deployment运行demo代码

Deployment是kubernetes中最常用的资源对象，为ReplicaSet和Pod的创建提供了一种声明式的定义方法，在Deployment对象中描述一个期望的状态，Deployment控制器就会按照一定的控制速率把实际状态改成期望状态，通过定义一个Deployment控制器会创建一个新的ReplicaSet控制器，通过ReplicaSet创建pod，删除Deployment控制器，也会删除Deployment控制器下对应的ReplicaSet控制器和pod资源.

使用Deployment而不直接创建ReplicaSet是因为Deployment对象拥有许多ReplicaSet没有的特性，例如滚动升级、金丝雀发布、蓝绿部署和回滚。

扩展：声明式定义是指直接修改资源清单yaml文件，然后通过kubectl apply -f 资源清单yaml文件，就可以更改资源。

apiVersion: apps/v1kind: Deploymentmetadata: name: myapp-v1spec: replicas: 3 selector: matchLabels: app: myapp version: v1 template: metadata: labels: app: myapp version: v1 spec: containers: - name: myapp image: janakiramm/myapp:v2 imagePullPolicy: IfNotPresent ports: - containerPort: 80 version: v1 template: metadata: labels: app: myapp version: v1 spec: containers: - name: myapp image: janakiramm/myapp:v2 imagePullPolicy: IfNotPresent ports: - containerPort: 80 startupProbe: periodSeconds: 5 initialDelaySeconds: 20 timeoutSeconds: 10 httpGet: scheme: HTTP port: 80 path: / livenessProbe: periodSeconds: 5 initialDelaySeconds: 20 timeoutSeconds: 10 httpGet: scheme: HTTP port: 80 path: / readinessProbe: periodSeconds: 5 initialDelaySeconds: 20 timeoutSeconds: 10 httpGet: scheme: HTTP port: 80 path: /