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使用Deployment运行一个无状态应用

本文介绍通过Kubernetes Deployment对象如何去运行一个应用.

• 教程目标
• 准备开始
• 创建和探究一个nginx deployment
• 更新deployment
• 通过增加副本数来弹缩应用
• 删除deployment
• ReplicationControllers – 旧的方式
• 接下来

教程目标

• 创建一个nginx deployment.
• 使用kubectl列举关于deployment信息.
• 更新deployment.

准备开始

你必须拥有一个 Kubernetes 的集群，同时你的 Kubernetes 集群必须带有 kubectl 命令行工具。 如果你还没有集群，你可以通过 Minikube 构建一 个你自己的集群，或者你可以使用下面任意一个 Kubernetes 工具构建：

• Katacoda
• Play with Kubernetes

为了检查版本, 输入 kubectl version.

创建和探究一个nginx deployment

你可以通过创建一个Kubernetes Deployment对象来运行一个应用, 可以在一个YAML文件中描述Deployment. 例如, 下面这个YAML文件描述了一个运行nginx:1.7.9 Docker镜像的Deployment:

deployment.yaml docs/tasks/run-application

apiVersion: apps/v1beta1 kind: Deployment metadata: name: nginx-deployment spec: replicas: 2 # tells deployment to run 2 pods matching the template template: # create pods using pod definition in this template metadata: # unlike pod-nginx.yaml, the name is not included in the meta data as a unique name is # generated from the deployment name labels: app: nginx spec: containers: - name: nginx image: nginx:1.7.9 ports: - containerPort: 80

1. 通过YAML文件创建一个Deployment:

   kubectl create -f https://k8s.io/docs/tasks/run-application/deployment.yaml

2. 展示Deployment相关信息:

   kubectl describe deployment nginx-deployment

   user@computer:~/website$ kubectl describe deployment nginx-deployment
   Name:     nginx-deployment
   Namespace:    default
   CreationTimestamp:  Tue, 30 Aug 2016 18:11:37 -0700
   Labels:     app=nginx
   Annotations:    deployment.kubernetes.io/revision=1
   Selector:   app=nginx
   Replicas:   2 desired | 2 updated | 2 total | 2 available | 0 unavailable
   StrategyType:   RollingUpdate
   MinReadySeconds:  0
   RollingUpdateStrategy:  1 max unavailable, 1 max surge
   Pod Template:
     Labels:       app=nginx
     Containers:
      nginx:
       Image:              nginx:1.7.9
       Port:               80/TCP
       Environment:        <none>
       Mounts:             <none>
     Volumes:              <none>
   Conditions:
     Type          Status  Reason
     ----          ------  ------
     Available     True    MinimumReplicasAvailable
     Progressing   True    NewReplicaSetAvailable
   OldReplicaSets:   <none>
   NewReplicaSet:    nginx-deployment-1771418926 (2/2 replicas created)
   No events.
   

3. 列出deployment创建的pods:

   kubectl get pods -l app=nginx

   NAME                                READY     STATUS    RESTARTS   AGE
   nginx-deployment-1771418926-7o5ns   1/1       Running   0          16h
   nginx-deployment-1771418926-r18az   1/1       Running   0          16h
   

4. 展示某一个pod信息:

   kubectl describe pod

   该处 <pod-name> 指某一pod的名称.

更新deployment

你可以通过更新一个新的YAML文件来更新deployment. 下面的YAML文件指定该deployment镜像更新为nginx 1.8.

deployment-update.yaml docs/tasks/run-application
apiVersion: apps/v1beta1 kind: Deployment metadata: name: nginx-deployment spec: replicas: 2 template: metadata: labels: app: nginx spec: containers: - name: nginx image: nginx:1.8 # Update the version of nginx from 1.7.9 to 1.8 ports: - containerPort: 80

1. 应用新的YAML:

   kubectl apply -f https://k8s.io/docs/tutorials/stateless-application/deployment-update.yaml

2. 查看该deployment创建的pods以新的名称同时删除旧的pods:

   kubectl get pods -l app=nginx

通过增加副本数来弹缩应用

你可以通过应用新的YAML文件来增加Deployment中pods的数量. 该YAML文件将replicas设置为4, 指定该Deployment应有4个pods:

deployment-scale.yaml docs/tasks/run-application
apiVersion: apps/v1beta1 kind: Deployment metadata: name: nginx-deployment spec: replicas: 4 # Update the replicas from 2 to 4 template: metadata: labels: app: nginx spec: containers: - name: nginx image: nginx:1.8 ports: - containerPort: 80

1. 应用新的YAML文件:

   kubectl apply -f https://k8s.io/docs/tutorials/stateless-application/deployment-scale.yaml

2. 验证Deployment有4个pods:

   kubectl get pods -l app=nginx

   输出的结果类似于:

   NAME                               READY     STATUS    RESTARTS   AGE
   nginx-deployment-148880595-4zdqq   1/1       Running   0          25s
   nginx-deployment-148880595-6zgi1   1/1       Running   0          25s
   nginx-deployment-148880595-fxcez   1/1       Running   0          2m
   nginx-deployment-148880595-rwovn   1/1       Running   0          2m
   

删除deployment

通过名称删除deployment:

kubectl delete deployment nginx-deployment

ReplicationControllers – 旧的方式

创建一个多副本应用首选方法是使用Deployment,反过来使用ReplicaSet. 在Deployment和ReplicaSet加入到Kubernetes之前, 多副本应用通过ReplicationController来配置.

接下来

• 了解更多 Deployment objects.

反馈

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