Kubernetes K8S之资源控制器RC、RS、Deployment详解

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Kubernetes的资源控制器ReplicationController（RC）、ReplicaSet（RS）、Deployment（Deploy）详解与示例

主机配置规划

服务器名称(hostname) 系统版本 配置 内网IP 外网IP(模拟)
k8s-master CentOS7.7 2C/4G/20G 172.16.1.110 10.0.0.110
k8s-node01 CentOS7.7 2C/4G/20G 172.16.1.111 10.0.0.111
k8s-node02 CentOS7.7 2C/4G/20G 172.16.1.112 10.0.0.112

什么是控制器

kubernetes中内建了很多controller（控制器），这些相当于一个状态机，用来控制pod的具体状态和行为。

部分控制器类型如下：
  • ReplicationController 和 ReplicaSet
  • Deployment
  • DaemonSet
  • StatefulSet
  • Job/CronJob
  • HorizontalPodAutoscaler

ReplicationController 和 ReplicaSet

ReplicationController (RC)用来确保容器应用的副本数始终保持在用户定义的副本数，即如果有容器异常退出，会自动创建新的pod来替代；而异常多出来的容器也会自动回收。

在新版的Kubernetes中建议使用ReplicaSet (RS)来取代ReplicationController。ReplicaSet跟ReplicationController没有本质的不同，只是名字不一样，但ReplicaSet支持集合式selector。

虽然 ReplicaSets 可以独立使用，但如今它主要被Deployments 用作协调 Pod 的创建、删除和更新的机制。当使用 Deployment 时，你不必担心还要管理它们创建的 ReplicaSet，Deployment 会拥有并管理它们的 ReplicaSet。

ReplicaSet 是下一代的 Replication Controller。 ReplicaSet 和 Replication Controller 的唯一区别是选择器的支持。ReplicaSet 支持新的基于集合的选择器需求，这在标签用户指南中有描述。而 Replication Controller 仅支持基于相等选择器的需求。

Deployments

Deployment 控制器为 Pods和 ReplicaSets提供描述性的更新方式。用来替代以前的ReplicationController以方便管理应用。

典型的应用场景包括：
  • 定义Deployment来创建Pod和ReplicaSet
  • 滚动升级和回滚应用
  • 扩容和缩容
  • 暂停和继续Deployment

ReplicaSet示例

yaml文件

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[root@k8s-master controller]# pwd
/root/k8s_practice/controller
[root@k8s-master controller]# cat ReplicaSet-01.yaml 
apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: frontend
spec:
  replicas: 3
  selector:
    matchLabels:
      tier: frontend
  template:
    metadata:
      labels:
        tier: frontend
    spec:
      containers:
      - name: nginx
        image: registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17
        imagePullPolicy: IfNotPresent
        ports:
        - name: httpd
          containerPort: 80

创建ReplicaSet，并查看rs状态与详情

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[root@k8s-master controller]# kubectl apply -f ReplicaSet-01.yaml 
replicaset.apps/frontend created
[root@k8s-master controller]# kubectl get rs -o wide    # 查看状态
NAME       DESIRED   CURRENT   READY   AGE     CONTAINERS   IMAGES                                                        SELECTOR
frontend   3         3         3       2m12s   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17   tier=frontend
[root@k8s-master controller]# 
[root@k8s-master controller]# kubectl describe rs frontend   # 查看详情
Name:         frontend
Namespace:    default
Selector:     tier=frontend
Labels:       <none>
Annotations:  kubectl.kubernetes.io/last-applied-configuration:
                {"apiVersion":"apps/v1","kind":"ReplicaSet","metadata":{"annotations":{},"name":"frontend","namespace":"default"},"spec":{"replicas":3,"se...
Replicas:     3 current / 3 desired
Pods Status:  3 Running / 0 Waiting / 0 Succeeded / 0 Failed
Pod Template:
  Labels:  tier=frontend
  Containers:
   nginx:
    Image:        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17
    Port:         80/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Events:
  Type    Reason            Age    From                   Message
  ----    ------            ----   ----                   -------
  Normal  SuccessfulCreate  10m    replicaset-controller  Created pod: frontend-kltwp
  Normal  SuccessfulCreate  10m    replicaset-controller  Created pod: frontend-76dbn
  Normal  SuccessfulCreate  10m    replicaset-controller  Created pod: frontend-jk8td

