Since `supervisord` [lacks an option for compression of rotated log files](https://github.com/Supervisor/supervisor/issues/322), I wrote this script. It works well to live in `/etc/cron.daily`.

supervisor-log-compress.sh

#!/usr/bin/env bash
  
# supervisor-log-compress.sh
#
# supervisord writes logs, and rotates them, but does not compress old log
# files. This script is meant to help with that cleanup, reclaiming storage.
#
# A nice place for this script is in: /etc/cron.daily/

for f in /var/log/supervisor/*.log.*; do
  if [ ! "${f##*.}" == 'gz' ]; then # Exclude already compressed files
    gzip "${f}"
  fi
done