86 lines
2.3 KiB
Markdown
86 lines
2.3 KiB
Markdown
# Kubernetes 201
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## 扩展应用
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通过修改Deployment中副本的数量（replicas），可以动态扩展或收缩应用：
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这些自动扩展的容器会自动加入到service中，而收缩回收的容器也会自动从service中删除。
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```sh
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$ kubectl scale --replicas=3 deployment/nginx-app
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$ kubectl get deploy
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NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
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nginx-app 3 3 3 3 10m
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```
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## 滚动升级
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滚动升级（Rolling Update）通过逐个容器替代升级的方式来实现无中断的服务升级：
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```
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kubectl rolling-update frontend-v1 frontend-v2 --image=image:v2
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```
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在滚动升级的过程中，如果发现了失败或者配置错误，还可以随时会滚回来：
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```
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kubectl rolling-update frontend-v1 frontend-v2 --rollback
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```
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需要注意的是，rolling-update只针对ReplicationController，不能直接用在deployment上。Deployment可以在spec中设置更新策略为RollingUpdate（默认就是RollingUpdate）：
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```yaml
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spec:
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replicas: 3
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selector:
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matchLabels:
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run: nginx-app
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strategy:
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rollingUpdate:
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maxSurge: 1
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maxUnavailable: 1
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type: RollingUpdate
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```
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而更新应用的话，就可以直接用`kubectl set`命令：
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```sh
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kubectl set image deployment/nginx-app nginx-app=nginx:1.9.1
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```
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滚动升级的过程可以用`rollout`命令查看:
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```sh
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$ kubectl rollout status deployment/nginx-app
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Waiting for rollout to finish: 2 out of 3 new replicas have been updated...
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Waiting for rollout to finish: 2 of 3 updated replicas are available...
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Waiting for rollout to finish: 2 of 3 updated replicas are available...
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Waiting for rollout to finish: 2 of 3 updated replicas are available...
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Waiting for rollout to finish: 2 of 3 updated replicas are available...
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Waiting for rollout to finish: 2 of 3 updated replicas are available...
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deployment "nginx-app" successfully rolled out
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```
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Deployment同样支持回滚：
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```sh
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$ kubectl rollout history deployment/nginx-app
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deployments "nginx-app"
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REVISION CHANGE-CAUSE
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1 <none>
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2 <none>
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$ kubernetes kubectl rollout undo deployment/nginx-app
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deployment "nginx-app" rolled back
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```
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