Ansible cronjob - adding a timestamp to filename - cron

Question

I am trying to write an Ansible task that does a daily backup of our database and timestamps the name of the file.
- name: Run cronjob to backup database.
become_user: postgres
cron:
name: "Export database"
special_time: daily
job: pg_dump -U db_user -W -F t db_name > filename.tar
I tried simply appending $(date +%Y-%m-%d-%H.%M.%S) to filename.tar e.g
filename-$(date +%Y-%m-%d-%H.%M.%S).tar
However this wont work as the value of the date is set only once when the task is ran, leading to every filename having a timestamp of when the ansible task was ran.
I'm looking for around this, and to allow this job to generate a new timestamp for each filename.

Answer 1

In general, we have a practice of creating shell scripts to handle database backups. This allows us to capture exit code(s), and log/send alerts accordingly.
Though a simple one with just one pg_dump command will do, something similar as below should be possible:
Example:
db-backup.sh
#!/bin/bash
DB_USER="dbuser"
DB_PASSWORD="dbpassword"
DB_NAME="db_name"
BACKUP_FILE="db-backup-$(date +%Y-%m-%d-%H.%M.%S).tar"
cmd="pg_dump -U ${DB_USER} -W -F t ${DB_NAME} > ${BACKUP_FILE}"
if $cmd; then
# do something
else
# do something else
fi
Then in Ansible, copy this script to target, and create cron job to run this script.
# Copying to temp directory for example
- name: copy database backup script
copy:
src: 'db-backup.sh'
dest: '/tmp/db-backup.sh'
mode: '0755'
owner: 'postgres'
group: 'postgres'
- name: run cronjob to backup database
become_user: postgres
cron:
name: 'Export database'
special_time: 'daily'
job: '/tmp/db-backup.sh'