如何实现Pod的创建和管理

// computePodActions checks whether the pod spec has changed and returns the changes if true.

func (m *kubeGenericRuntimeManager) computePodActions(pod *v1.Pod, podStatus *kubecontainer.PodStatus) podActions {

// 1. 对比sandbox状态，计算是否需要创建sandbox，以及当前sandbox id

createPodSandbox, attempt, sandboxID := m.podSandboxChanged(pod, podStatus)

changes := podActions{

KillPod: createPodSandbox,

CreateSandbox: createPodSandbox,

SandboxID: sandboxID,

Attempt: attempt,

ContainersToStart: []int{},

ContainersToKill: make(map[kubecontainer.ContainerID]containerToKillInfo),

}

// 2. 需要新建sandbox，一旦进入该分支就必定return，之后代码不再执行

if createPodSandbox {

....

// 在新建sandbox分支中，若存在init容器，则取第一个，返回

if len(pod.Spec.InitContainers) != 0 {

// Pod has init containers, return the first one.

changes.NextInitContainerToStart = &pod.Spec.InitContainers[0]

return changes

}

// 不存在init容器，直接跑工作containers

for idx, c := range pod.Spec.Containers {

if containerSucceeded(&c, podStatus) && pod.Spec.RestartPolicy == v1.RestartPolicyOnFailure {

continue

}

changes.ContainersToStart = append(changes.ContainersToStart, idx)

}

return changes

}

// 3. sandbox已运行，启动init容器。寻找下一个需要执行的init容器

initLastStatus, next, done := findNextInitContainerToRun(pod, podStatus)

if !done {

if next != nil {

initFailed := initLastStatus != nil && isContainerFailed(initLastStatus)

if initFailed && !shouldRestartOnFailure(pod) {

changes.KillPod = true

} else {

changes.NextInitContainerToStart = next

}

}

// 若init未完成，直接返回

return changes

}

// 4. init已完成，计算需要kill&start的工作container

keepCount := 0

for idx, container := range pod.Spec.Containers {

.....

}

// 5. 是否需要kill pod

if keepCount == 0 && len(changes.ContainersToStart) == 0 {

changes.KillPod = true

}

return changes

}

func (m *kubeGenericRuntimeManager) SyncPod(pod *v1.Pod, _ v1.PodStatus, podStatus *kubecontainer.PodStatus, pullSecrets []v1.Secret, backOff *flowcontrol.Backoff) (result kubecontainer.PodSyncResult) {

// 1. 计算pod actions，见上文

podContainerChanges := m.computePodActions(pod, podStatus)

.....

// 2. 需要情况下执行kill pod

if podContainerChanges.KillPod {

....

killResult := m.killPodWithSyncResult(pod, kubecontainer.ConvertPodStatusToRunningPod(m.runtimeName, podStatus), nil)

....

} else {

// 3. 不需要kill pod，但需要kill工作container

for containerID, containerInfo := range podContainerChanges.ContainersToKill {

....

if err := m.killContainer(pod, containerID, containerInfo.name, containerInfo.message, nil); err != nil {

...

return

}

}

}

.....

// 4. 按需创建sandbox

podSandboxID := podContainerChanges.SandboxID

if podContainerChanges.CreateSandbox {

.....

podSandboxID, msg, err = m.createPodSandbox(pod, podContainerChanges.Attempt)

....

}

....

// 5. 运行next init container

if container := podContainerChanges.NextInitContainerToStart; container != nil {

....

if msg, err := m.startContainer(podSandboxID, podSandboxConfig, container, pod, podStatus, pullSecrets, podIP); err != nil {

startContainerResult.Fail(err, msg)

utilruntime.HandleError(fmt.Errorf("init container start failed: %v: %s", err, msg))

return

}

....

}

// 6. 运行工作containers。注意，根据computePodActions，若NextInitContainerToStart不为空，则不存在ContainersToStart ，即这个循环在当前这个SyncPod中不会被执行

for _, idx := range podContainerChanges.ContainersToStart {

....

if msg, err := m.startContainer(podSandboxID, podSandboxConfig, container, pod, podStatus, pullSecrets, podIP); err != nil {

startContainerResult.Fail(err, msg)

// known errors that are logged in other places are logged at higher levels here to avoid

// repetitive log spam

switch {

case err == images.ErrImagePullBackOff:

glog.V(3).Infof("container start failed: %v: %s", err, msg)

default:

utilruntime.HandleError(fmt.Errorf("container start failed: %v: %s", err, msg))

}

continue

}

}

return

}