从零开始Kubernetes CronJob实现任务调度

获取最新版本

curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"

指定版本

curl -LO https://dl.k8s.io/release/v1.23.0/bin/linux/amd64/kubectl

[root@ydt local]# curl -LO "https://dl.k8s.io/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl.sha256"
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   154  100   154    0     0    152      0  0:00:01  0:00:01 --:--:--   152
100    64  100    64    0     0     33      0  0:00:01  0:00:01 --:--:--    75
[root@ydt local]# echo "$(cat kubectl.sha256)  kubectl" | sha256sum --check
kubectl: 确定

一般来说要么指定版本，要么取最新的版本校验文档，都不会有问题

[root@ydt local]# sudo install -o root -g root -m 0755 kubectl /usr/local/bin/kubectl
[root@ydt local]# kubectl version --client --output=yaml
clientVersion:
  buildDate: "2022-04-14T08:49:13Z"
  compiler: gc
  gitCommit: ad3338546da947756e8a88aa6822e9c11e7eac22
  gitTreeState: clean
  gitVersion: v1.23.6
  goVersion: go1.17.9
  major: "1"
  minor: "23"
  platform: linux/amd64

Minikube是一个快速搭建单节点Kubenetes集群的工具，它对硬件资源没有太高的要求，方便开发人员学习使用，或者进行日常的开发。

#安装须知：
2 CPUs or more
2GB of free memory
20GB of free disk space
Internet connection
Container or virtual machine manager, such as: Docker, Hyperkit, Hyper-V, KVM, Parallels, Podman, VirtualBox, or VMware Fusion/Workstation #一般都是Docker容器

#安装命令
curl -LO https://storage.googleapis.com/minikube/releases/latest/minikube-latest.x86_64.rpm

sudo rpm -Uvh minikube-latest.x86_64.rpm

#启动Docker
service docker start

# 创建用户，如果你使用的是root用户的话会无法启动并提示如下信息，那是因为Minikube不允许使用root权限启动，需要创建一个非root账号再启动
useradd -u 1024 -g docker macro
# 设置用户密码，这个密码需要复杂点，比如aaa@123
passwd macro  
# 切换用户
su macro

#启动集群
minikube start --driver=docker

#遇到的报错：
#1、Sorry, Kubernetes 1.23.3 requires conntrack to be installed in root’s path
#安装conntrack解决,安装不了换个yum源，比如阿里云
yum install conntrack

#2、/proc/sys/net/bridge/bridge-nf-call-iptables contents are not set to 1
#执行：echo "1" >/proc/sys/net/bridge/bridge-nf-call-iptables

#3、/proc/sys/net/ipv4/ip_forward contents are not set to 1
#执行：echo 1 > /proc/sys/net/ipv4/ip_forward

#4、hostname "***" could not be reached
#将 127.0.0.1 映射本机的hostname

#看到如下启动结果，表示启动成功
[macro@ydt local]$ minikube start --driver=docker
* Centos 7.7.1908 上的 minikube v1.25.2
* 根据现有的配置文件使用 docker 驱动程序
* Starting control plane node minikube in cluster minikube
* Pulling base image ...
* Updating the running docker "minikube" container ...
! This container is having trouble accessing https://k8s.gcr.io
* To pull new external images, you may need to configure a proxy: https://minikube.sigs.k8s.io/docs/reference/networking/proxy/
* 正在 Docker 20.10.12 中准备 Kubernetes v1.23.3…
  - kubelet.housekeeping-interval=5m
* Verifying Kubernetes components...
  - Using image gcr.io/k8s-minikube/storage-provisioner:v5
* Enabled addons: storage-provisioner, default-storageclass
* Done! kubectl is now configured to use "minikube" cluster and "default" namespace by default

#查看集群节点（单节点集群）
[macro@ydt local]$ kubectl get nodes
NAME       STATUS   ROLES                  AGE   VERSION
minikube   Ready    control-plane,master   90m   v1.23.3