查看pod状态信息

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[root@k8s-master controller]# kubectl get pod -o wide --show-labels
NAME             READY   STATUS    RESTARTS   AGE     IP            NODE         NOMINATED NODE   READINESS GATES   LABELS
frontend-76dbn   1/1     Running   0          5m15s   10.244.4.31   k8s-node01   <none>           <none>            tier=frontend
frontend-jk8td   1/1     Running   0          5m15s   10.244.2.35   k8s-node02   <none>           <none>            tier=frontend
frontend-kltwp   1/1     Running   0          5m15s   10.244.2.34   k8s-node02   <none>           <none>            tier=frontend

删除一个pod，然后再次查看

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[root@k8s-master controller]# kubectl delete pod frontend-kltwp
pod "frontend-kltwp" deleted
[root@k8s-master controller]# 
[root@k8s-master controller]# kubectl get pod -o wide --show-labels   # 可见重新创建了一个pod
NAME             READY   STATUS    RESTARTS   AGE     IP            NODE         NOMINATED NODE   READINESS GATES   LABELS
frontend-76dbn   1/1     Running   0          7m27s   10.244.4.31   k8s-node01   <none>           <none>            tier=frontend
frontend-jk8td   1/1     Running   0          7m27s   10.244.2.35   k8s-node02   <none>           <none>            tier=frontend
frontend-mf79k   1/1     Running   0          16s     10.244.4.32   k8s-node01   <none>           <none>            tier=frontend

由上可见，rs又新建了一个pod，保证了pod数总是为3.

Deployment示例

创建 Deployment

yaml文件

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[root@k8s-master controller]# pwd
/root/k8s_practice/controller
[root@k8s-master controller]# cat nginx-deployment-1.17.1.yaml 
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 3
  # 重点关注该字段
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.1
        ports:
        - containerPort: 80
[root@k8s-master controller]# 
[root@k8s-master controller]# cat nginx-deployment-1.17.5.yaml 
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 3
  # 重点关注该字段
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.5
        ports:
        - containerPort: 80

selector 字段定义 Deployment 如何查找要管理的 Pods。 在这种情况下，会选择在 template（Pod）模板中定义的标签labels（app: nginx）。但更复杂的选择规则是可能的，只要 template （Pod） 模板本身满足规则。

刚启动时状态说明

启动deployment，并查看状态

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[root@k8s-master controller]# kubectl apply -f nginx-deployment-1.17.1.yaml --record
deployment.apps/nginx-deployment created
[root@k8s-master controller]# 
[root@k8s-master controller]# kubectl get deployment -o wide
NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES                                                          SELECTOR
nginx-deployment   2/3     3            2           10s   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.1   app=nginx

# --record 参数可以记录命令，通过 kubectl rollout history deployment/nginx-deployment 可查询

参数说明：

  • NAME：列出集群中 Deployments 的名称
  • READY：已就绪副本数/期望副本数
  • UP-TO-DATE：显示已更新和正在更新中的副本数
  • AVAILABLE：显示应用程序可供用户使用的副本数
  • AGE：显示运行的时间

查看ReplicaSet状态

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[root@k8s-master controller]# kubectl get rs -o wide
NAME                          DESIRED   CURRENT   READY   AGE   CONTAINERS   IMAGES                                                          SELECTOR
nginx-deployment-76b9d6bcf5   3         3         2       17s   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.1   app=nginx,pod-template-hash=76b9d6bcf5

参数说明：

  • NAME：列出集群中 ReplicaSet的名称
  • DESIRED：期望副本数
  • CURRENT：当前副本数
  • READY：已就绪副本数
  • AGE：运行时间

