CronJob
Previously we already create a Job to backup the postgres database service that we have. But its inconvenient to run this job manually every time we want to backup. We can use CronJob for this.
CronJob create a job on a repeating schedule. It runs a Job periodically on a given schedule, written in Cron format.
# * * * * * <command to execute>
# | | | | |
# | | | | day of the week (0–6) (Sunday to Saturday;
# | | | month (1–12) 7 is also Sunday on some systems)
# | | day of the month (1–31)
# | hour (0–23)
# minute (0–59)
I usually use this website (crontab.guru) to check if my cron format is correct and will behave as expected or not.
Create CronJob to Dump Database
Lets create a CronJob that will run a job we previously created to dump PostgreSQL database. The basic CronJob definition/configuration is simple.
apiVersion: batch/v1
kind: CronJob
metadata:
name: postgres-backup
spec:
schedule: "0 0 * * *" # Runs at midnight daily
jobTemplate:
We just need to define our CronJob above, specify the schedule (in here I use 0 0 * * * so it will run every midnight), and then put the job definition we previously created into the jobTemplate section.
Your full file should looks like this.
apiVersion: batch/v1
kind: CronJob
metadata:
name: postgres-backup
spec:
schedule: "0 0 * * *"
jobTemplate:
spec:
ttlSecondsAfterFinished: 60
template:
spec:
containers:
- name: pg-backup
image: postgres:17
command: ["/bin/sh", "-c"]
args:
- |
echo "Starting PostgreSQL backup..."
pg_dump -h postgres.default.svc.cluster.local -d mydb > /backup/postgres_backup_$(date +%Y%m%d%H%M%S).sql
echo "Backup completed!"
env:
- name: PGUSER
valueFrom:
secretKeyRef:
name: postgres-secret
key: POSTGRES_USER
- name: PGPASSWORD
valueFrom:
secretKeyRef:
name: postgres-secret
key: POSTGRES_PASSWORD
volumeMounts:
- mountPath: /backup
name: backup-storage
volumes:
- name: backup-storage
persistentVolumeClaim:
claimName: postgres-backup-pvc
restartPolicy: Never
Lets name the file as postgres-backup-cronjob.yaml then apply the file.
➜ kubectl apply -f postgres-backup-cronjob.yaml
cronjob.batch/postgres-backup created
Validate that your CronJob is properly created.
➜ kubectl get cronjob
NAME SCHEDULE TIMEZONE SUSPEND ACTIVE LAST SCHEDULE AGE
postgres-backup 0 0 * * * <none> False 0 <none> 3s
As you can see above we now have a CronJob that will create a Job every midnight to run pg_dump. We also can explicitly specify a timezone or if we left it empty it will be defaulted to local timezone.
For CronJobs with no time zone specified, the kube-controller-manager interprets schedules relative to its local time zone.
Manually Trigger Job
Waiting the job to run at midnight is not ideal when we want to test if our CronJob will run properly or not. In this case we can manually trigger the scheduled job using this command below.
➜ kubectl create job --from=cronjob/postgres-backup backup-manual
job.batch/backup-manual created
Lets get list of the job and you should see the manually triggered job. Like before, we can get the job logs to make sure that it run successfully.
➜ kkubectl get jobs
NAME STATUS COMPLETIONS DURATION AGE
backup-manual Complete 1/1 4s 5s
➜ kkubectl logs jobs/backup-manual
Starting PostgreSQL backup...
Backup completed!