觀察現況
我們透過 ReplicaSet 物件提交到 K8s API 的方式建立副本管理。
先行察看兩個物件，可以得知哪一個 pod 尚未套用 ReplicaSet 物件～
kubectl get pods
kubectl get rs
[user@minikube ~]$ kubectl get pods
NAME READY STATUS RESTARTS AGE
hello-kitty 1/1 Running 0 6d
hello-minikube-7c77b68cff-ncqmn 1/1 Running 1 11d
hello-moto-6456dff9f-67jh5 1/1 Running 0 5d
[user@minikube ~]$ kubectl get rs
NAME DESIRED CURRENT READY AGE
hello-minikube-7c77b68cff 1 1 1 11d
hello-moto-6456dff9f 1 1 1 5d
另一個方式查看該 pod 是否已有 ReplicaSet 管理
kubectl get pods -o yaml
如果顯示的內容中，有出現kind: ReplicaSet物件，即代表受管理中
...
ownerReferences:
- apiVersion: extensions/v1beta1
blockOwnerDeletion: true
controller: true
kind: ReplicaSet
name: hello-moto-6456dff9f
新增 ReplicaSet 實例
經比對，pod hello-kitty 尚未套用 ReplicaSet，可以最為下列範例～
新增 hello-kitty 的 ReplicaSet 物件～rs-hello-kitty.yaml
apiVersion: extensions/v1beta1
kind: ReplicaSet
metadata:
name: hello-kitty
spec:
replicas: 2
template:
metadata:
labels:
run: hello-kitty
spec:
containers:
- name: hello-kitty
image: "k8s.gcr.io/echoserver:1.10"
套用 ReplicaSet 物件之前 Pod 狀態：
[user@minikube ~]$ kubectl get pods hello-kitty -o wide
NAME READY STATUS RESTARTS AGE IP NODE
hello-kitty 1/1 Running 0 5d 172.17.0.6 minikube
套用 ReplicaSet 物件：
[user@minikube ~]$ kubectl apply -f kk8s/rs-hello-kitty.yaml
replicaset.extensions/hello-kitty created
套用 ReplicaSet 物件之後 Pod 狀態：
[user@minikube ~]$ kubectl get pods
NAME READY STATUS RESTARTS AGE
hello-kitty 1/1 Running 0 6d
hello-kitty-lk7lg 1/1 Running 0 1m
hello-kitty-x94s2 1/1 Running 0 1m
hello-minikube-7c77b68cff-ncqmn 1/1 Running 1 11d
hello-moto-6456dff9f-67jh5 1/1 Running 0 5d
檢查 ReplicaSet，可以看見裏頭的 Labels、replicas 資訊：
[user@minikube ~]$ kubectl describe rs hello-kitty
Name: hello-kitty
Namespace: default
Selector: run=hello-kitty
Labels: run=hello-kitty
Annotations: kubectl.kubernetes.io/last-applied-configuration:
{"apiVersion":"extensions/v1beta1","kind":"ReplicaSet","metadata":{"annotations":{},"name":"hello-kitty","namespace":"default"},"spec":{"r...
Replicas: 2 current / 2 desired
Pods Status: 2 Running / 0 Waiting / 0 Succeeded / 0 Failed
Pod Template:
Labels: run=hello-kitty
Containers:
hello-kitty:
Image: k8s.gcr.io/echoserver:1.10
Port: <none>
Host Port: <none>
Environment: <none>
Mounts: <none>
Volumes: <none>
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal SuccessfulCreate 84s replicaset-controller Created pod: hello-kitty-lk7lg
Normal SuccessfulCreate 84s replicaset-controller Created pod: hello-kitty-x94s2
Scale Pod 方式一
進行擴展 Pod[2 --> 4]，透過指令kubectl scale
[user@minikube ~]$ kubectl scale --replicas=4 rs/hello-kitty
replicaset.extensions/hello-kitty scaled
[user@minikube ~]$ kubectl get rs hello-kitty
NAME DESIRED CURRENT READY AGE
hello-kitty 4 4 4 9h
[user@minikube ~]$ kubectl get pods
NAME READY STATUS RESTARTS AGE
hello-kitty 1/1 Running 0 6d
hello-kitty-d7tfq 1/1 Running 0 22s
hello-kitty-lk7lg 1/1 Running 0 9h
hello-kitty-x94s2 1/1 Running 0 9h
hello-kitty-zgrb8 1/1 Running 0 22s
hello-minikube-7c77b68cff-ncqmn 1/1 Running 1 11d
hello-moto-6456dff9f-67jh5 1/1 Running 0 6d
Scale Pod 方式二
透過 kubectl apply 進行宣告式scale[4 --> 3]
編輯 rs-hello-kitty.yaml 內容中的 replicas: value 進行管理
apiVersion: extensions/v1beta1
kind: ReplicaSet
metadata:
name: hello-kitty
spec:
replicas: 3 # 修改此行 value
# 套用新 replicas value 設定
[user@minikube ~]$ kubectl apply -f kk8s/rs-hello-kitty.yaml
replicaset.extensions/hello-kitty configured
# 確認已經生效，從剛剛稍早 pod hello-kitty 4個，變成 3個。
[user@minikube ~]$ kubectl get rs hello-kitty
NAME DESIRED CURRENT READY AGE
hello-kitty 3 3 3 10h
# 觀察 pod 變化，副本 hello-kitty-d7tfq 正在消失中，狀態：Terminating
[user@minikube ~]$ kubectl get pods
NAME READY STATUS RESTARTS AGE
hello-kitty 1/1 Running 0 6d
hello-kitty-d7tfq 1/1 Terminating 0 15m
hello-kitty-lk7lg 1/1 Running 0 10h
hello-kitty-x94s2 1/1 Running 0 10h
hello-kitty-zgrb8 1/1 Running 0 15m
hello-minikube-7c77b68cff-ncqmn 1/1 Running 1 11d
hello-moto-6456dff9f-67jh5 1/1 Running 0 6d
# 觀察 pod 變化，確認副本 pod hello-kitty-XXXXX 剩下3個。
[user@minikube ~]$ kubectl get pods
NAME READY STATUS RESTARTS AGE
hello-kitty 1/1 Running 0 6d
hello-kitty-lk7lg 1/1 Running 0 10h
hello-kitty-x94s2 1/1 Running 0 10h
hello-kitty-zgrb8 1/1 Running 0 16m
hello-minikube-7c77b68cff-ncqmn 1/1 Running 1 11d
hello-moto-6456dff9f-67jh5 1/1 Running 0 6d
Scale Pod 方法差異
上述用了兩種方式進行 pod scale，kubectl scale --replicas跟kubectl apply -f
scale pod 目的與效果是相同的，但其實意義上，是有所不同的～
kubectl scale --replicas指令，適合自己工作上運用，但自己也要清楚當前 replicas valus。
kubectl apply -f是透過宣告式 yaml 檔案進行 replicas valus 管理，非常適合納入版控系統並搭配自動化腳本進行管理。進而更加適合團隊性質的協同合作需求。
你會希望我做過什麼變動，我也必須讓大家知道做過哪些變動，這是 DevOps 精神。
