Kubelet v1.25.x源码——CheckpointManager

1. 环境说明

Kubernetes源码版本：remotes/origin/release-1.25
Kubernetes编译出来的Kubelet版本：Kubernetes v1.24.0-beta.0.2463+ee7799bab469d7
Kubernetes集群实验环境：使用Kubernetes v1.25.4二进制的方式搭建了一个单节点集群

K8S 单节点单节点搭建可以参考：Kubernetes v1.25 搭建单节点集群用于Debug K8S源码

Golang版本：go1.19.3 linux/amd64
IDEA版本：2022.2.3
Delve版本：1.9.1

[root@k8s-master1 kubernetes]#
[root@k8s-master1 kubernetes]# dlv version
Delve Debugger
Version: 1.9.1
Build: $Id: d81b9fd12bfa603f3cf7a4bc842398bd61c42940 $
[root@k8s-master1 kubernetes]#
[root@k8s-master1 kubernetes]# go version
go version go1.19.3 linux/amd64
[root@k8s-master1 kubernetes]#
[root@k8s-master1 kubernetes]# kubectl version
WARNING: This version information is deprecated and will be replaced with the output from kubectl version --short.  Use --output=yaml|json to get the full version.
Client Version: version.Info{Major:"1", Minor:"25", GitVersion:"v1.25.4", GitCommit:"872a965c6c6526caa949f0c6ac028ef7aff3fb78", GitTreeState:"clean", BuildDate:"2022-11-09T13:36:36Z", GoVersion:"go1.19.3", Compiler:"gc", Platform:"linux/amd64"}
Kustomize Version: v4.5.7
Server Version: version.Info{Major:"1", Minor:"25", GitVersion:"v1.25.4", GitCommit:"872a965c6c6526caa949f0c6ac028ef7aff3fb78", GitTreeState:"clean", BuildDate:"2022-11-09T13:29:58Z", GoVersion:"go1.19.3", Compiler:"gc", Platform:"linux/amd64"}
[root@k8s-master1 kubernetes]#
[root@k8s-master1 kubernetes]#
[root@k8s-master1 kubernetes]# kubectl get nodes -owide
NAME          STATUS   ROLES    AGE   VERSION   INTERNAL-IP     EXTERNAL-IP   OS-IMAGE                KERNEL-VERSION                CONTAINER-RUNTIME
k8s-master1   Ready    <none>   31h   v1.25.4   192.168.11.71   <none>        CentOS Linux 7 (Core)   3.10.0-1160.80.1.el7.x86_64   containerd://1.6.10
[root@k8s-master1 kubernetes]#
[root@k8s-master1 kubernetes]#
[root@k8s-master1 kubernetes]# kubectl get componentstatus
Warning: v1 ComponentStatus is deprecated in v1.19+
NAME                 STATUS    MESSAGE                         ERROR
etcd-0               Healthy   {"health":"true","reason":""}
controller-manager   Healthy   ok
scheduler            Healthy   ok
[root@k8s-master1 kubernetes]#

Kubelet启动参数配置如下：

[root@k8s-master1 kubernetes]# ps -ef|grep "/usr/local/bin/kubelet"
root       7972      1  6 07:06 ?        00:00:06 /usr/local/bin/kubelet --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.kubeconfig --kubeconfig=/etc/kubernetes/kubelet.kubeconfig --config=/etc/kubernetes/kubelet-conf.yml --container-runtime-endpoint=unix:///run/containerd/containerd.sock --node-labels=node.kubernetes.io/node= --v=8
root       9549   6424  0 07:07 pts/0    00:00:00 grep --color=auto /usr/local/bin/kubelet
[root@k8s-master1 kubernetes]#

