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Sequential Breakdown of the Process

The sequence of events that transpired with the kubectl create -f replicaset.yaml command is as follows.

  • 1.Kubernetes client (kubectl) sent a request to the API server requesting the creation of a ReplicaSet defined in the replicaset.yaml file .
  • 2.The controller is watching the API server for new events, and it detected that there is a new ReplicaSet object.
  • 3.The controller creates 5 new pod definitions because we have configured replica value as 5 in file.
  • 4.Since the scheduler is watching the API server for new events, it detected that there are two unassigned Pods.
  • 5.The scheduler decided which node to assign the Pod and sent that information to the API server.
  • 6.Kubelet is also watching the API server. It detected that the two Pods were assigned to the node it is running on.
  • 7.Kubelet sent requests to Docker requesting the creation of the containers that form the Pod.
  • 8.Finally, Kubelet sent a request to the API server notifying it that the Pods

The sequence we described is useful when we want to understand everything that happened in the cluster from the moment we requested the creation of a new ReplicaSet. However, it might be too confusing so we’ll try to explain the same process through a diagram that more closely represents the cluster.