Kubernetes 应用程序(一) 使用Deployment运行应用程序

这个章节展示了如何使用Kubernetes Deployment对象运行一个应用程序。

创建一个nginx deployment

可以用Kubernetes Deployment对象创建一个应用程序，并且可以用YAML文件来描述Deployment。下面这个YAML文件描述了一个Deployment运行了一个nginx:1.7.9镜像。

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.基于YAML文件创建一个Deployment:

kubectl create -f nginx.yaml

2.显示这个Deployment详细信息：

kubectl describe deployment nginx-deployment

 user@computer:~/kubernetes.github.io$ kubectl describe deployment nginx-deployment
 Name:     nginx-deployment
 Namespace:    default
 CreationTimestamp:  Tue, 30 Aug 2016 18:11:37 -0700
 Labels:     app=nginx
 Selector:   app=nginx
 Replicas:   2 updated | 2 total | 2 available | 0 unavailable
 StrategyType:   RollingUpdate
 MinReadySeconds:  0
 RollingUpdateStrategy:  1 max unavailable, 1 max surge
 Conditions:
   Type          Status  Reason
   ----          ------  ------
   Available     True    MinimumReplicasAvailable
 OldReplicaSets:   <none>
 NewReplicaSet:    nginx-deployment-1771418926 (2/2 replicas created)
 No events.

3.查看创建的deployment列表：

 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.显示pod的详细信息：

kubectl describe pod <pod-name>

更新deployment

可以用一个新的YAML文件更新deployment。这个YAML文件指定了deployment把镜像更新成nginx 1.8。

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.更新deployment

kubectl apply -f nginx.yaml

2.观察这个deployment创建了一个新的pod并且把老的删除：

kubectl get pods -l app=nginx

扩缩应用程序副本数量

可以使用一个新的YAML文件增加deployment里面pod的数量。这个YAML文件设置replicas为4，指定的Deployment将有4个pod:

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 nginx.yaml

2.验证这个Deployment是否包含4个pod:

kubectl get pods -l app=nginx

输出类似于下面：

 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

根据名字删除deployment:

kubectl delete deployment nginx-deployment

ReplicationControllers-上一代方法

创建包含多个副本的应用程序优先使用Deployment,反过来又使用ReplicaSet。在Deployment和ReplicaSet添加到Kubernetes里面之前是使用ReplicationController创建应用。