k8s入门-Deployment控制器

た入场券 2023-02-12 14:28 41阅读 0赞

Deployment 为 Pod 和 ReplicaSet（下一代 Replication Controller）提供声明式更新，有了Deployment之后我们就不再单独的使用RC和RS了。 您只需要在 Deployment 中描述您想要的目标状态是什么，Deployment controller 就会帮您将 Pod 和 ReplicaSet 的实际状态改变到您的目标状态。 Deployment集成了上线部署、滚动升级、创建副本、暂停上线任务，恢复上线任务，回滚到以前某一版本（成功/稳定）的Deployment等功能，在某种程度上，Deployment可以帮我们实现无人值守的上线，大大降低我们的上线过程的复杂沟通、操作风险。

## 一、创建Deployment ##

Deployment对象的创建同样是一开YAML的配置文件。

[root@k8s-01 ~]# cat nginx-deployment.yaml 
    apiVersion: apps/v1
    kind: Deployment
    metadata:
      name: nginx-deployment
      labels:
        app: nginx
    spec:
      replicas: 3
      selector:
        matchLabels:
          app: nginx
      template:
        metadata:
          labels:
            app: nginx
        spec:
          containers:
          - name: nginx
            image: nginx:1.13.12
            ports:
            - containerPort: 80

可以发现，这里我特意在镜像中指定了一下nginx的版本，以方便后面升级的时候做对比。

使用kubectl创建Deployment

[root@k8s-01 ~]# kubectl create -f nginx-deployment.yaml
    deployment.apps/nginx-deployment created

查看Deployment

[root@k8s-01 ~]# kubectl get deployment
    NAME               READY   UP-TO-DATE   AVAILABLE   AGE
    nginx-deployment   3/3     3            3           16s

*  UP-TO-DATE 的 replica 的数目已经达到了配置中要求的数目。
 *  CURRENT 的 replica 数表示 Deployment 管理的 replica 数量
 *  AVAILABLE 的 replica 数是当前可用的 replica 数量。

查看RS和pod

[root@k8s-01 ~]# kubectl get rs
    NAME                          DESIRED   CURRENT   READY   AGE
    nginx-deployment-56689dc4b8   3         3         3       29s
    
    [root@k8s-01 ~]# kubectl get pod
    NAME                                READY   STATUS             RESTARTS   AGE
    nginx-deployment-56689dc4b8-9v72r   1/1     Running            1          26m
    nginx-deployment-56689dc4b8-mt4n2   1/1     Running            1          26m
    nginx-deployment-56689dc4b8-twlx2   1/1     Running            1          26m

查看Deployment扩展信息

[root@k8s-01 ~]# kubectl get deployment -o wide
    NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES          SELECTOR
    nginx-deployment   3/3     3            3           28m   nginx        nginx:1.13.12   app=nginx

查看pod的lables

[root@k8s-01 ~]# kubectl get pods --show-labels
    NAME                                READY   STATUS             RESTARTS   AGE   LABELS
    nginx-deployment-56689dc4b8-9v72r   1/1     Running            1          30m   app=nginx,pod-template-hash=56689dc4b8
    nginx-deployment-56689dc4b8-mt4n2   1/1     Running            1          30m   app=nginx,pod-template-hash=56689dc4b8
    nginx-deployment-56689dc4b8-twlx2   1/1     Running            1          30m   app=nginx,pod-template-hash=56689dc4b8

注意： `pod-template-has`这个 label 不是用户指定的！

注意上面示例输出中的 pod label 里的 pod-template-hash label。当 Deployment 创建或者接管 ReplicaSet 时，Deployment controller 会自动为 Pod 添加 pod-template-hash label。这样做的目的是防止 Deployment 的子ReplicaSet 的 pod 名字重复。通过将 ReplicaSet 的 PodTemplate 进行哈希散列，使用生成的哈希值作为 label 的值，并添加到 ReplicaSet selector 里、 pod template label 和 ReplicaSet 管理中的 Pod 上。

## 二、更新Deployment ##

更新Deployment，并增加–recode参数

[root@k8s-01 ~]# kubectl set image deployment nginx-deployment nginx=nginx:1.14.2 --record
    deployment.apps/nginx-deployment image updated

