Core Kubernetes

12 etcd and the control plane

This chapter covers

• Comparing etcd v2 and v3
• Looking at a watch in Kubernetes
• Exploring the importance of strict consistency
• Load balancing against etcd nodes
• Looking at etcd’s security model in Kubernetes

As discussed in chapter 11, etcd is a key/value store with strong consistency guarantees. It’s similar to ZooKeeper, which is used for popular technologies like HBase and Kafka. A Kubernetes cluster at its core consists of

• The kubelet

• The scheduler

• The controller managers (KCM and CCM)

• The API server

These components all speak to one another by updating the API server. For example, if the scheduler wants to run a Pod on a specific node, it does so by modifying the Pod’s definition in the API server. ...