查看pod状态

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[root@k8s-master controller]# kubectl get pod -o wide
NAME                                READY   STATUS              RESTARTS   AGE   IP            NODE         NOMINATED NODE   READINESS GATES
nginx-deployment-76b9d6bcf5-ngpg5   1/1     Running             0          26s   10.244.2.43   k8s-node02   <none>           <none>
nginx-deployment-76b9d6bcf5-rw827   1/1     Running             0          26s   10.244.2.44   k8s-node02   <none>           <none>
nginx-deployment-76b9d6bcf5-ttf4j   0/1     ContainerCreating   0          26s   <none>        k8s-node01   <none>           <none>
过一会儿状态说明
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[root@k8s-master controller]# kubectl get deployment -o wide --show-labels
NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES                                                          SELECTOR    LABELS
nginx-deployment   3/3     3            3           23m   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.1   app=nginx   app=nginx
[root@k8s-master controller]# 
[root@k8s-master controller]# kubectl get rs -o wide --show-labels
NAME                          DESIRED   CURRENT   READY   AGE   CONTAINERS   IMAGES                                                          SELECTOR                                 LABELS
nginx-deployment-76b9d6bcf5   3         3         3       23m   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.1   app=nginx,pod-template-hash=76b9d6bcf5   app=nginx,pod-template-hash=76b9d6bcf5
[root@k8s-master controller]# 
[root@k8s-master controller]# kubectl get pod -o wide --show-labels
NAME                                READY   STATUS    RESTARTS   AGE   IP            NODE         NOMINATED NODE   READINESS GATES   LABELS
nginx-deployment-76b9d6bcf5-ngpg5   1/1     Running   0          23m   10.244.2.43   k8s-node02   <none>           <none>            app=nginx,pod-template-hash=76b9d6bcf5
nginx-deployment-76b9d6bcf5-rw827   1/1     Running   0          23m   10.244.2.44   k8s-node02   <none>           <none>            app=nginx,pod-template-hash=76b9d6bcf5
nginx-deployment-76b9d6bcf5-ttf4j   1/1     Running   0          23m   10.244.4.37   k8s-node01   <none>           <none>            app=nginx,pod-template-hash=76b9d6bcf5
重点说明

1、ReplicaSet 的名称始终被格式化为[DEPLOYMENT-NAME]-[RANDOM-STRING]。随机字符串是随机生成，并使用 pod-template-hash 作为选择器和标签。

2、Deployment 控制器将 pod-template-hash 标签添加到 Deployment 创建或使用的每个 ReplicaSet 。此标签可确保 Deployment 的子 ReplicaSets 不重叠。因此不可修改。

3、注意Deployment、ReplicaSet和Pod三者的名称关系

更新 Deployment

Deployment 可确保在更新时仅关闭一定数量的 Pods。默认情况下，它确保至少 75%所需 Pods 运行（25%最大不可用）。

Deployment 更新过程中还确保仅创建一定数量的 Pods 且高于期望的 Pods 数。默认情况下，它可确保最多增加 25% 期望 Pods 数（25%最大增量）。

备注：实际操作中如果更新Deployment，那么最好通过yaml文件更新，这样回滚到任何版本都非常便捷，而且更容易追述；而不是通过命令行。

如下Deployment示例，由于只有3个副本。因此更新时不会先删除旧的pod，而是先新建一个pod。新pod运行时，才会删除对应老的pod。一切的前提都是为了满足上述的条件。

需求：更新 nginx Pods，从当前的1.17.1版本改为1.17.5版本。

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# 方式一
kubectl edit deployment/nginx-deployment    # 然后修改 image 镜像信息 【不推荐】
# 上述方法不会记录命令，通过kubectl rollout history deployment/nginx-deployment 无法查询

# 方式二如下【可使用】：
kubectl set image deployment/nginx-deployment nginx=registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.5 --record 

