Kubernetes ReplicaSets: 簡単な紹介

    apiVersion: apps/v1 # our API version
kind: ReplicaSet   # The kind we are creating
Metadata: # Specify all Metadata like name, labels
  name: some-name
  labels:
    app: some-App
    tier: some-Tier
Spec: 
  replicas: 3 # Here is where we tell k8s how many replicas we want
  Selector: # This is our label selector field. 
    matchLabels:
      tier: some-Tier
    matchExpressions:
      - {key: tier, operator: In, values: [some-Tier]} # we are using the set-based operators
  template:
    metadata:
      labels:
        app: some-App
        tier: someTier
    Spec: # This spec section should look like spec in a pod definition
      Containers:

    apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: myapp-replicas
  labels:
    app: myapp
    tier: frontend
spec:
  replicas: 3
  selector:
    matchLabels:
      tier: frontend
    matchExpressions:
      - {key: tier, operator: In, values: [frontend]}
  template:
    metadata:
      labels:
        app: myapp
        tier: frontend
    spec:
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80

    $ kubectl create -f replica.yaml
replicaset.apps "myapp-replicas" created

    $ kubectl get replicaset
NAME                            DESIRED   CURRENT   READY     AGE
myapp-replicas                  3         3         3         15s

    $ kubectl get pod
NAME                            READY     STATUS    RESTARTS   AGE
myapp-replicas-67rkp            1/1       Running   0          33s
myapp-replicas-6kfd8            1/1       Running   0          33s
myapp-replicas-s96sg            1/1       Running   0          33s

    $ kubectl describe replicaset myapp-replicas
Name:         myapp-replicas
Namespace:    default
Selector:     tier=frontend,tier in (frontend)
Labels:       app=myapp
              tier=frontend
Annotations:  
Replicas:     3 current / 3 desired
Pods Status:  3 Running / 0 Waiting / 0 Succeeded / 0 Failed
Pod Template:
  Labels:  app=myapp
           tier=frontend
  Containers:
   nginx:
    Image:        nginx
    Port:         80/TCP
    Host Port:    0/TCP
    Environment:  
    Mounts:       
  Volumes:        
Events:
  Type    Reason            Age   From                   Message
  ----    ------            ----  ----                   -------
  Normal  SuccessfulCreate  12m   replicaset-controller  Created pod: myapp-replicas-6kfd8
  Normal  SuccessfulCreate  12m   replicaset-controller  Created pod: myapp-replicas-67rkp
  Normal  SuccessfulCreate  12m   replicaset-controller  Created pod: myapp-replicas-s96sg