16 Handling Stateful Applications with StatefulSets
This chapter covers
- Managing stateful workloads via StatefulSet objects
- Exposing individual Pods via headless Services
- Understanding the difference between Deployments and StatefulSets
- Automating stateful workload management with Kubernetes Operators
Each of the three services in your Kiada suite is now deployed via a Deployment object. The Kiada and Quote services each have three replicas, while the Quiz service has only one because its data doesn’t allow it to scale easily. In this chapter, you’ll learn how to properly deploy and scale stateful workloads like the Quiz service with a StatefulSet.
Before you begin, create the kiada Namespace, change to the Chapter16/ directory and apply all manifests in the SETUP/ directory with the following command:
$ kubectl apply -n kiada -f SETUP -R
IMPORTANT
The examples in this chapter assume that the objects are created in the kiada Namespace. If you create them in a different location, you must update the DNS domain names in several places.
NOTE
You can find the code files for this chapter at https://github.com/luksa/kubernetes-in-action-2nd-edition/tree/master/Chapter16.
16.1 Introducing StatefulSets
Before you learn about StatefulSets and how they differ from Deployments, it’s good to know how the requirements of stateful workloads differ from those of their stateless counterparts.