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vssueId, layout, description, meta
| vssueId | layout | description | meta | |||||
|---|---|---|---|---|---|---|---|---|
| 36 | LearningLayout | 本文描述了如何在 Kubernetes 中回滚 Deployment |
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回滚 Deployment
某些情况下，您可能想要回滚（rollback）Deployment，例如：Deployment 不稳定（可能是不断地崩溃）。默认情况下，kubernetes 将保存 Deployment 的所有更新（rollout）历史。您可以设定 revision history limit 来确定保存的历史版本数量。
::: tip
当且仅当 Deployment 的 .spec.template 字段被修改时（例如，您修改了容器的镜像），kubernetes 将为其创建一个 Deployment revision（版本）。Deployment 的其他更新（例如：修改 .spec.replicas 字段）将不会创建新的 Deployment reviesion（版本）。
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本文提供了两种途径对 Deployment 执行回滚操作：
- 使用 kubectl 回滚 Deployment
- 使用 Kuboard 回滚 Deployment
模拟更新错误
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假设您在更新 Deployment 的时候，犯了一个拼写错误，将
nginx:1.9.1写成了nginx:1.91kubectl set image deployment.v1.apps/nginx-deployment nginx=nginx:1.91 --record=true输出结果如下所示：
deployment.apps/nginx-deployment image updated -
该更新将卡住，您可以执行命令
kubectl rollout status deployment.v1.apps/nginx-deployment检查其状态，输出结果如下所示：Waiting for rollout to finish: 1 out of 3 new replicas have been updated... -
执行命令
kubectl get rs您将看到两个旧的 ReplicaSet（nginx-deployment-1564180365 and nginx-deployment-2035384211）和一个新的 ReplicaSet (nginx-deployment-3066724191) 。如下所示：NAME DESIRED CURRENT READY AGE nginx-deployment-1564180365 3 3 3 25s nginx-deployment-2035384211 0 0 0 36s nginx-deployment-3066724191 1 1 0 6s -
执行命令
kubectl get pods，您将看到 1 个由新 ReplicaSet 创建的 Pod 卡在抓取 image 的死循环里：NAME READY STATUS RESTARTS AGE nginx-deployment-1564180365-70iae 1/1 Running 0 25s nginx-deployment-1564180365-jbqqo 1/1 Running 0 25s nginx-deployment-1564180365-hysrc 1/1 Running 0 25s nginx-deployment-3066724191-08mng 0/1 ImagePullBackOff 0 6s::: tip Deployment Controller 将自动停止有问题的更新（rollout），不会继续 scale up 新的 ReplicaSet。maxUnavailable 参数指定了最多会有几个 Pod 副本卡住，该参数的默认值是 25%。 :::
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执行命令
kubectl describe deployment查看 Deployment 的详情，输出结果如下所示：Name: nginx-deployment Namespace: default CreationTimestamp: Tue, 15 Mar 2016 14:48:04 -0700 Labels: app=nginx Selector: app=nginx Replicas: 3 desired | 1 updated | 4 total | 3 available | 1 unavailable StrategyType: RollingUpdate MinReadySeconds: 0 RollingUpdateStrategy: 25% max unavailable, 25% max surge Pod Template: Labels: app=nginx Containers: nginx: Image: nginx:1.91 Port: 80/TCP Host Port: 0/TCP Environment: <none> Mounts: <none> Volumes: <none> Conditions: Type Status Reason ---- ------ ------ Available True MinimumReplicasAvailable Progressing True ReplicaSetUpdated OldReplicaSets: nginx-deployment-1564180365 (3/3 replicas created) NewReplicaSet: nginx-deployment-3066724191 (1/1 replicas created) Events: FirstSeen LastSeen Count From SubobjectPath Type Reason Message --------- -------- ----- ---- ------------- -------- ------ ------- 1m 1m 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set nginx-deployment-2035384211 to 3 22s 22s 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set nginx-deployment-1564180365 to 1 22s 22s 1 {deployment-controller } Normal ScalingReplicaSet Scaled down replica set nginx-deployment-2035384211 to 2 22s 22s 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set nginx-deployment-1564180365 to 2 21s 21s 1 {deployment-controller } Normal ScalingReplicaSet Scaled down replica set nginx-deployment-2035384211 to 1 21s 21s 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set nginx-deployment-1564180365 to 3 13s 13s 1 {deployment-controller } Normal ScalingReplicaSet Scaled down replica set nginx-deployment-2035384211 to 0 13s 13s 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set nginx-deployment-3066724191 to 1为了修复这个问题，您需要将其回滚到之前的一个稳定版本。
检查 Deployment 的更新历史
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执行命令
