K8S实践Ⅲ（Pod控制器）

一、Deployment

Deployment的主要功能就是自动部署一个容器应用的多份副本，以及持续监控副本的数量，在集群内始终维持用户指定的副本数量

1.配置参数

Selector（选择器）：
　　.spec.selector是可选字段，用来指定 label selector ，圈定Deployment管理的pod范围。如果被指定， .spec.selector 必须匹配 .spec.template.metadata.labels，否则它将被API拒绝。如果 .spec.selector 没有被指定， .spec.selector.matchLabels 默认是.spec.template.metadata.labels。

2.Deployment配置实例

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
        app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.7.9
        ports:
        - containerPort: 80

# kubectl get deploy
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   3/3     3            3           58s

# kubectl get pods
NAME                               READY   STATUS             RESTARTS   AGE
liveness-http                      0/1     CrashLoopBackOff   473        28h
nginx-deployment-6dd86d77d-6hk7w   1/1     Running            0          71s
nginx-deployment-6dd86d77d-mxr8l   1/1     Running            0          71s
nginx-deployment-6dd86d77d-xxhpd   1/1     Running            0          71s

# kubectl get pods --show-labels
NAME                               READY   STATUS    RESTARTS   AGE    LABELS
nginx-deployment-6dd86d77d-6hk7w   1/1     Running   0          2m5s   app=nginx,pod-template-hash=6dd86d77d
nginx-deployment-6dd86d77d-mxr8l   1/1     Running   0          2m5s   app=nginx,pod-template-hash=6dd86d77d
nginx-deployment-6dd86d77d-xxhpd   1/1     Running   0          2m5s   app=nginx,pod-template-hash=6dd86d77d

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

3.Deployment更新升级

现将nginx镜像更新为1.9.1版本，可以通过kubectl set image命令为Deployment设置新的镜像版本

# kubectl set image deployment/nginx-deployment nginx=nginx:1.9.1
deployment.extensions/nginx-deployment image updated

# kubectl rollout status deployment/nginx-deployment
Waiting for deployment "nginx-deployment" rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for deployment "nginx-deployment" rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for deployment "nginx-deployment" rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for deployment "nginx-deployment" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "nginx-deployment" rollout to finish: 1 old replicas are pending termination...
deployment "nginx-deployment" successfully rolled out

# kubectl get rs
NAME                          DESIRED   CURRENT   READY   AGE
nginx-deployment-6dd86d77d    0         0         0       70m
nginx-deployment-784b7cc96d   3         3         3       21m

# kubectl get pod
NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-784b7cc96d-4575d   1/1     Running   0          2m13s
nginx-deployment-784b7cc96d-c98s8   1/1     Running   0          91s
nginx-deployment-784b7cc96d-r6sm9   1/1     Running   0          2m51s
#此处名称已经更新

查看Deployment详细信息

# kubectl describe deployment/nginx-deployment
Events:
  Type    Reason             Age   From                   Message
  ----    ------             ----  ----                   -------
  Normal  ScalingReplicaSet  17m   deployment-controller  Scaled up replica set nginx-deployment-784b7cc96d to 1
  Normal  ScalingReplicaSet  17m   deployment-controller  Scaled down replica set nginx-deployment-6dd86d77d to 2
  Normal  ScalingReplicaSet  17m   deployment-controller  Scaled up replica set nginx-deployment-784b7cc96d to 2
  Normal  ScalingReplicaSet  16m   deployment-controller  Scaled down replica set nginx-deployment-6dd86d77d to 1
  Normal  ScalingReplicaSet  16m   deployment-controller  Scaled up replica set nginx-deployment-784b7cc96d to 3
  Normal  ScalingReplicaSet  16m   deployment-controller  Scaled down replica set nginx-deployment-6dd86d77d to 0

另一种更新方法是使用kubectl edit命令修改 Deployment配置：
#kubectl edit deployment/nginx-deployment

4.Deployment版本回滚
查看deployment升级记录

# kubectl rollout history deployment/nginx-deployment
deployment.extensions/nginx-deployment 
REVISION  CHANGE-CAUSE
1         <none>
2         <none>

• 默认情况下，kubernetes 会在系统中保存前两次 Deployment 的 rollout 历史记录，可以修改revision history limit来更改保存的revision数。
• 这里在创建Deployment时没有增加--record参数，所以并不能看到revision的变化。在创建 Deployment 的时候加上--record参数就可以看到每个版本使用的命令。
• Deployment的更新操作是在进行rollout时触发的，这意味着当且仅当 Deployment 的 Pod template（如.spec.template）被更改时才会创建新的revision，其他的更新操作（增加副本数）将不会触发Deployment的更新操作，这意味着当回滚到之前的版本时，只有 Deployment 中的 Pod template 部分才会回退。

查看特点版本的详细信息

# kubectl rollout history deployment/nginx-deployment --revision=2

回滚至上一个版本

# kubectl rollout undo deployment/nginx-deployment
deployment.extensions/nginx-deployment rolled back

也可以使用--to-revision参数指定某个历史版本

# kubectl rollout undo deployment/nginx-deployment --to-revision=2
deployment.extensions/nginx-deployment rolled back

5.Deployment暂停和恢复