Sequential Breakdown and Verification of the Update Process

Sequential breakdown of the update process

Let’s understand what happens when we execute the kops update command.

1. kOps retrieves the desired state from the S3 bucket.

2. kOps sends requests to AWS API to change the values of the workers ASG.

3. AWS modifies the values of the workers ASG by increasing them by 1.

4. ASG created a new EC2 instance to comply with the new sizing.

5. Protokube installs Kubelet and Docker and creates the manifest file with the list of Pods.

6. Kubelet reads the manifest file and runs the container that forms the kube-proxy Pod (the only Pod on the worker nodes).

7. Kubelet sends a request to the kube-apiserver (through the dns-controller) to register the new node and join it to the cluster. The information about the new node is stored in etcd.

This process is almost identical to the one used to create the nodes of the cluster.