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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

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：

To check the version, enter 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

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