ubuntu-repository-cache fails to sync because its logs file does not exist

[Junien F]

Hi,

We redeployed some environments with the latest ubuntu-repository-cache today, and noticed that the cron job fails to start because the log file does not exist.

The cron job is :

ubuntu@machine-1:~$ cat /etc/cron.d/ubuntu-repository-cache_rsync
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
LOCAL_UNIT=ubuntu-repository-cache/1
APACHE_ROOT=/srv/ubuntu-repository-cache/ephemeral/0/apache
SYNC_HOST=archive.ubuntu.com
UNIT_PATH=unit-ubuntu-repository-cache-1
# This cronjob will make the leader sync its view of the metadata with upstream
# It will then trigger a juju-run to let its peers synchronise.
59 * * * * www-sync python3 /var/lib/juju/agents/unit-ubuntu-repository-cache-1/charm/lib/ubuntu_repository_cache/metadata_sync.py >> /var/log/repository-sync-cron.log

and the /var/log/repository-sync-cron.log doesn't exist. For now, I created it manually on all impacted units and chowned it to www-sync, but a proper fix needs to be implemented.

We should probably :
 * create a dedicated directory in /var/log, with the proper permissions, and log there
 * timestamp the logs
 * rotate them

The last 2 items can be handled by e.g. Python logging using https://docs.python.org/3/library/logging.handlers.html#timedrotatingfilehandler