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# 一、镜像更新策略简介
Deployment控制器支持两种镜像更新策略：重建更新和滚动更新（默认），可以通过strategy字段进行配置
配置资料如下：
```yaml
strategy:  # 指定新的Pod替换旧的Pod的策略，支持两个属性
  type:   # 指定策略类型，支持两种策略
    Recreate:    # 在创建出新的额Pod之前会先杀掉所有已存在的Pod
    RollingUpdate:    # 滚动更新，就是杀死一部分，就启动一部分，在更新的过程中，存在两个版本的Pod，可以做到业务无中断
  rollingUpdate:   # 当type为RollingUpdate时生效，用于为RollingUpdate设置参数，支持如下两个属性
    maxUnavailable:  # 用来指定在升级过程中不可用Pod的最大数量，默认为25%
    maxSurge:    # 用来指定在升级过程中可以超过期望的Pod的最大数量，默认为25%
```

# 二、重建更新
编辑 pc_deployment.yaml文件，内容如下，设置更新策略为重建
```yaml
apiVersion: v1
kind: Namespace
metadata:
  name: dev

---

apiVersion: apps/v1
kind: Deployment
metadata:
  name: pc-deployment
  namespace: dev
spec:
  replicas: 3
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: nginx-pod
  template:
    metadata:
      labels:
        app: nginx-pod
    spec:
      containers:
      - name: nginx
        image: nginx:1.17.1
```
然后使用如下命令创建资源
```bash
[root@master pod_controller]# kubectl apply -f pc_deployment.yaml
namespace/dev created
deployment.apps/pc-deployment created
[root@master pod_controller]#
```
此时可在另外一个终端中使用如下命令监控pod变化过程
```bash
kubectl get pod -n dev -w
```
然后更新镜像版本，可以通过修改yaml文件，然后使用如下命令修改
```bash
kubectl apply -f pc_deployment.yaml
```
也可以不修改yaml文件，通过如下命令直接修改镜像版本，如修改为1.17.3
```bash
kubectl set image deploy pc-depoyment nginx=nginx:1.17.3 -n dev
```
此时监控窗口输出如下，可以看出此时是一次性将三个pod杀掉，然后重新创建了三个pod
```bash
[root@master ~]# kubectl get pod -n dev -w
NAME                             READY   STATUS    RESTARTS   AGE
pc-deployment-5d9c9b97bb-cxsrn   1/1     Running   0          8s
pc-deployment-5d9c9b97bb-j5vfn   1/1     Running   0          8s
pc-deployment-5d9c9b97bb-z4hjg   1/1     Running   0          8s
pc-deployment-5d9c9b97bb-z4hjg   1/1     Terminating   0          30s
pc-deployment-5d9c9b97bb-j5vfn   1/1     Terminating   0          30s
pc-deployment-5d9c9b97bb-cxsrn   1/1     Terminating   0          30s
pc-deployment-5d9c9b97bb-z4hjg   0/1     Terminating   0          30s
pc-deployment-5d9c9b97bb-j5vfn   0/1     Terminating   0          30s
pc-deployment-5d9c9b97bb-cxsrn   0/1     Terminating   0          30s
pc-deployment-5d9c9b97bb-z4hjg   0/1     Terminating   0          34s
pc-deployment-5d9c9b97bb-z4hjg   0/1     Terminating   0          34s
pc-deployment-5d9c9b97bb-j5vfn   0/1     Terminating   0          34s
pc-deployment-5d9c9b97bb-j5vfn   0/1     Terminating   0          34s
pc-deployment-5d9c9b97bb-cxsrn   0/1     Terminating   0          40s
pc-deployment-5d9c9b97bb-cxsrn   0/1     Terminating   0          40s
pc-deployment-76fd8c7f84-jjtxb   0/1     Pending       0          0s
pc-deployment-76fd8c7f84-z9bwm   0/1     Pending       0          0s
pc-deployment-76fd8c7f84-jjtxb   0/1     Pending       0          0s
pc-deployment-76fd8c7f84-lwwjb   0/1     Pending       0          0s
pc-deployment-76fd8c7f84-z9bwm   0/1     Pending       0          0s
pc-deployment-76fd8c7f84-lwwjb   0/1     Pending       0          0s
pc-deployment-76fd8c7f84-jjtxb   0/1     ContainerCreating   0          0s
pc-deployment-76fd8c7f84-z9bwm   0/1     ContainerCreating   0          0s
pc-deployment-76fd8c7f84-lwwjb   0/1     ContainerCreating   0          0s
pc-deployment-76fd8c7f84-z9bwm   1/1     Running             0          1s
pc-deployment-76fd8c7f84-lwwjb   1/1     Running             0          1s
