Just finished reading Nigel Poulton's The Kubernetes Book. I'm left with the question of whether or not a Deployment can specify multiple ReplicaSets.
When I think Deployment, I think of it in the traditional sense of an entire application being deployed. Or is there meant to be a Deployment for each microservice?
apiVersion: apps/v1beta2
kind: Deployment
metadata:
name: hello-deploy
spec:
replicas: 10
selector:
matchLabels:
app: hello-world
minReadySeconds: 10
strategy:
type: RollingUpdate
rollingUpdate:
maxUnavailable: 1
maxSurge: 1
template:
metadata:
labels:
app: hello-world
spec:
containers:
- name: hello-pod
image: nigelpoulton/k8sbook : latest
ports:
- containerPort: 8080It is meant to be a deployment of each microservice.
You can also manage the quantity of "deployed services" of each microservices type. So for instance, if you want to deploy Service A (Docker image with an Java service) 5 times, you have a deployment resulting 5 pods. Each pod contains the image of Service A.
If you deploy a new version of this Service A (Docker image with an Java service), Kubernetes is able to do a rolling update and manage the shut down of the old Java service type (the existing pods) and creates 5 new pods with the new Java Service A.2 (a new docker image).
Thus your whole microservices application/infrastructure is build upon multiple deployments. Each generating Kubernetes pods, which are published by Kubernetes services.
A deployment contains a single pod template, and generates one replicaset per revision