Kubelet参数配置如下：

apiVersion: kubelet.config.k8s.io/v1beta1
kind: KubeletConfiguration
address: 0.0.0.0
port: 10250
readOnlyPort: 10255
authentication:
  anonymous:
    enabled: false
  webhook:
    cacheTTL: 2m0s
    enabled: true
  x509:
    clientCAFile: /etc/kubernetes/pki/ca.pem
authorization:
  mode: Webhook
  webhook:
    cacheAuthorizedTTL: 5m0s
    cacheUnauthorizedTTL: 30s
cgroupDriver: systemd
cgroupsPerQOS: true
clusterDNS:
- 10.96.0.10
clusterDomain: cluster.local
containerLogMaxFiles: 5
containerLogMaxSize: 10Mi
contentType: application/vnd.kubernetes.protobuf
cpuCFSQuota: true
cpuManagerPolicy: none
cpuManagerReconcilePeriod: 10s
enableControllerAttachDetach: true
enableDebuggingHandlers: true
enforceNodeAllocatable:
- pods
eventBurst: 10
eventRecordQPS: 5
evictionHard:
  imagefs.available: 15%
  memory.available: 100Mi
  nodefs.available: 10%
  nodefs.inodesFree: 5%
evictionPressureTransitionPeriod: 5m0s
failSwapOn: true
fileCheckFrequency: 20s
hairpinMode: promiscuous-bridge
healthzBindAddress: 127.0.0.1
healthzPort: 10248
httpCheckFrequency: 20s
imageGCHighThresholdPercent: 85
imageGCLowThresholdPercent: 80
imageMinimumGCAge: 2m0s
iptablesDropBit: 15
iptablesMasqueradeBit: 14
kubeAPIBurst: 10
kubeAPIQPS: 5
makeIPTablesUtilChains: true
maxOpenFiles: 1000000
maxPods: 110
nodeStatusUpdateFrequency: 10s
oomScoreAdj: -999
podPidsLimit: -1
registryBurst: 10
registryPullQPS: 5
resolvConf: /etc/resolv.conf
rotateCertificates: true
runtimeRequestTimeout: 2m0s
serializeImagePulls: true
staticPodPath: /etc/kubernetes/manifests
streamingConnectionIdleTimeout: 4h0m0s
syncFrequency: 1m0s
volumeStatsAggPeriod: 1m0s

2. 组件概览

CheckpointManager主要用于管理Checkpoint，实际上就是一个checkpoint的缓存，目前主要是通过文件的方式把checkpoing缓存起来

在Kubernetes v1.25.x版本中一共有三类Checkpoint，分别是CpuManagerCheckpoint, DeviceManagerCheckpoint, MemoryManagerCheckpoint

3. 源码剖析

3.1. Checkpoint

Checkpoint

在目前v1.25版本当中，一共有三种Checkpoint的实现，分别是CpuManagerCheckpoint, DeviceManagerCheckpoing, MemoryManagerCheckpoint

type Checkpoint interface {
	MarshalCheckpoint() ([]byte, error)
	UnmarshalCheckpoint(blob []byte) error
	VerifyChecksum() error
}

3.1.1. CheckpointManager

CheckpointManager

type CheckpointManager interface {
	// 持久化检测点
	CreateCheckpoint(checkpointKey string, checkpoint Checkpoint) error

	GetCheckpoint(checkpointKey string, checkpoint Checkpoint) error

	RemoveCheckpoint(checkpointKey string) error

	ListCheckpoints() ([]string, error)
}

3.2. CreateCheckpoint

CreateCheckpoint

逻辑并不难，就是把Checkpoint序列化为文件保存起来

func (manager *impl) CreateCheckpoint(checkpointKey string, checkpoint Checkpoint) error {
	manager.mutex.Lock()
	defer manager.mutex.Unlock()
	blob, err := checkpoint.MarshalCheckpoint()
	if err != nil {
		return err
	}
	return manager.store.Write(checkpointKey, blob)
}

3.3. GetCheckpoint

GetCheckpoint

把通过CreateCheckpoint保存的checkpoint反序列化

func (manager *impl) GetCheckpoint(checkpointKey string, checkpoint Checkpoint) error {
	manager.mutex.Lock()
	defer manager.mutex.Unlock()
	blob, err := manager.store.Read(checkpointKey)
	if err != nil {
		if err == utilstore.ErrKeyNotFound {
			return errors.ErrCheckpointNotFound
		}
		return err
	}
	err = checkpoint.UnmarshalCheckpoint(blob)
	if err == nil {
		err = checkpoint.VerifyChecksum()
	}
	return err
}

3.4. RemoveCheckpoint

RemoveCheckpoint

从缓存中移除

func (manager *impl) RemoveCheckpoint(checkpointKey string) error {
	manager.mutex.Lock()
	defer manager.mutex.Unlock()
	return manager.store.Delete(checkpointKey)
}

3.5. ListCheckpoints

ListCheckpoints

获取所有的checkpoint

// ListCheckpoints returns the list of existing checkpoints.
func (manager *impl) ListCheckpoints() ([]string, error) {
	manager.mutex.Lock()
	defer manager.mutex.Unlock()
	keys, err := manager.store.List()
	if err != nil {
		return []string{}, fmt.Errorf("failed to list checkpoint store: %v", err)
	}
	return keys, nil
}