概述

Deployment是Kubernetes中最常用的Object，也是最典型的面试题，通过阅读源码，可以学习到标准的k8s-controller模式应该如何开发。

details

processNextWorkItem流程

• 拿到deploy对象: dc.dLister.Deployments(namespace).Get(name)
• 拿到replica对象: dc.getReplicaSetsForDeployment(ctx, d)
• 根据repicaset ID聚合pods: dc.getPodMapForDeployment(d, rsList)
• 逻辑分支
  • dp已被删除: dc.syncStatusOnly(ctx, d, rsList)
  • d.Spec.Paused: return dc.sync(ctx, d, rsList)
  • rollback: 已废弃annotation回滚功能
  • desired-replicas annotation(ScalingEvent): return dc.sync(ctx, d, rsList)
  • 根据d.Spec.Strategy.Type，这中间可能会创建新的replicaset: rolloutRecreate/rolloutRolling

dInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
    AddFunc:    dc.addDeployment,
    UpdateFunc: dc.updateDeployment,
    // This will enter the sync loop and no-op, because the deployment has been deleted from the store.
    DeleteFunc: dc.deleteDeployment,
})
rsInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
    AddFunc:    dc.addReplicaSet,
    UpdateFunc: dc.updateReplicaSet,
    DeleteFunc: dc.deleteReplicaSet,
})

func (dc *DeploymentController) processNextWorkItem(ctx context.Context) bool {
	key, quit := dc.queue.Get()
	if quit {
		return false
	}
	defer dc.queue.Done(key)

	err := dc.syncHandler(ctx, key.(string))
	dc.handleErr(err, key)

	return true
}

syncDeployment

• replicaset分为最新的和其他，最新的含义是和deploy tmpl字段一样中最新的
• 如果发现deploy没有对应的最新replicaset，会创建出新的replicaset
• 为什么deployment不直接管理Pod，而是要通过replicaset？
  • 我们通常只使用了deployment的基础功能，所以会觉得dp和rs很类似，但这是先入为主的概念
  • 实际上，rs所代表的副本集的功能确实是非常稳定的，但是k8s的开发者预见到了deployment的强大潜力，因此副本集的功能分离了出来
  • 事实上，deployment确实在应用中统治了一切无状态的workload，甚至能模拟出daemonset

func (dc *DeploymentController) syncDeployment(ctx context.Context, key string)

func (dc *DeploymentController) rolloutRolling(ctx context.Context, d *apps.Deployment, rsList []*apps.ReplicaSet) error

func (dc *DeploymentController) getAllReplicaSetsAndSyncRevision(ctx context.Context, d *apps.Deployment, rsList []*apps.ReplicaSet, createIfNotExisted bool) (*apps.ReplicaSet, []*apps.ReplicaSet, error)