这里先来一个demo，一分钟打印一句话：hello cron-job

apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: cronjob-test
spec:
  schedule: "*/1 * * * *" #表明每一分钟都会执行这个任务
  jobTemplate: #job控制器模板，用于为cronjob控制器生成job对象，下面其实就是job的定义
    spec:
      template: #模板，当副本数量不足时，会根据下面的模板创建pod副本
        spec:
          containers:
          - name: busybox-container
            image: busybox
            args:
            - /bin/sh
            - -c
            - date; echo "hello cron-job"
          restartPolicy: OnFailure #重启策略只能设置为Never或者OnFailure

[macro@ydt local]$ kubectl create -f cronjob.yaml
Warning: batch/v1beta1 CronJob is deprecated in v1.21+, unavailable in v1.25+; use batch/v1 CronJob
cronjob.batch/cronjob-test created

[macro@ydt local]$ kubectl  get pods
NAME                          READY   STATUS      RESTARTS   AGE
cronjob-test-27516061-k4vwv   0/1     Completed   0          2m10s
cronjob-test-27516062-xlpbj   0/1     Completed   0          70s
cronjob-test-27516063-n9pc9   0/1     Completed   0          10s
[macro@ydt local]$ kubectl logs cronjob-test-27516061-k4vwv
Tue Apr 26 09:01:06 UTC 2022
hello cron-job

[macro@ydt root]$ kubectl get cj -n default -w
NAME           SCHEDULE      SUSPEND   ACTIVE   LAST SCHEDULE   AGE
cronjob-test   */1 * * * *   False     0        52s             2m34s
cronjob-test   */1 * * * *   False     1        0s              2m42s
cronjob-test   */1 * * * *   False     0        10s             2m52s
cronjob-test   */1 * * * *   False     0        10s             2m52s
cronjob-test   */1 * * * *   False     1        0s              3m42s
cronjob-test   */1 * * * *   False     0        9s              3m51s
cronjob-test   */1 * * * *   False     0        9s              3m51s
cronjob-test   */1 * * * *   False     1        0s              4m42s
cronjob-test   */1 * * * *   False     0        8s              4m50s
cronjob-test   */1 * * * *   False     0        8s              4m50s

发现每隔一分钟，cronjob就会生成一个pod容器执行job

如果pod建立失败，可以查看具体原因：

kubectl describe pod cronjob-test-27517357-qfznq

[macro@ydt local]$ kubectl delete cronjob cronjob-test
cronjob.batch "cronjob-test" deleted

#开启插件
[macro@ydt local]$ minikube addons enable dashboard
  - Using image kubernetesui/dashboard:v2.3.1
  - Using image kubernetesui/metrics-scraper:v1.0.7
* Some dashboard features require the metrics-server addon. To enable all features please run:

        minikube addons enable metrics-server


* 启动 'dashboard' 插件

#暴露外部访问ip
[macro@ydt local]$ kubectl proxy --port=8100 --address=192.168.137.128 --accept-hosts='^.*' &
[1] 343326
[macro@ydt local]$ Starting to serve on 192.168.137.128:8100

#获取访问路径
[macro@ydt local]$ minikube dashboard --url
* 正在验证 dashboard 运行情况 ...
* Launching proxy ...
* 正在验证 proxy 运行状况 ...
http://127.0.0.1:36290/api/v1/namespaces/kubernetes-dashboard/services/http:kubernetes-dashboard:/proxy/

注意，每次minikube单节点集群重启后都需要重新执行，得到新的访问路径！

可以通过Shell脚本执行远程服务接口

apiVersion: batch/v1beta1
kind: CronJob
metadata:
  namespace: kube-system  #不要跟服务同一个namespace,否则successfulJobsHistoryLimit,failedJobsHistoryLimit不生效
  name: cronjob-test
spec:
  schedule: "0 0/1 * * *"
  jobTemplate:
    spec:
      template:
        spec:
          containers:
          - name: busybox-container
            image: busybox
            command:
              - wget
              - "http://服务名.服务所在namespace/infoVisitLog" 
          restartPolicy: OnFailure
  successfulJobsHistoryLimit: 2
  failedJobsHistoryLimit: 2