Hands-On Microservices with Kubernetes

Understanding a StatefulSet

At its core, a StatefulSet is a controller that manages a set of pods with some extra properties, such as ordering and uniqueness. The StatefulSet allows its set of pods to be deployed and scaled, while preserving their special properties. StatefulSets reached general availability (GA) status in Kubernetes 1.9. You can think of a StatefulSet as a souped-up deployment. Let's take a look at a sample StatefulSet for the user service, which uses a relational PostgresDB as its data store:

apiVersion: apps/v1kind: StatefulSetmetadata:  name: user-dbspec:  selector:    matchLabels:      svc: user      app: postgres  serviceName: user-db  replicas: 1  template:    metadata:      labels:        svc: user        app: postgres    spec: terminationGracePeriodSeconds: ...