查看更新状态

[root@k8s-01 ~]# kubectl rollout status deployment nginx-deployment
    deployment "nginx-deployment" successfully rolled out

查看更新后的Deploymnet

[root@k8s-01 ~]# kubectl get deployment -o wide
    NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES         SELECTOR
    nginx-deployment   3/3     3            3           49m   nginx        nginx:1.14.2   app=nginx

可以看到，一开始定义的nginx版本是1.13.12，现在已经变成了1.14.2 。

## 三、Deployment升级历史 ##

查看升级历史

[root@k8s-01 ~]# kubectl rollout history deployment nginx-deployment
    deployment.apps/nginx-deployment 
    REVISION  CHANGE-CAUSE
    1         <none>
    2         kubectl set image deployment nginx-deployment nginx=nginx:1.14.2 --record=true

因为我们创建 Deployment 的时候使用了–record参数可以记录命令，我们可以很方便的查看每次 revision 的变化。可以看到有两次的历史记录。

查看单个revision 的详细信息：

[root@k8s-01 ~]# kubectl rollout history deployment nginx-deployment --revision=1 
    deployment.apps/nginx-deployment with revision #1
    Pod Template:
      Labels:       app=nginx
            pod-template-hash=56689dc4b8
      Containers:
       nginx:
        Image:      nginx:1.13.12
        Port:       80/TCP
        Host Port:  0/TCP
        Environment:        <none>
        Mounts:     <none>
      Volumes:      <none>

## 四、Deployment版本回滚 ##

回滚到上一个版本

[root@k8s-01 ~]# kubectl rollout undo deployment nginx-deployment
    deployment.apps/nginx-deployment rolled back
    
    [root@k8s-01 ~]# kubectl get deployment -o wide
    NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES          SELECTOR
    nginx-deployment   3/3     3            3           54m   nginx        nginx:1.13.12   app=nginx

很神奇吧，可以直接进行回滚，真是太舒服了。

还可以使用`--revision`参数指定某个历史版本：

[root@k8s-01 ~]# kubectl rollout undo deployment nginx-deployment --to-revision=2 
    deployment.apps/nginx-deployment rolled back
    
    [root@k8s-01 ~]# kubectl get deployment -o wide 
    NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES         SELECTOR
    nginx-deployment   3/3     3            3           57m   nginx        nginx:1.14.2   app=nginx

注意：版本号在Deployment的升级历史中查找

## 五、Deployment扩容 ##

[root@k8s-01 ~]# kubectl scale deployment nginx-deployment --replicas 2
    deployment.apps/nginx-deployment scaled
    
    [root@k8s-01 ~]# kubectl get pod
    NAME                                READY   STATUS             RESTARTS   AGE
    nginx-deployment-574b87c764-b6jhm   1/1     Running            0          3m25s
    nginx-deployment-574b87c764-tgsb8   1/1     Running            0          3m24s
    
    [root@k8s-01 ~]# kubectl get deployment
    NAME               READY   UP-TO-DATE   AVAILABLE   AGE
    nginx-deployment   2/2     2            2           63m
    
    
    [root@k8s-01 ~]# kubectl scale deployment nginx-deployment --replicas 4
    deployment.apps/nginx-deployment scaled
    
    [root@k8s-01 ~]# kubectl get pod
    NAME                                READY   STATUS             RESTARTS   AGE
    nginx-deployment-574b87c764-7sw2x   1/1     Running            0          3s
    nginx-deployment-574b87c764-9mnmn   1/1     Running            0          3s
    nginx-deployment-574b87c764-b6jhm   1/1     Running            0          3m36s
    nginx-deployment-574b87c764-tgsb8   1/1     Running            0          3m35s
    
    [root@k8s-01 ~]# kubectl get deployment
    NAME               READY   UP-TO-DATE   AVAILABLE   AGE
    nginx-deployment   4/4     4            4           64m

参考文章：  
[http://k8s.unixhot.com/kubernetes/deployment.html][http_k8s.unixhot.com_kubernetes_deployment.html]

[http_k8s.unixhot.com_kubernetes_deployment.html]: http://k8s.unixhot.com/kubernetes/deployment.html