# 方式三如下【推荐★★★★★】
kubectl apply -f nginx-deployment-1.17.5.yaml --record

# --record 参数可以记录命令，通过 kubectl rollout history deployment/nginx-deployment 可查询

要查看更新状态

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[root@k8s-master controller]# kubectl rollout status deployment/nginx-deployment
# 如没有更新完成，则显示更新过程直到更新成功
Waiting for deployment "nginx-deployment" rollout to finish: 1 out of 3 new replicas have been updated...
Waiting for deployment "nginx-deployment" rollout to finish: 1 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: 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
# 如已更新完毕，直接显示更新成功
deployment "nginx-deployment" successfully rolled out
更新中的Deployment、ReplicaSet、Pod信息
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[root@k8s-master controller]# kubectl get deployment -o wide --show-labels
NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES                                                          SELECTOR    LABELS
nginx-deployment   3/3     1            3           12m   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.5   app=nginx   app=nginx
[root@k8s-master controller]# 
[root@k8s-master controller]# kubectl get rs -o wide --show-labels
NAME                          DESIRED   CURRENT   READY   AGE   CONTAINERS   IMAGES                                                          SELECTOR                                 LABELS
nginx-deployment-56d78686f5   1         1         0       23s   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.5   app=nginx,pod-template-hash=56d78686f5   app=nginx,pod-template-hash=56d78686f5
nginx-deployment-76b9d6bcf5   3         3         3       12m   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.1   app=nginx,pod-template-hash=76b9d6bcf5   app=nginx,pod-template-hash=76b9d6bcf5
[root@k8s-master controller]# 
[root@k8s-master controller]# kubectl get pod -o wide --show-labels
NAME                                READY   STATUS              RESTARTS   AGE   IP            NODE         NOMINATED NODE   READINESS GATES   LABELS
nginx-deployment-56d78686f5-4kn4c   0/1     ContainerCreating   0          30s   <none>        k8s-node02   <none>           <none>            app=nginx,pod-template-hash=56d78686f5
nginx-deployment-76b9d6bcf5-7lcr9   1/1     Running             0          12m   10.244.4.41   k8s-node01   <none>           <none>            app=nginx,pod-template-hash=76b9d6bcf5
nginx-deployment-76b9d6bcf5-jbb5h   1/1     Running             0          12m   10.244.2.48   k8s-node02   <none>           <none>            app=nginx,pod-template-hash=76b9d6bcf5
nginx-deployment-76b9d6bcf5-rt4m7   1/1     Running             0          12m   10.244.4.42   k8s-node01   <none>           <none>            app=nginx,pod-template-hash=76b9d6bcf5
更新成功后的Deployment、ReplicaSet、Pod信息
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[root@k8s-master controller]# kubectl get deployment -o wide --show-labels
NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES                                                          SELECTOR    LABELS
nginx-deployment   3/3     3            3           15m   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.5   app=nginx   app=nginx
[root@k8s-master controller]# 
[root@k8s-master controller]# kubectl get rs -o wide --show-labels
NAME                          DESIRED   CURRENT   READY   AGE     CONTAINERS   IMAGES                                                          SELECTOR                                 LABELS
nginx-deployment-56d78686f5   3         3         3       3m23s   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.5   app=nginx,pod-template-hash=56d78686f5   app=nginx,pod-template-hash=56d78686f5
nginx-deployment-76b9d6bcf5   0         0         0       15m     nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.1   app=nginx,pod-template-hash=76b9d6bcf5   app=nginx,pod-template-hash=76b9d6bcf5
[root@k8s-master controller]# 
[root@k8s-master controller]# kubectl get pod -o wide --show-labels
NAME                                READY   STATUS    RESTARTS   AGE     IP            NODE         NOMINATED NODE   READINESS GATES   LABELS
nginx-deployment-56d78686f5-4kn4c   1/1     Running   0          3m25s   10.244.2.49   k8s-node02   <none>           <none>            app=nginx,pod-template-hash=56d78686f5
nginx-deployment-56d78686f5-khsnm   1/1     Running   0          100s    10.244.2.50   k8s-node02   <none>           <none>            app=nginx,pod-template-hash=56d78686f5
nginx-deployment-56d78686f5-t24qw   1/1     Running   0          2m44s   10.244.4.43   k8s-node01   <none>           <none>            app=nginx,pod-template-hash=56d78686f5

