Kubernetes基础：Deployments从beta版本到v1的变化对应方法

Deployments是在Kubernetes 1.2版本增加的特性，作为对于pod的控制，Deployments实现了声明式的应用发布和升级，保证了应用的高可用性和快速回滚的能力。在Kubernetes 1.8时相关API移至apps/v1beta2，在Kubernetes 1.9中整合至apps/v1，随着环境中的Kubernetes的升级，原有API的废弃导致Deployment的相应yaml文件需要修改，这篇文章以旧版的Prometheus的Deployment的修改为例，介绍Deployments修改需要注意的事项。

事前准备

本文示例中准备了Kubernetes 1.17的环境，环境的准备方法可参考如下Easyapck下的Ansible一键脚本。

• 单机版本或者集群版本环境搭建

[root@host131 ansible]# kubectl version
Client Version: version.Info{Major:"1", Minor:"17", GitVersion:"v1.17.0", GitCommit:"70132b0f130acc0bed193d9ba59dd186f0e634cf", GitTreeState:"clean", BuildDate:"2019-12-07T21:20:10Z", GoVersion:"go1.13.4", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"17", GitVersion:"v1.17.0", GitCommit:"70132b0f130acc0bed193d9ba59dd186f0e634cf", GitTreeState:"clean", BuildDate:"2019-12-07T21:12:17Z", GoVersion:"go1.13.4", Compiler:"gc", Platform:"linux/amd64"}
[root@host131 ansible]# 
[root@host131 ansible]# kubectl get nodes -o wide
NAME              STATUS   ROLES    AGE   VERSION   INTERNAL-IP       EXTERNAL-IP   OS-IMAGE                KERNEL-VERSION          CONTAINER-RUNTIME
192.168.163.131   Ready       18m   v1.17.0   192.168.163.131           CentOS Linux 7 (Core)   3.10.0-957.el7.x86_64   docker://18.9.7
[root@host131 ansible]#

Deployment示例准备

如下是Deployment在beta1阶段的Yaml文件示例

[root@host131 prometheus]# cat prometheus-deployment.yaml 
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: prometheus-deployment
  namespace: monitoring
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: prometheus-server
    spec:
      containers:
        - name: prometheus
          image: prom/prometheus:v2.12.0
          args:
            - "--config.file=/etc/prometheus/prometheus.yml"
            - "--storage.tsdb.path=/prometheus/"
          ports:
            - containerPort: 9090
          volumeMounts:
            - name: prometheus-config-volume
              mountPath: /etc/prometheus/
            - name: prometheus-storage-volume
              mountPath: /prometheus/
      volumes:
        - name: prometheus-config-volume
          configMap:
            defaultMode: 420
            name: prometheus-server-conf
  
        - name: prometheus-storage-volume
          emptyDir: {}
[root@host131 prometheus]# 

Yaml文件中所需要的命名空间ConfigMap等其他准备也事前已经准备：

[root@host131 prometheus]# kubectl get ns |grep monitoring
monitoring        Active   3m18s
[root@host131 prometheus]# kubectl get clusterrole |grep prometheus
prometheus                                                             3m1s
[root@host131 prometheus]# kubectl get clusterrolebindings |grep prometheus
prometheus                                             3m7s
[root@host131 prometheus]# kubectl get cm -n monitoring
NAME                     DATA   AGE
prometheus-server-conf   2      93s
[root@host131 prometheus]# 

API变化所需要的对应事项

从上述extensions/v1beta1到apps/v1，Deployment需要进行如下修改：

对应事项1: 修改apiVersion

在Kubernetes 1.17下直接使用使用上述Yaml文件进行Deployment的创建，首先会提示如下错误信息：

[root@host131 prometheus]# kubectl create -f prometheus-deployment.yaml 
error: unable to recognize "prometheus-deployment.yaml": no matches for kind "Deployment" in version "extensions/v1beta1"
[root@host131 prometheus]#

原因很简单，在这个版本中，extensions/v1beta1中已经没有Deployment了，已经被移除了，只能使用apps/v1了，然后做如下修改

[root@host131 prometheus]# cp prometheus-deployment.yaml prometheus-deployment.yaml.org
[root@host131 prometheus]# vi prometheus-deployment.yaml
[root@host131 prometheus]# diff prometheus-deployment.yaml prometheus-deployment.yaml.org 
1c1
< apiVersion: apps/v1
---
> apiVersion: extensions/v1beta1
[root@host131 prometheus]#

对应事项2: Deployment.spec中添加selector

修改apiVersion之后，再次执行kubectl create命令进行Deployment的创建，会得到如下错误信息提示：

[root@host131 prometheus]# kubectl create -f prometheus-deployment.yaml 
error: error validating "prometheus-deployment.yaml": error validating data: ValidationError(Deployment.spec): missing required field "selector" in io.k8s.api.apps.v1.DeploymentSpec; if you choose to ignore these errors, turn validation off with --validate=false
[root@host131 prometheus]#

原因也非常清晰，Deployment.spec中需要添加selector选择器，使用Kubernetes自带的帮助文档进行确认Deployment.spec.selector的写法

[root@host131 prometheus]# kubectl explain Deployment.spec.selector
KIND:     Deployment
VERSION:  apps/v1

RESOURCE: selector