异常,则认为该节点状态异常(注意时间差在 VoteTimeout 内) 除开上述情况,认为节点状态判断无效,对这些节点不做任何处理(可能存在脑裂的情况)
对状态正常的节点做如下处理:
...
// Handle prosVoteIpList
util.ParallelizeUntil(context.TODO(), 16, len(prosVoteIpList), func(index int) {
if node := edgeHealthMetadata.GetNodeByAddr(prosVoteIpList[index]); node != nil {
log.V(4).Infof("Vote: vote pros to edge node %s begin ...", node.Name)
nodeCopy := node.DeepCopy()
needUpdated := false
if nodeCopy.Annotations == nil {
nodeCopy.Annotations = map[string]string{
common.NodeHealthAnnotation: common.NodeHealthAnnotationPros,
}
needUpdated = true
} else {
if healthy, existed := nodeCopy.Annotations[common.NodeHealthAnnotation]; existed {
if healthy != common.NodeHealthAnnotationPros {
nodeCopy.Annotations[common.NodeHealthAnnotation] = common.NodeHealthAnnotationPros
needUpdated = true
}
} else {
nodeCopy.Annotations[common.NodeHealthAnnotation] = common.NodeHealthAnnotationPros
needUpdated = true
}
}
if index, existed := admissionutil.TaintExistsPosition(nodeCopy.Spec.Taints, common.UnreachableNoExecuteTaint); existed {
nodeCopy.Spec.Taints = append(nodeCopy.Spec.Taints[:index], nodeCopy.Spec.Taints[index+1:]...)
needUpdated = true
}
if needUpdated {
if _, err := kubeclient.CoreV1().Nodes().Update(context.TODO(), nodeCopy, metav1.UpdateOptions{}); err != nil {
log.Errorf("Vote: update pros vote to edge node %s error %+v ", nodeCopy.Name, err)
} else {
log.V(2).Infof("Vote: update pros vote to edge node %s successfully", nodeCopy.Name)
}
}
} else {
log.Warningf("Vote: edge node addr %s not found", prosVoteIpList[index])
}
})
...
添加或者更新"superedgehealth/node-health" annotation 值为"true",表明分布式健康检查判断该节点状态正常。
如果node存在 NoExecute(node.kubernetes.io/unreachable) taint,则将其去掉,并更新 node.
// Handle consVoteIpList
util.ParallelizeUntil(context.TODO(), 16, len(consVoteIpList), func(index int) {
if node := edgeHealthMetadata.GetNodeByAddr(consVoteIpList[index]); node != nil {
log.V(4).Infof("Vote: vote cons to edge node %s begin ...", node.Name)
nodeCopy := node.DeepCopy()
needUpdated := false
if nodeCopy.Annotations == nil {
nodeCopy.Annotations = map[string]string{
common.NodeHealthAnnotation: common.NodeHealthAnnotationCons,
}
needUpdated = true
} else {
if healthy, existed := nodeCopy.Annotations[common.NodeHealthAnnotation]; existed {
if healthy != common.NodeHealthAnnotationCons {
nodeCopy.Annotations[common.NodeHealthAnnotation] = common.NodeHealthAnnotationCons
needUpdated = true
}
} else {
nodeCopy.Annotations[common.NodeHealthAnnotation] = common.NodeHealthAnnotationCons
needUpdated = true
}
}
if needUpdated {
if _, err := kubeclient.CoreV1().Nodes().Update(context.TODO(), nodeCopy, metav1.UpdateOptions{}); err != nil {
log.Errorf("Vote: update cons vote to edge node %s error %+v ", nodeCopy.Name, err)
} else {
log.V(2).Infof("Vote: update cons vote to edge node %s successfully", nodeCopy.Name)
}
}
} else {
log.Warningf("Vote: edge node addr %s not found", consVoteIpList[index])
}
})
失联的节点上的 pod 不会从 Service 的 Endpoint 列表中移除 失联的节点上的 pod 不会被驱逐
总结
分布式健康检查对于云边断连情况的处理区别原生Kubernetes如下:
原生Kubernetes:
失联的节点被置为ConditionUnknown状态,并被添加NoSchedule和NoExecute的taints 失联的节点上的pod被驱逐,并在其他节点上进行重建 失联的节点上的pod从Service的Endpoint列表中移除
分布式健康检查:
分布式健康检查主要通过如下三个层面增强节点状态判断的准确性: 每个节点定期探测其他节点健康状态 集群内所有节点定期投票决定各节点的状态 云端和边端节点共同决定节点状态 分布式健康检查功能由边端的edge-health-daemon以及云端的edge-health-admission组成,功能分别如下:
edge-health-daemon:对同区域边缘节点执行分布式健康检查,并向apiserver发送健康状态投票结果(给node打annotation),主体逻辑包括四部分功能:
SyncNodeList:根据边缘节点所在的zone刷新node cache,同时更新CheckMetadata相关数据 ExecuteCheck:对每个边缘节点执行若干种类的健康检查插件(ping,kubelet等),并将各插件检查分数汇总,根据用户设置的基准线得出节点是否健康的结果 Commun:将本节点对其它各节点健康检查的结果发送给其它节点 Vote:对所有节点健康检查的结果分类,如果某个节点被大多数(>1/2)节点判定为正常,则对该节点添加superedgehealth/node-health:true annotation,表明该节点分布式健康检查结果为正常;否则,对该节点添加superedgehealth/node-health:false annotation,表明该节点分布式健康检查结果为异常。
edge-health-admission(Kubernetes mutating admission webhook):不断根据node edge-health annotation调整kube-controller-manager设置的node taint(去掉NoExecute taint)以及endpoints(将失联节点上的pods从endpoint subsets notReadyAddresses移到addresses中),从而实现云端和边端共同决定节点状态。
如果您同样关注 SuperEdge 开源项目,可以扫描下面的二维码加入我们的交流群,一起探讨。
参考资料:
[1] Kubernetes mutating admission webhook:
【https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/#mutatingadmissionwebhook】
[2] duyanghao kubernetes-reading-notes: 【https://github.com/duyanghao/kubernetes-reading-notes/blob/master/superedge/edge-health/README.md】[3] github地址:【https://github.com/superedge/superedge】
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