K8S ReplicaSet & ReplicationController

RC是RS的老版本API，代碼都是一份。

For RC, the objects are converted on the way in and out (see ../replication/), as if ReplicationController were just an older API version of ReplicaSet. However, RC and RS still have separate storage and separate instantiations of the ReplicaSetController object.

type ReplicationManager struct {
    replicaset.ReplicaSetController
}

code

K8S controller基本都是一個套路，通過Informer注冊事件處理函數(shù)，Add事件處理都是將ev入隊；
controller的run方法會啟動一個goroutine，每隔一秒消費queue。所以跳過上述步驟，直接進入同步邏輯。

func (rsc *ReplicaSetController) syncReplicaSet(key string) error {
    namespace, name, err := cache.SplitMetaNamespaceKey(key)
    rs, err := rsc.rsLister.ReplicaSets(namespace).Get(name)
    
    // 貌似每個controller都會很暴力的獲取全量Pods，這個有點狠，為什么不加點過濾條件呢？
    // 內(nèi)存選出rs selector的Pods
    allPods, err := rsc.podLister.Pods(rs.Namespace).List(labels.Everything())
    for _, pod := range allPods {
        if controller.IsPodActive(pod) {
            filteredPods = append(filteredPods, pod)
        }
    }
    filteredPods, err = rsc.claimPods(rs, selector, filteredPods)
    
    // 老套路，管理Pods，使之達到預(yù)期
    rsc.manageReplicas(filteredPods, rs)
}

func (rsc *ReplicaSetController) manageReplicas(filteredPods []*v1.Pod, rs *apps.ReplicaSet) error {
    diff := len(filteredPods) - int(*(rs.Spec.Replicas))
    rsKey, err := controller.KeyFunc(rs)
    
    if diff < 0 {
        // "Too few replicas for %v %s/%s, need %d, creating %d", rsc.Kind, rs.Namespace, rs.Name, *(rs.Spec.Replicas), diff
        // batch create, 所有controller都這樣，類似TCP擁塞控制，并發(fā)創(chuàng)建1,2,4。。。
        successfulCreations, err := slowStartBatch(diff, controller.SlowStartInitialBatchSize, func() error {
            boolPtr := func(b bool) *bool { return &b }
            controllerRef := &metav1.OwnerReference{
                APIVersion:         rsc.GroupVersion().String(),
                Kind:               rsc.Kind,
                Name:               rs.Name,
                UID:                rs.UID,
                BlockOwnerDeletion: boolPtr(true),
                Controller:         boolPtr(true),
            }
            err := rsc.podControl.CreatePodsWithControllerRef(rs.Namespace, &rs.Spec.Template, rs, controllerRef)
        })        
    } else if diff > 0 {
        // "Too many replicas for %v %s/%s, need %d, deleting %d", rsc.Kind, rs.Namespace, rs.Name, *(rs.Spec.Replicas), diff
        
        // Choose which Pods to delete, preferring those in earlier phases of startup.
        podsToDelete := getPodsToDelete(filteredPods, diff)
        
        for _, pod := range podsToDelete {
            go func(targetPod *v1.Pod) {
                err := rsc.podControl.DeletePod(rs.Namespace, targetPod.Name, rs); 
            }(pod)
        }
    }
}