通过查询Deployment详情，知晓pod替换过程

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[root@k8s-master controller]# kubectl describe deploy nginx-deployment
Name:                   nginx-deployment
Namespace:              default
CreationTimestamp:      Thu, 28 May 2020 00:04:09 +0800
Labels:                 app=nginx
Annotations:            deployment.kubernetes.io/revision: 2
                        kubectl.kubernetes.io/last-applied-configuration:
                          {"apiVersion":"apps/v1","kind":"Deployment","metadata":{"annotations":{"kubernetes.io/change-cause":"kubectl apply --filename=nginx-deploy...
                        kubernetes.io/change-cause:
                          kubectl set image deployment/nginx-deployment nginx=registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.5 --record=true
Selector:               app=nginx
Replicas:               3 desired | 3 updated | 3 total | 3 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  app=nginx
  Containers:
   nginx:
    Image:        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.5
    Port:         80/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
  Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  <none>
NewReplicaSet:   nginx-deployment-56d78686f5 (3/3 replicas created)
Events:
  Type    Reason             Age   From                   Message
  ----    ------             ----  ----                   -------
  Normal  ScalingReplicaSet  93s   deployment-controller  Scaled up replica set nginx-deployment-76b9d6bcf5 to 3
  Normal  ScalingReplicaSet  38s   deployment-controller  Scaled up replica set nginx-deployment-56d78686f5 to 1
  Normal  ScalingReplicaSet  37s   deployment-controller  Scaled down replica set nginx-deployment-76b9d6bcf5 to 2
  Normal  ScalingReplicaSet  37s   deployment-controller  Scaled up replica set nginx-deployment-56d78686f5 to 2
  Normal  ScalingReplicaSet  35s   deployment-controller  Scaled down replica set nginx-deployment-76b9d6bcf5 to 1
  Normal  ScalingReplicaSet  35s   deployment-controller  Scaled up replica set nginx-deployment-56d78686f5 to 3
  Normal  ScalingReplicaSet  34s   deployment-controller  Scaled down replica set nginx-deployment-76b9d6bcf5 to 0

多 Deployment 动态更新

当 Deployment 正在展开进行更新时，Deployment 会为每个更新创建一个新的 ReplicaSet 并开始向上扩展，之前的 ReplicaSet 会被添加到旧 ReplicaSets 队列并开始向下扩展。

例如，假设创建一个 Deployment 以创建 nginx:1.7.9 的 5 个副本，然后更新 Deployment 以创建 5 个 nginx:1.9.1 的副本，而此时只有 3 个nginx:1.7.9 的副本已创建。在这种情况下， Deployment 会立即开始杀死3个 nginx:1.7.9 Pods，并开始创建 nginx:1.9.1 Pods。它不等待 nginx:1.7.9 的 5 个副本完成后再更新为nginx:1.9.1。

回滚 Deployment

yaml文件方式

针对应用的每个镜像版本，都有对应deploy的yaml文件。不管是升级还是回滚都已轻松应对。如下

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nginx-deployment-1.15.6.yaml
nginx-deployment-1.17.yaml
nginx-deployment-1.17.1.yaml
nginx-deployment-1.17.5.yaml

yaml文件中的信息，参考上文即可。

命令行方式

问题产生

假设在更新 Deployment 时犯了一个拼写错误，将镜像名称命名为了 nginx:1.1710 而不是 nginx:1.17.10

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[root@k8s-master controller]# kubectl set image deployment/nginx-deployment nginx=registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.1710 --record
deployment.apps/nginx-deployment image updated

查看Deployment、ReplicaSet、Pod信息

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[root@k8s-master controller]# kubectl get deploy -o wide --show-labels
NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES                                                          SELECTOR    LABELS
nginx-deployment   3/3     1            3           14m   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.1710   app=nginx   app=nginx
[root@k8s-master controller]#
[root@k8s-master controller]# kubectl get rs -o wide --show-labels
NAME                          DESIRED   CURRENT   READY   AGE     CONTAINERS   IMAGES                                                          SELECTOR                                 LABELS
nginx-deployment-55c7bdfb86   3         3         3       9m19s   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17     app=nginx,pod-template-hash=55c7bdfb86   app=nginx,pod-template-hash=55c7bdfb86
nginx-deployment-56d78686f5   0         0         0       12m     nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.5   app=nginx,pod-template-hash=56d78686f5   app=nginx,pod-template-hash=56d78686f5
nginx-deployment-76b9d6bcf5   0         0         0       13m     nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.1   app=nginx,pod-template-hash=76b9d6bcf5   app=nginx,pod-template-hash=76b9d6bcf5
nginx-deployment-844d7bbb7f   1         1         0       64s     nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.1710   app=nginx,pod-template-hash=844d7bbb7f   app=nginx,pod-template-hash=844d7bbb7f
[root@k8s-master controller]#
[root@k8s-master controller]# kubectl get pod -o wide --show-labels
NAME                                READY   STATUS             RESTARTS   AGE    IP            NODE         NOMINATED NODE   READINESS GATES   LABELS
nginx-deployment-55c7bdfb86-bwzk9   1/1     Running            0          10m    10.244.4.49   k8s-node01   <none>           <none>            app=nginx,pod-template-hash=55c7bdfb86
nginx-deployment-55c7bdfb86-cmvzg   1/1     Running            0          10m    10.244.2.55   k8s-node02   <none>           <none>            app=nginx,pod-template-hash=55c7bdfb86
nginx-deployment-55c7bdfb86-kjrrw   1/1     Running            0          10m    10.244.2.56   k8s-node02   <none>           <none>            app=nginx,pod-template-hash=55c7bdfb86
nginx-deployment-844d7bbb7f-pctwr   0/1     ImagePullBackOff   0          2m3s   10.244.4.51   k8s-node01   <none>           <none>            app=nginx,pod-template-hash=844d7bbb7f
需求：回滚到以前稳定的 Deployment 版本。

