通过修改 Deployment 中副本的数量(replicas),可以动态扩展或收缩应用:
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。
$ kubectl scale --replicas=3 deployment/nginx-app$ kubectl get deployNAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGEnginx-app 3 3 3 3 10m
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:
kubectl rolling-update frontend-v1 frontend-v2 --image=image:v2
在滚动升级的过程中,如果发现了失败或者配置错误,还可以随时回滚:
kubectl rolling-update frontend-v1 frontend-v2 --rollback
需要注意的是,kubectl rolling-update
只针对 ReplicationController。对于更新策略是 RollingUpdate 的 Deployment(Deployment 可以在 spec 中设置更新策略为 RollingUpdate,默认就是 RollingUpdate),更新应用后会自动滚动升级:
spec:replicas: 3selector:matchLabels:run: nginx-appstrategy:rollingUpdate:maxSurge: 1maxUnavailable: 1type: RollingUpdate
而更新应用的话,就可以直接用 kubectl set
命令:
kubectl set image deployment/nginx-app nginx-app=nginx:1.9.1
滚动升级的过程可以用 rollout
命令查看:
$ kubectl rollout status deployment/nginx-appWaiting for rollout to finish: 2 out of 3 new replicas have been updated...Waiting for rollout to finish: 2 of 3 updated replicas are available...Waiting for rollout to finish: 2 of 3 updated replicas are available...Waiting for rollout to finish: 2 of 3 updated replicas are available...Waiting for rollout to finish: 2 of 3 updated replicas are available...Waiting for rollout to finish: 2 of 3 updated replicas are available...deployment "nginx-app" successfully rolled out
Deployment 也支持回滚:
$ kubectl rollout history deployment/nginx-appdeployments "nginx-app"REVISION CHANGE-CAUSE1 <none>2 <none>$ kubectl rollout undo deployment/nginx-appdeployment "nginx-app" rolled back
Kubernetes 通过 cgroups 提供容器资源管理的功能,可以限制每个容器的 CPU 和内存使用,比如对于刚才创建的 deployment,可以通过下面的命令限制 nginx 容器最多只用 50% 的 CPU 和 128MB 的内存:
$ kubectl set resources deployment nginx-app -c=nginx --limits=cpu=500m,memory=128Mideployment "nginx" resource requirements updated
这等同于在每个 Pod 中设置 resources limits:
apiVersion: v1kind: Podmetadata:labels:app: nginxname: nginxspec:containers:- image: nginxname: nginxresources:limits:cpu: "500m"memory: "128Mi"
Kubernetes 作为一个面向应用的集群管理工具,需要确保容器在部署后确实处在正常的运行状态。Kubernetes 提供了两种探针(Probe,支持 exec、tcpSocket 和 http 方式)来探测容器的状态:
LivenessProbe:探测应用是否处于健康状态,如果不健康则删除并重新创建容器
ReadinessProbe:探测应用是否启动完成并且处于正常服务状态,如果不正常则不会接收来自 Kubernetes Service 的流量
对于已经部署的 deployment,可以通过 kubectl edit deployment/nginx-app
来更新 manifest,增加健康检查部分:
apiVersion: extensions/v1beta1kind: Deploymentmetadata:labels:app: nginxname: nginx-defaultspec:replicas: 3selector:matchLabels:app: nginxtemplate:metadata:labels:app: nginxspec:containers:- image: nginximagePullPolicy: Alwaysname: httpresources: {}terminationMessagePath: /dev/termination-logterminationMessagePolicy: Fileresources:limits:cpu: "500m"memory: "128Mi"livenessProbe:httpGet:path: /port: 80initialDelaySeconds: 15timeoutSeconds: 1readinessProbe:httpGet:path: /port: 80initialDelaySeconds: 5timeoutSeconds: 1