Kubernetes概念之deployment

一整天一整天的坐在办公室，真的很~~~，懵圈中....，求解救。

本文通过《Kubernetes权威指南》的概念部分学习总结 

Deployment作用

Deployment与RC的作用其实是一样的，都是为了管理Pod的副本数

 

Deployment的使用场景

1）创建一个Deployment对象来生成对应的Replica Set并完成Pod副本的创建过程。

2）检查Deployment的状态来看部署动作是否完成（Pod副本的数量是否达到了预期的值）

3）更新Deployment以创建新的Pod

4）如果当前Deployment不稳定，则回滚到一个早先的Deployment版本

5）挂起或者恢复一个Deployment

 

例子

创建一个deployment，管理一个运行tomcat的pod

 

1、创建deployment.yaml文件

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: frontend
spec:
  replicas: 1
  selector:
    matchLabels:
      tier: frontend
    matchExpressions:
      - {key: tier, operator: In, values: [frontend]}

  template:
    metadata:
      labels:
        app: app-demo
        tier: frontend
    spec:
      containers:
      - name: tomcat-demo
        image: tomcat
        imagePullPolicy: IfNotPresent
        ports:
        - containerPort: 8080 

2、创建deployment

[root@master ~]# kubectl create -f tomcat-deployment.yaml 
deployment.extensions/frontend created

3、查看deployment信息

[root@master ~]# kubectl get deployment
NAME       DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
frontend   1         1         1            1           23s

输出结果的含义：

DESIRED：Pod副本数量的期望值，即deployment里定义的Replica

CURRENT：当前Replica的值，这个值会不断的增加，直到达到DESIRED为止，表明整个部署过程完成

UP-TO-DATE：最新版本的Pod的副本数量，用于指示在滚动升级过程中，有多少个Pod副本已经成功升级

AVAILABEL：当前集群中可用的Pod副本数量，即集群中当前存活的Pod数量

 

4、查看Pods信息

[root@master ~]# kubectl get pods
NAME                        READY     STATUS    RESTARTS   AGE
frontend-6cfdb4d686-j8jj7   1/1       Running   0          9m

5、查看deployment的详细信息

[root@master ~]# kubectl describe deployment
Name:                   frontend
Namespace:              default
CreationTimestamp:      Fri, 20 Sep 2019 06:40:40 +0000
Labels:                 app=app-demo
                        tier=frontend
Annotations:            deployment.kubernetes.io/revision=1
Selector:               tier=frontend,tier in (frontend)
Replicas:               1 desired | 1 updated | 1 total | 1 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  1 max unavailable, 1 max surge
Pod Template:
  Labels:  app=app-demo
           tier=frontend
  Containers:
   tomcat-demo:
    Image:        tomcat
    Port:         8080/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
  Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  <none>
NewReplicaSet:   frontend-6cfdb4d686 (1/1 replicas created)
Events:
  Type    Reason             Age   From                   Message
  ----    ------             ----  ----                   -------
  Normal  ScalingReplicaSet  9m    deployment-controller  Scaled up replica set frontend-6cfdb4d686 to 1