操作步骤如下：

检查 Deployment 修改历史

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[root@k8s-master controller]# kubectl rollout history deployment/nginx-deployment
deployment.apps/nginx-deployment 
REVISION  CHANGE-CAUSE
1         kubectl apply --filename=nginx-deployment.yaml --record=true
2         kubectl set image deployment/nginx-deployment nginx=registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.5 --record=true
3         kubectl set image deployment/nginx-deployment nginx=registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17 --record=true
4         kubectl set image deployment/nginx-deployment nginx=registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.1710 --record=true

查看修改历史的详细信息，运行

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[root@k8s-master controller]# kubectl rollout history deployment/nginx-deployment --revision=3
deployment.apps/nginx-deployment with revision #3
Pod Template:
  Labels:	app=nginx
	pod-template-hash=55c7bdfb86
  Annotations:	kubernetes.io/change-cause:
	  kubectl set image deployment/nginx-deployment nginx=registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17 --record=true
  Containers:
   nginx:
    Image:	registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17
    Port:	80/TCP
    Host Port:	0/TCP
    Environment:	<none>
    Mounts:	<none>
  Volumes:	<none>

回滚到上一次修改（即版本 3）或指定版本

现在已决定撤消当前更新并回滚到以前的版本

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# 回滚到上一版本
[root@k8s-master controller]# kubectl rollout undo deployment/nginx-deployment
deployment.apps/nginx-deployment rolled back
# 回滚到指定历史版本
[root@k8s-master controller]# kubectl rollout undo deployment/nginx-deployment --to-revision=2
deployment.apps/nginx-deployment rolled back

检查回滚是否成功、 Deployment 是否正在运行

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[root@k8s-master controller]# kubectl get deploy -o wide --show-labels
NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES                                                          SELECTOR    LABELS
nginx-deployment   3/3     3            3           17h   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.5   app=nginx   app=nginx

获取 Deployment 描述信息

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[root@k8s-master controller]# kubectl describe deployment
Name:                   nginx-deployment
Namespace:              default
CreationTimestamp:      Thu, 28 May 2020 00:04:09 +0800
Labels:                 app=nginx
Annotations:            deployment.kubernetes.io/revision: 7
                        kubectl.kubernetes.io/last-applied-configuration:
                          {"apiVersion":"apps/v1","kind":"Deployment","metadata":{"annotations":{"kubernetes.io/change-cause":"kubectl apply --filename=nginx-deploy...
                        kubernetes.io/change-cause:
                          kubectl set image deployment/nginx-deployment nginx=registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.5 --record=true
Selector:               app=nginx
Replicas:               3 desired | 3 updated | 3 total | 3 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  app=nginx
  Containers:
   nginx:
    Image:        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.5
    Port:         80/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
  Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  <none>
NewReplicaSet:   nginx-deployment-56d78686f5 (3/3 replicas created)
Events:
  Type    Reason             Age                 From                   Message
  ----    ------             ----                ----                   -------
………………
  Normal  ScalingReplicaSet  107s                deployment-controller  Scaled up replica set nginx-deployment-56d78686f5 to 1
  Normal  ScalingReplicaSet  104s                deployment-controller  Scaled down replica set nginx-deployment-55c7bdfb86 to 2
  Normal  ScalingReplicaSet  104s                deployment-controller  Scaled up replica set nginx-deployment-56d78686f5 to 2
  Normal  ScalingReplicaSet  103s                deployment-controller  Scaled down replica set nginx-deployment-55c7bdfb86 to 1
  Normal  ScalingReplicaSet  103s                deployment-controller  Scaled up replica set nginx-deployment-56d78686f5 to 3
  Normal  ScalingReplicaSet  102s                deployment-controller  Scaled down replica set nginx-deployment-55c7bdfb86 to 0

