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How to use Kubernetes Job Resource Objects? I believe that most people do not know how to use Job resource objects. In order to let everyone learn, I summarized the following contents for everyone. Without saying much, let's look down together.

concept

In some scenarios, it is desirable to run containers to perform a specific task, and once the task is completed, the container is no longer necessary. In this scenario, the creation of a pod seems inappropriate. Job is a one-time job. Run a container through Job, and when its task is finished, it automatically exits, and the cluster does not wake it up again.

From the running mode of the program, Pods can be divided into two categories: long-running services (jboss, mysql, etc.) and one-time tasks (data calculation, testing). Pods created by RC are long-running services. Job is mostly used to execute one-time tasks, batch work, etc., and will stop after execution (status.phase becomes Succeeded).

Environment Description Host IP Address Service master192.168.1.21k8snode01192.168.1.22k8snode02192.168.1.23k8s

The experiment based on [ https://blog.51cto.com/14320361/2464655]() continues

Kubernetes supports the following types of non-parallel jobs: Usually a pod is created until it ends successfully. Job with fixed number of finishes: Set spec.completions, create multiple pods until.spec.completions pods successfully finish. Parallel jobs with work queues: Set.spec.Parallelism but not.spec.completions, and a job is considered successful when all pods are complete and at least one succeeds. Job Controller

The Job Controller is responsible for creating a pod based on Job Spec and continuously monitoring the status of the pod until it ends successfully, if it fails, deciding whether to create a new pod and retry the task again according to the restart Policy (only OnFailure and Never are supported, not Always).

Example (1) Write a job yaml file [root@master yaml]# vim jop.yamlkind: JobapiVersion: batch/v1metadata: name: test-jobspec: template: metadata: name: test-job spec: containers: - name: hello image: busybox command: ["echo","hello k8s job! "] restartPolicy: Never (2) Execute [root@master yaml]# kubectl apply -f jop.yaml (3) View [root@master yaml]# kubectl get pod

View logs [root@master yaml]# kubectl logs test-job-gs45w

We can see that job is different from other resource objects. It only executes one-time tasks. By default, job ends after pod runs overnight, and the status is Completed.

(4) Modify the yaml file of jop, replace the echo command with garbled [root@master yaml]# vim jop.yamlkind: JobapiVersion: batch/v1metadata: name: test-jobspec: template: metadata: name: test-job spec: containers: - name: hello image: busybox command: ["asdasxsddwefew","hello k8s job! "] #Modify restartPolicy: Never (5) delete the previous pod[root@master yaml]# kubectl delete jobs.batch test-job (6) execute [root@master yaml]# kubectl apply -f hop.yaml (7) check [root@master yaml]# kubectl get pod -w

It creates pods until the command is complete.

(8) Modify the yaml file of jop, modify the restart policy [root@master yaml]# vim jop.yaml kind: JobapiVersion: batch/v1metadata: name: test-jobspec: template: metadata: name: test-job spec: containers: - name: hello image: busybox command: ["asdasxsddwefew","hello k8s job! "] restartPolicy: OnFailure (9) Delete previous pod[root@master yaml]# kubectl delete jobs.batch test-job (10) Execute [root@master yaml]# kubectl apply -f hop.yaml (11) Check [root@master yaml]# kubectl get pod -w

It will restart the pod to complete the command until it restarts a certain number of times and deletes the job.

Second, improve the efficiency of Job execution 1. We can add the [parallelism]() option to the Job.spec field. Indicates how many pods are running simultaneously to perform tasks. (1) Write a job yaml file [root@master yaml]# vim jop.yamlkind: JobapiVersion: batch/v1metadata: name: test-jobspec: parallelism: 2 #Enable several pod templates simultaneously: metadata: name: test-job spec: containers: - name: hello image: busybox command: ["echo","hello k8s job! "] restart Policy: OnFailure (3) Execute [root@master yaml]# kubectl apply -f jop.yaml (4) Check [root@master yaml]# kubectl get pod

view the log

2. We can add the complements option to the Job.spec field. yaml file [root@master yaml]# vim jop.yamlkind: JobapiVersion: batch/v1metadata: name: test-jobspec: complements: 8 #Total number of running pods 8 parallelism: 2 #Run two pod templates simultaneously: metadata: name: test-job spec: containers: - name: hello image: busybox command: ["echo","hello k8s job! "] restartPolicy: OnFailure

Job field explanation:

completions: number of Pods needed to run successfully to mark the end of the Job, default is 1

parallelism: indicates the number of Pods running in parallel, default is 1

activeDeadlineSeconds: The maximum retry time for a failed flag pod, beyond which retries will not continue.

(2) Delete the previous pod[root@master yaml]# kubectl delete jobs.batch test-job (3) Execute [root@master yaml]# kubectl apply -f hop.yaml (4) Check [root@master yaml]# kubectl get pod

You can see that the pods are activated by two.

3. How to execute Job (1) on time Write a cronjob yaml file [root@master yaml]# vim cronjop.yamlkind: CronJobapiVersion: batch/v1beta1metadata: name: hellospec: schedule: "*/1 * **" #limited time jobTemplate: spec: template: spec: containers: - name: hello image: busybox command: ["echo","hello","cronjob"] restartPolicy: OnFailure (2) Delete the previous pod[root@master yaml]# kubectl delete jobs.batch test-job (3) Execute [root@master yaml]# kubectl apply -f hop.yaml (4) Check [root@master yaml]# kubectl get pod

[root@master yaml]# kubectl get cronjobs.batch

Looking at the status of the Pod, you will find that a new Pod is running every minute to execute any command specified.

Business.

Exercise: Run the crontab task above in 2020.1.15.10.5 minutes. (1) Write a cronjob yaml file [root@master yaml]# vim cronjop.yamlkind: CronJobapiVersion: batch/v1beta1metadata: name: hellospec: schedule: "5 10 15 1 *" #limited time jobTemplate: spec: template: spec: containers: - name: hello image: busybox command: ["echo","hello","cronjob"] restartPolicy: OnFailure (2) Delete pod[root@master yaml]# kubectl delete cronjobs.batch hello (3) Execute [root@master yaml]# kubectl apply -f hop.yaml (4) Check [root@master yaml]# kubectl get pod

At this point, it may be found that if a specific time is specified, the task may not be carried out.

(5) Add apiVersion library [root@master yaml]# vim /etc/kubernetes/manifests/kube-apiserver.yaml spec: containers: - command: - kube-apiserver - --runtime-config=batch/v2alpha1=true #Add

(6) Restart kubelet[root@master yaml]# systemctl restart kubelet.service (7) Check api versions [root@master yaml]# kubectl api-versions

(8) Write a cronjob yaml file [root@master yaml]# vim cronjop.yamlkind: CronJobapiVersion: batch/v1beta1metadata: name: hellospec: schedule: "47 10 15 1 *" #limited time jobTemplate: spec: template: spec: containers: - name: hello image: busybox command: ["echo","hello","cronjob"] restart Policy: OnFailure (9) Execute [root@master yaml]# kubectl apply -f jop.yaml (4) Check [root@master yaml]# kubectl get pod -w

Note: At this time, the Job for the specified time still cannot run normally, because K8s official has not perfected this function in the support of cronjob this resource object, and it has yet to be developed.

Just like Job resources, concurrent Job parameters are also supported under cronjob.spec.jobTemplate.spec:

parallelism, also supports the total number of completed pods parameter: completionsr

The above is how to use Kubernetes Job resource object. Is there any harvest after reading it? If you want to know more about it, welcome to pay attention to industry information!

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