kubelet gc源码分析

本文主要是介绍kubelet gc源码分析，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

kubelet是负载干活的组件，它会定期的清理多余死掉的容器和镜像，这篇blog基于kubernetes1.7.6的代码，关于gc的深入源码分析
好了，先看gc是随着kubelet启动而启动的pkg/kubelet/kubelet.go，

func (kl *Kubelet) StartGarbageCollection() {loggedContainerGCFailure := falsego wait.Until(func() {if err := kl.containerGC.GarbageCollect(); err != nil {glog.Errorf("Container garbage collection failed: %v", err)kl.recorder.Eventf(kl.nodeRef, v1.EventTypeWarning, events.ContainerGCFailed, err.Error())loggedContainerGCFailure = true} else {var vLevel glog.Level = 4if loggedContainerGCFailure {vLevel = 1loggedContainerGCFailure = false}glog.V(vLevel).Infof("Container garbage collection succeeded")}}, ContainerGCPeriod, wait.NeverStop)prevImageGCFailed := falsego wait.Until(func() {if err := kl.imageManager.GarbageCollect(); err != nil {if prevImageGCFailed {glog.Errorf("Image garbage collection failed multiple times in a row: %v", err)// Only create an event for repeated failureskl.recorder.Eventf(kl.nodeRef, v1.EventTypeWarning, events.ImageGCFailed, err.Error())} else {glog.Errorf("Image garbage collection failed once. Stats initialization may not have completed yet: %v", err)}prevImageGCFailed = true} else {var vLevel glog.Level = 4if prevImageGCFailed {vLevel = 1prevImageGCFailed = false}glog.V(vLevel).Infof("Image garbage collection succeeded")}}, ImageGCPeriod, wait.NeverStop)
}

上面代码分别启动的容器的gc（containerGC.GarbageCollect()）和镜像的gc（imageManager.GarbageCollect()），
先看容器的gc pkg/kubelet/kuberuntime/kuberuntime_gc.go，

func (cgc *containerGC) GarbageCollect(gcPolicy kubecontainer.ContainerGCPolicy, allSourcesReady bool, evictNonDeletedPods bool) error {// Remove evictable containersif err := cgc.evictContainers(gcPolicy, allSourcesReady, evictNonDeletedPods); err != nil {return err}// Remove sandboxes with zero containersif err := cgc.evictSandboxes(evictNonDeletedPods); err != nil {return err}// Remove pod sandbox log directoryreturn cgc.evictPodLogsDirectories(allSourcesReady)
}

这里删除容器分为两个部分，一个是删除业务容器，一个是删除Sandbox容器，当然最后都会去删除他们的日志目录。

业务容器删除

先看删除业务容器的过程

func (cgc *containerGC) evictContainers(gcPolicy kubecontainer.ContainerGCPolicy, allSourcesReady bool, evictNonDeletedPods bool) error {// Separate containers by evict units.evictUnits, err := cgc.evictableContainers(gcPolicy.MinAge)if err != nil {return err}// Remove deleted pod containers if all sources are ready.if allSourcesReady {for key, unit := range evictUnits {if cgc.isPodDeleted(key.uid) || evictNonDeletedPods {cgc.removeOldestN(unit, len(unit)) // Remove all.delete(evictUnits, key)}}}// Enforce max containers per evict unit.if gcPolicy.MaxPerPodContainer >= 0 {cgc.enforceMaxContainersPerEvictUnit(evictUnits, gcPolicy.MaxPerPodContainer)}// Enforce max total number of containers.if gcPolicy.MaxContainers >= 0 && evictUnits.NumContainers() > gcPolicy.MaxContainers {// Leave an equal number of containers per evict unit (min: 1).numContainersPerEvictUnit := gcPolicy.MaxContainers / evictUnits.NumEvictUnits()if numContainersPerEvictUnit < 1 {numContainersPerEvictUnit = 1}cgc.enforceMaxContainersPerEvictUnit(evictUnits, numContainersPerEvictUnit)// If we still need to evict, evict oldest first.numContainers := evictUnits.NumContainers()if numContainers > gcPolicy.MaxContainers {flattened := make([]containerGCInfo, 0, numContainers)for key := range evictUnits {flattened = append(flattened, evictUnits[key]...)}sort.Sort(byCreated(flattened))cgc.removeOldestN(flattened, numContainers-gcPolicy.MaxContainers)}}return nil
}

上面的代码做的多层判断，首先是删除超过gcPolicy.MinAge时间死掉pod的容器，然后删除单个pod运行最大死亡容器gcPolicy.MaxPerPodContainer，最后是删除整个机器上面死亡容器的上限。
evictContainers是过去可以驱逐的容器（退出且超过gcPolicy.MinAge时间的容器）具体看下面：

func (cgc *containerGC) evictableContainers(minAge time.Duration) (containersByEvictUnit, error) {containers, err := cgc.manager.getKubeletContainers(true)...for _, container := range containers {if container.State == runtimeapi.ContainerState_CONTAINER_RUNNING {continue}createdAt := time.Unix(0, container.CreatedAt)if newestGCTime.Before(createdAt) {continue}...
}

然后是删除单个pod死亡容器上限的

func (cgc *containerGC) enforceMaxContainersPerEvictUnit(evictUnits containersByEvictUnit, MaxContainers int) {for key := range evictUnits {toRemove := len(evictUnits[key]) - MaxContainersif toRemove > 0 {evictUnits[key] = cgc.removeOldestN(evictUnits[key], toRemove)}}
}

最后是删除超过上限的死亡容器

numContainers := evictUnits.NumContainers()if numContainers > gcPolicy.MaxContainers {flattened := make([]containerGCInfo, 0, numContainers)for key := range evictUnits {flattened = append(flattened, evictUnits[key]...)}sort.Sort(byCreated(flattened))cgc.removeOldestN(flattened, numContainers-gcPolicy.MaxContainers)}

Sandbox容器删除

然后是删除Sandbox容器，这里pkg/kubelet/kuberuntime/kuberuntime_gc.go

func (cgc *containerGC) evictSandboxes(evictNonDeletedPods bool) error {containers, err := cgc.manager.getKubeletContainers(true)if err != nil {return err}sandboxes, err := cgc.manager.getKubeletSandboxes(true)if err != nil {return err}sandboxesByPod := make(sandboxesByPodUID)for _, sandbox := range sandboxes {podUID := types.UID(sandbox.Metadata.Uid)sandboxInfo := sandboxGCInfo{id:         sandbox.Id,createTime: time.Unix(0, sandbox.CreatedAt),}// Set ready sandboxes to be active.if sandbox.State == runtimeapi.PodSandboxState_SANDBOX_READY {sandboxInfo.active = true}// 查询这个Sandbox是否有关联容器hasContainers := falsesandboxID := sandbox.Idfor _, container := range containers {if container.PodSandboxId == sandboxID {hasContainers = truebreak}}if hasContainers {sandboxInfo.active = true}sandboxesByPod[podUID] = append(sandboxesByPod[podUID], sandboxInfo)}// Sort the sandboxes by age.for uid := range sandboxesByPod {sort.Sort(sandboxByCreated(sandboxesByPod[uid]))}for podUID, sandboxes := range sandboxesByPod {if cgc.isPodDeleted(podUID) || evictNonDeletedPods {// 如果这个pod是要被驱逐出这台机器的话，所以的Sandbox直接全部回收cgc.removeOldestNSandboxes(sandboxes, len(sandboxes))} else {// 如果不是则保留最新的一个cgc.removeOldestNSandboxes(sandboxes, len(sandboxes)-1)}}return nil
}