扩容/缩容Deployment

操作过程如下

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[root@k8s-master controller]# kubectl scale deployment/nginx-deployment --replicas=10
deployment.apps/nginx-deployment scaled
[root@k8s-master controller]# kubectl get deploy -o wide --show-labels
NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES                                                          SELECTOR    LABELS
nginx-deployment   10/10   10           10          17h   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.5   app=nginx   app=nginx
[root@k8s-master controller]# 
[root@k8s-master controller]# kubectl get rs -o wide --show-labels
NAME                          DESIRED   CURRENT   READY   AGE   CONTAINERS   IMAGES                                                          SELECTOR                                 LABELS
nginx-deployment-55c7bdfb86   0         0         0       17h   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17     app=nginx,pod-template-hash=55c7bdfb86   app=nginx,pod-template-hash=55c7bdfb86
nginx-deployment-56d78686f5   10        10        10      17h   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.5   app=nginx,pod-template-hash=56d78686f5   app=nginx,pod-template-hash=56d78686f5
nginx-deployment-76b9d6bcf5   0         0         0       17h   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.17.1   app=nginx,pod-template-hash=76b9d6bcf5   app=nginx,pod-template-hash=76b9d6bcf5
nginx-deployment-844d7bbb7f   0         0         0       17h   nginx        registry.cn-beijing.aliyuncs.com/google_registry/nginx:1.1710   app=nginx,pod-template-hash=844d7bbb7f   app=nginx,pod-template-hash=844d7bbb7f
[root@k8s-master controller]# 
[root@k8s-master controller]# kubectl get pod -o wide --show-labels
NAME                                READY   STATUS    RESTARTS   AGE   IP            NODE         NOMINATED NODE   READINESS GATES   LABELS
nginx-deployment-56d78686f5-4v5mj   1/1     Running   0          44s   10.244.2.64   k8s-node02   <none>           <none>            app=nginx,pod-template-hash=56d78686f5
nginx-deployment-56d78686f5-8m7mx   1/1     Running   0          44s   10.244.4.60   k8s-node01   <none>           <none>            app=nginx,pod-template-hash=56d78686f5
nginx-deployment-56d78686f5-c7wlb   1/1     Running   0          44s   10.244.4.59   k8s-node01   <none>           <none>            app=nginx,pod-template-hash=56d78686f5
nginx-deployment-56d78686f5-jg5lt   1/1     Running   0          44s   10.244.2.63   k8s-node02   <none>           <none>            app=nginx,pod-template-hash=56d78686f5
nginx-deployment-56d78686f5-jj58d   1/1     Running   0          11m   10.244.4.56   k8s-node01   <none>           <none>            app=nginx,pod-template-hash=56d78686f5
nginx-deployment-56d78686f5-k2kts   1/1     Running   0          11m   10.244.4.57   k8s-node01   <none>           <none>            app=nginx,pod-template-hash=56d78686f5
nginx-deployment-56d78686f5-qltkv   1/1     Running   0          44s   10.244.2.61   k8s-node02   <none>           <none>            app=nginx,pod-template-hash=56d78686f5
nginx-deployment-56d78686f5-r7vmm   1/1     Running   0          11m   10.244.2.60   k8s-node02   <none>           <none>            app=nginx,pod-template-hash=56d78686f5
nginx-deployment-56d78686f5-rxlpm   1/1     Running   0          44s   10.244.2.62   k8s-node02   <none>           <none>            app=nginx,pod-template-hash=56d78686f5
nginx-deployment-56d78686f5-vlzrf   1/1     Running   0          44s   10.244.4.58   k8s-node01   <none>           <none>            app=nginx,pod-template-hash=56d78686f5

清理策略Policy

可以在 Deployment 中设置 .spec.revisionHistoryLimit，以指定保留多少该 Deployment 的 ReplicaSets数量。其余的将在后台进行垃圾回收。默认情况下，是10。

注意：此字段设置为 0 将导致清理 Deployment 的所有历史记录，因此 Deployment 将无法通过命令行回滚。

相关阅读

1、Kubernetes K8S之kubectl命令详解及常用示例

完毕！

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