K8s核心资源对象-Pod（静态Pod）

基于1.25

什么是静态Pod

Static Pod在指定Node由kubelet守护进程之间管理，不需要kube-apiserver监管。

• kubelete监视每个static Pod（失败之后重启）
• static Pod只允许在某一个节点上
• 节点上运行Pod ，API Server是可见的，但是不受到kube-apiserver控制

创建静态Pod

有俩种模式：配置文件和HTTP

• 配置文件：定义标准的Pod，用JSON或者YAML格式存储在指定目录
  • 使用kubelet的”staticPodPath:“
  • kubelet定期扫描目录，实现Pod 的CRUD
  • 扫描忽略已点号开头的文件

静态Pod的创建流程

有三种func：

• NewSourceFile
• NewSourceURL
• NewSourceApiserver

最终通过m.merger.Merge最终合并

• Ref:https://github.com/kubernetes/kubernetes/blob/88e994f6bf8fc88114c5b733e09afea339bea66d/pkg/kubelet/kubelet.go#L252

// makePodSourceConfig creates a config.PodConfig from the given
// KubeletConfiguration or returns an error.
func makePodSourceConfig(kubeCfg *kubeletconfiginternal.KubeletConfiguration, kubeDeps *Dependencies, nodeName types.NodeName, nodeHasSynced func() bool) (*config.PodConfig, error) {
	manifestURLHeader := make(http.Header)
	if len(kubeCfg.StaticPodURLHeader) > 0 {
		for k, v := range kubeCfg.StaticPodURLHeader {
			for i := range v {
				manifestURLHeader.Add(k, v[i])
			}
		}
	}

	// source of all configuration
  // 创建一个PodConfig对象，最终汇总三种Pod来源
	cfg := config.NewPodConfig(config.PodConfigNotificationIncremental, kubeDeps.Recorder)

	// TODO:  it needs to be replaced by a proper context in the future
	ctx := context.TODO()

	// define file config source
	if kubeCfg.StaticPodPath != "" {
		klog.InfoS("Adding static pod path", "path", kubeCfg.StaticPodPath)
		config.NewSourceFile(kubeCfg.StaticPodPath, nodeName, kubeCfg.FileCheckFrequency.Duration, cfg.Channel(ctx, kubetypes.FileSource))
	}

	// define url config source
	if kubeCfg.StaticPodURL != "" {
		klog.InfoS("Adding pod URL with HTTP header", "URL", kubeCfg.StaticPodURL, "header", manifestURLHeader)
		config.NewSourceURL(kubeCfg.StaticPodURL, manifestURLHeader, nodeName, kubeCfg.HTTPCheckFrequency.Duration, cfg.Channel(ctx, kubetypes.HTTPSource))
	}

	if kubeDeps.KubeClient != nil {
		klog.InfoS("Adding apiserver pod source")
		config.NewSourceApiserver(kubeDeps.KubeClient, nodeName, nodeHasSynced, cfg.Channel(ctx, kubetypes.ApiserverSource))
	}
	return cfg, nil
}

• Ref：https://github.com/kubernetes/kubernetes/blob/88e994f6bf8fc88114c5b733e09afea339bea66d/cmd/kubelet/app/server.go#L1180

func startKubelet(k kubelet.Bootstrap, podCfg *config.PodConfig, kubeCfg *kubeletconfiginternal.KubeletConfiguration, kubeDeps *kubelet.Dependencies, enableServer bool) {
	// start the kubelet
  // 消费静态Pod
	go k.Run(podCfg.Updates())

	// start the kubelet server
	if enableServer {
		go k.ListenAndServe(kubeCfg, kubeDeps.TLSOptions, kubeDeps.Auth, kubeDeps.TracerProvider)
	}
	if kubeCfg.ReadOnlyPort > 0 {
		go k.ListenAndServeReadOnly(netutils.ParseIPSloppy(kubeCfg.Address), uint(kubeCfg.ReadOnlyPort))
	}
	if utilfeature.DefaultFeatureGate.Enabled(features.KubeletPodResources) {
		go k.ListenAndServePodResources()
	}
}