// updatePodWithRetries retries updating the given pod on conflict with the following steps:
// 1. Get latest resource
// 2. applyUpdate
// 3. Update the resource
func updatePodWithRetries(c client.Interface, namespace string, pod *api.Pod, applyUpdate updatePodFunc) (*api.Pod, error) {
	// Deep copy the pod in case we failed on Get during retry loop
	obj, err := api.Scheme.Copy(pod)
	if err != nil {
		return nil, fmt.Errorf("failed to deep copy pod before updating it: %v", err)
	}
	oldPod := obj.(*api.Pod)
	err = client.RetryOnConflict(client.DefaultBackoff, func() (e error) {
		// Apply the update, then attempt to push it to the apiserver.
		applyUpdate(pod)
		if pod, e = c.Pods(namespace).Update(pod); e == nil {
			return
		}
		updateErr := e
		if pod, e = c.Pods(namespace).Get(oldPod.Name); e != nil {
			pod = oldPod
		}
		// Only return the error from update
		return updateErr
	})
	// If the error is non-nil the returned pod cannot be trusted, if it is nil, the returned
	// controller contains the applied update.
	return pod, err
}
func AddDeploymentKeyToReplicationController(oldRc *api.ReplicationController, client client.Interface, deploymentKey, deploymentValue, namespace string, out io.Writer) (*api.ReplicationController, error) {
	var err error
	// First, update the template label.  This ensures that any newly created pods will have the new label
	applyUpdate := func(rc *api.ReplicationController) {
		if rc.Spec.Template.Labels == nil {
			rc.Spec.Template.Labels = map[string]string{}
		}
		rc.Spec.Template.Labels[deploymentKey] = deploymentValue
	}
	if oldRc, err = updateRcWithRetries(client, namespace, oldRc, applyUpdate); err != nil {
		return nil, err
	}

	// Update all pods managed by the rc to have the new hash label, so they are correctly adopted
	// TODO: extract the code from the label command and re-use it here.
	selector := labels.SelectorFromSet(oldRc.Spec.Selector)
	options := api.ListOptions{LabelSelector: selector}
	podList, err := client.Pods(namespace).List(options)
	if err != nil {
		return nil, err
	}
	for ix := range podList.Items {
		pod := &podList.Items[ix]
		applyUpdate := func(p *api.Pod) {
			if p.Labels == nil {
				p.Labels = map[string]string{
					deploymentKey: deploymentValue,
				}
			} else {
				p.Labels[deploymentKey] = deploymentValue
			}
		}
		if pod, err = updatePodWithRetries(client, namespace, pod, applyUpdate); err != nil {
			return nil, err
		}
	}

	if oldRc.Spec.Selector == nil {
		oldRc.Spec.Selector = map[string]string{}
	}
	// Copy the old selector, so that we can scrub out any orphaned pods
	selectorCopy := map[string]string{}
	for k, v := range oldRc.Spec.Selector {
		selectorCopy[k] = v
	}
	applyUpdate = func(rc *api.ReplicationController) {
		rc.Spec.Selector[deploymentKey] = deploymentValue
	}
	// Update the selector of the rc so it manages all the pods we updated above
	if oldRc, err = updateRcWithRetries(client, namespace, oldRc, applyUpdate); err != nil {
		return nil, err
	}

	// Clean up any orphaned pods that don't have the new label, this can happen if the rc manager
	// doesn't see the update to its pod template and creates a new pod with the old labels after
	// we've finished re-adopting existing pods to the rc.
	selector = labels.SelectorFromSet(selectorCopy)
	options = api.ListOptions{LabelSelector: selector}
	podList, err = client.Pods(namespace).List(options)
	for ix := range podList.Items {
		pod := &podList.Items[ix]
		if value, found := pod.Labels[deploymentKey]; !found || value != deploymentValue {
			if err := client.Pods(namespace).Delete(pod.Name, nil); err != nil {
				return nil, err
			}
		}
	}

	return oldRc, nil
}