pc-deployment-76fd8c7f84-jjtxb   1/1     Running             0          1s
```
# 三、滚动更新
编写pc_deployment.yaml文件，内容如下，为了演示滚动效果，这里设置3个副本，初始化镜像设置为1.17.1的版本，滚动更新比例设置为25%，如下：
```yaml
apiVersion: v1
kind: Namespace
metadata:
  name: dev

---

apiVersion: apps/v1
kind: Deployment
metadata:
  name: pc-deployment
  namespace: dev
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 25%
      maxSurge: 25%
  selector:
    matchLabels:
      app: nginx-pod
  template:
    metadata:
      labels:
        app: nginx-pod
    spec:
      containers:
      - name: nginx
        image: nginx:1.17.1
```
然后使用如下命令创建资源
```bash
[root@master pod_controller]# kubectl apply -f pc_deployment.yaml
namespace/dev created
deployment.apps/pc-deployment created
[root@master pod_controller]#
```
这里同样打开一个窗口使用如下命令监视pod的状态
```bash
kubectl get pod -n dev -w
```
这里同样也可以通过修改yaml文件中镜像的版本号和使用kubectl apply -f pc_deployment.yaml命令的方式，或者可以直接通过使用如下命令设置镜像版本号
```bash
[root@master pod_controller]# kubectl set image deploy pc-deployment nginx=nginx:1.17.3 -n dev
deployment.apps/pc-deployment image updated
[root@master pod_controller]#
```
此时通过监视窗口可以看到pod的变化过程，即先创建一个pod，然后停一个pod，再创建一个pod，在停一个pod，再创建一个pod，再停一个pod
```bash
[root@master ~]# kubectl get pod -n dev -w
NAME                             READY   STATUS    RESTARTS   AGE
pc-deployment-5d9c9b97bb-pqm9j   1/1     Running   0          59s
pc-deployment-5d9c9b97bb-ql5ps   1/1     Running   0          60s
pc-deployment-5d9c9b97bb-w49wz   1/1     Running   0          61s
pc-deployment-76fd8c7f84-w4pw7   0/1     Pending   0          0s
pc-deployment-76fd8c7f84-w4pw7   0/1     Pending   0          0s
pc-deployment-76fd8c7f84-w4pw7   0/1     ContainerCreating   0          0s
pc-deployment-76fd8c7f84-w4pw7   1/1     Running             0          1s
pc-deployment-5d9c9b97bb-pqm9j   1/1     Terminating         0          67s
pc-deployment-76fd8c7f84-kmrb7   0/1     Pending             0          0s
pc-deployment-76fd8c7f84-kmrb7   0/1     Pending             0          0s
pc-deployment-76fd8c7f84-kmrb7   0/1     ContainerCreating   0          0s
pc-deployment-5d9c9b97bb-pqm9j   0/1     Terminating         0          67s
pc-deployment-5d9c9b97bb-pqm9j   0/1     Terminating         0          68s
pc-deployment-5d9c9b97bb-pqm9j   0/1     Terminating         0          68s
pc-deployment-76fd8c7f84-kmrb7   1/1     Running             0          1s
pc-deployment-5d9c9b97bb-ql5ps   1/1     Terminating         0          69s
pc-deployment-76fd8c7f84-h4d87   0/1     Pending             0          0s
pc-deployment-76fd8c7f84-h4d87   0/1     Pending             0          0s
pc-deployment-76fd8c7f84-h4d87   0/1     ContainerCreating   0          0s
pc-deployment-5d9c9b97bb-ql5ps   0/1     Terminating         0          70s
pc-deployment-76fd8c7f84-h4d87   1/1     Running             0          1s
pc-deployment-5d9c9b97bb-w49wz   1/1     Terminating         0          71s
pc-deployment-5d9c9b97bb-ql5ps   0/1     Terminating         0          71s
pc-deployment-5d9c9b97bb-ql5ps   0/1     Terminating         0          71s
pc-deployment-5d9c9b97bb-w49wz   0/1     Terminating         0          72s
pc-deployment-5d9c9b97bb-w49wz   0/1     Terminating         0          84s
pc-deployment-5d9c9b97bb-w49wz   0/1     Terminating         0          84s

```
滚动更新过程如下图所示
![](/static/upload/20220523_135021.png)

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