kubectl rollout history deployment.v1.apps/nginx-deployment检查 Deployment 的历史版本，输出结果如下所示：deployments "nginx-deployment" REVISION CHANGE-CAUSE 1 kubectl apply --filename=https://k8s.io/examples/controllers/nginx-deployment.yaml --record=true 2 kubectl set image deployment.v1.apps/nginx-deployment nginx=nginx:1.9.1 --record=true 3 kubectl set image deployment.v1.apps/nginx-deployment nginx=nginx:1.91 --record=trueCHANGE-CAUSE 是该 revision（版本）创建时从 Deployment 的 annotation
kubernetes.io/change-cause拷贝而来。您可以通过如下方式制定 CHANGE-CAUSE 信息：
- 为 Deployment 增加注解，
kubectl annotate deployment.v1.apps/nginx-deployment kubernetes.io/change-cause="image updated to 1.9.1" - 执行 kubectl apply 命令时，增加
--record选项 - 手动编辑 Deployment 的
.metadata.annotation信息
- 为 Deployment 增加注解，
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执行命令
kubectl rollout history deployment.v1.apps/nginx-deployment --revision=2，查看 revision（版本）的详细信息，输出结果如下所示：deployments "nginx-deployment" revision 2 Labels: app=nginx pod-template-hash=1159050644 Annotations: kubernetes.io/change-cause=kubectl set image deployment.v1.apps/nginx-deployment nginx=nginx:1.9.1 --record=true Containers: nginx: Image: nginx:1.9.1 Port: 80/TCP QoS Tier: cpu: BestEffort memory: BestEffort Environment Variables: <none> No volumes.
回滚到前一个 revision（版本）
下面的步骤可将 Deployment 从当前版本回滚到前一个版本（version 2）
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执行命令
kubectl rollout undo deployment.v1.apps/nginx-deployment将当前版本回滚到前一个版本，输出结果如下所示：deployment.apps/nginx-deployment或者，您也可以使用
--to-revision选项回滚到前面的某一个指定版本，执行如下命令：kubectl rollout undo deployment.v1.apps/nginx-deployment --to-revision=2输出结果如下：
deployment.apps/nginx-deployment更详细的信息，请参考 kubectl rollout
此时，Deployment 已经被回滚到前一个稳定版本。您可以看到 Deployment Controller 为该 Deployment 产生了 DeploymentRollback event。
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执行命令
kubectl get deployment nginx-deployment，检查该回滚是否成功，Deployment 是否按预期的运行，输出结果如下：NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE nginx-deployment 3 3 3 3 30m -
执行命令
kubectl describe deployment nginx-deployment查看 Deployment 的详情，输出结果如下：Name: nginx-deployment Namespace: default CreationTimestamp: Sun, 02 Sep 2018 18:17:55 -0500 Labels: app=nginx Annotations: deployment.kubernetes.io/revision=4 kubernetes.io/change-cause=kubectl set image deployment.v1.apps/nginx-deployment nginx=nginx:1.9.1 --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: nginx:1.9.1 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-c4747d96c (3/3 replicas created) Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal ScalingReplicaSet 12m deployment-controller Scaled up replica set nginx-deployment-75675f5897 to 3 Normal ScalingReplicaSet 11m deployment-controller Scaled up replica set nginx-deployment-c4747d96c to 1 Normal ScalingReplicaSet 11m deployment-controller Scaled down replica set nginx-deployment-75675f5897 to 2 Normal ScalingReplicaSet 11m deployment-controller Scaled up replica set nginx-deployment-c4747d96c to 2 Normal ScalingReplicaSet 11m deployment-controller Scaled down replica set nginx-deployment-75675f5897 to 1 Normal ScalingReplicaSet 11m deployment-controller Scaled up replica set nginx-deployment-c4747d96c to 3 Normal ScalingReplicaSet 11m deployment-controller Scaled down replica set nginx-deployment-75675f5897 to 0 Normal ScalingReplicaSet 11m deployment-controller Scaled up replica set nginx-deployment-595696685f to 1 Normal DeploymentRollback 15s deployment-controller Rolled back deployment "nginx-deployment" to revision 2 Normal ScalingReplicaSet 15s deployment-controller Scaled down replica set nginx-deployment-595696685f to 0
模拟更新错误
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假设您更新 Deployment 的时候，犯了一个拼写错误，将
1.9.1写成了1.91，如下图所示：
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该更新将卡住，新的副本集中的 Pod 将因为抓取不到镜像而不能启动，并陷入不断抓取镜像的死循环当中，如下图所示：
检查 Deployment 的更新历史，并回滚
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上图中，显示了该 Deployment 有三个副本集，分别对应 Deployment 的版本
1、2、3。点击某一个副本集上的 回滚 按钮，Kuboard 将为您对比两个版本之间的差异，如下图所示：
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点击 确认回滚 按钮，将回滚到选定的版本
