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

   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":true}}'

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.

Namespaces