kubernetes-Jobs

  A Job creates one or more Pods and ensures that a specified number of them successfully terminate. As pods successfully complete, the Job tracks the successful completions. When a specified number of successful completions is reached, the task (ie, Job) is complete. Deleting a Job will clean up the Pods it created.

A simple case is to create one Job object in order to reliably run one Pod to completion. The Job object will start a new Pod if the first Pod fails or is deleted (for example due to a node hardware failure or a node reboot).

You can also use a Job to run multiple Pods in parallel.

LAB

1. Job manifest file: 


apiVersion: batch/v1
kind: Job
metadata:
  name: countdown
spec:
  template:
    metadata:
      name: countdown
    spec:
      containers:
      - name: counter
        image: centos:7
        command:
         - "bin/bash"
         - "-c"
         - "for i in 9 8 7 6 5 4 3 2 1 ; do echo $i ; done"
      restartPolicy: Never



*************************************************************************************************************************************************

2. Create & Display


kubectl create -f countdown-jobs.yaml

kubectl get jobs

kubectl get po

kubectl describe jobs countdown



*************************************************************************************************************************************************

3. Test


kubectl logs [POD_NAME] 



*************************************************************************************************************************************************

4. Cleanup


kubectl delete jobs countdown

kubectl get po



*************************************************************************************************************************************************

**************Cron Job***********************

#cronjob.yaml
apiVersion: batch/v1beta1
kind: CronJob
metadata:
   name: cronjob
spec:
   schedule: "* * * * *"
   successfulJobsHistoryLimit: 2
   failedJobsHistoryLimit: 1
   suspend: true
   jobTemplate:
     spec:
       template:
         spec:
           containers:
           - name: busybox
             image: busybox
             command: ["echo", "Hello world"]
           restartPolicy: Never


kubectl create -f cronjob.yaml


kubectl patch cronjob cronjob -p '{"spec":{"suspend":false}}'


concurrencyPolicy:   Allow,Forbid,Replace

Allow to allow multiple jobs runs at a time

Forbid to wait a running job to finish first and then execute another instance of the job

Replace to replace an existing job.

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