Run RethinkDB in a docker containter. Data are stored in /data, a volume expected to be linked to a host directory.
If an environment variable BACKUP_INTERVAL is set, this container will periodically dump the database to a gzip file located in /backup, which again is expected to be linked to the host. The value of BACKUP_INTERVAL follows the format of bash sleep command, i.e. the default unit is second, m for minutes, h for hours and d for days. For example, set BACKUP_INTERVAL=1h will backup the database every hour.