apiVersion: apps/v1kind: Deploymentmetadata:  creationTimestamp: null  labels:    app: sample  name: samplespec:  replicas: 1  selector:    matchLabels:      app: sample  strategy: {}  template:    metadata:      creationTimestamp: null      labels:        app: sample    spec:      containers:      - image: addozhang/k8s-container-sequence-sidecar:latest        name: sidecar        imagePullPolicy: IfNotPresent        lifecycle:          postStart:            exec:              command:                - /entrypoint                - wait      - image: busybox:latest        name: app        imagePullPolicy: IfNotPresent        command: ["/bin/sh","-c"]        args: ["date; echo 'app container started'; tail -f /dev/null"]

// SyncPod syncs the running pod into the desired pod by executing following steps:////  1. Compute sandbox and container changes.//  2. Kill pod sandbox if necessary.//  3. Kill any containers that should not be running.//  4. Create sandbox if necessary.//  5. Create ephemeral containers.//  6. Create init containers.//  7. Create normal containers.func (m *kubeGenericRuntimeManager) SyncPod(pod *v1.Pod, podStatus *kubecontainer.PodStatus, pullSecrets []v1.Secret, backOff *flowcontrol.Backoff) (result kubecontainer.PodSyncResult) {    ...    // Step 7: start containers in podContainerChanges.ContainersToStart.    for _, idx := range podContainerChanges.ContainersToStart {        start("container", containerStartSpec(&pod.Spec.Containers[idx]))    }    return}

// startContainer starts a container and returns a message indicates why it is failed on error.// It starts the container through the following steps:// * pull the image// * create the container// * start the container// * run the post start lifecycle hooks (if applicable)func (m *kubeGenericRuntimeManager) startContainer(podSandboxID string, podSandboxConfig *runtimeapi.PodSandboxConfig, spec *startSpec, pod *v1.Pod, podStatus *kubecontainer.PodStatus, pullSecrets []v1.Secret, podIP string, podIPs []string) (string, error) {     ...    // Step 4: execute the post start hook.    if container.Lifecycle != nil && container.Lifecycle.PostStart != nil {        kubeContainerID := kubecontainer.ContainerID{            Type: m.runtimeName,            ID:   containerID,        }        msg, handlerErr := m.runner.Run(kubeContainerID, pod, container, container.Lifecycle.PostStart)        if handlerErr != nil {            m.recordContainerEvent(pod, container, kubeContainerID.ID, v1.EventTypeWarning, events.FailedPostStartHook, msg)            if err := m.killContainer(pod, kubeContainerID, container.Name, "FailedPostStartHook", reasonFailedPostStartHook, nil); err != nil {                klog.ErrorS(fmt.Errorf("%s: %v", ErrPostStartHook, handlerErr), "Failed to kill container", "pod", klog.KObj(pod),                    "podUID", pod.UID, "containerName", container.Name, "containerID", kubeContainerID.String())            }            return msg, fmt.Errorf("%s: %v", ErrPostStartHook, handlerErr)        }    }    return "", nil}

for time.Now().Before(timeoutAt) {    err = checkIfReady(client, url)    if err == nil {        log.Println("sidecar is ready")        return nil    }    log.Println("sidecar is not ready")    time.Sleep(time.Duration(periodMillis) * time.Millisecond)}return fmt.Errorf("sidecar is not ready in %d second(s)", timeoutSeconds)