Today, only the db parameter is allowed to have default.
That was implemented, because of backwards compatibility with the former generate.py.
But it can easily be extended to all other config parameters, so that a config like this:
daily_report: type: script starts: 2018-01-01 granularity: days explode_by: wiki: wikis.txt weekly_report: type: script starts: 2018-01-01 granularity: weeks explode_by: wiki: wikis.txt monthly_report: type: script starts: 2018-01-01 granularity: months explode_by: wiki: wikis.txt
could look like that:
defaults: type: script starts: 2018-01-01 explode_by: wiki: wikis.txt daily_report: granularity: days weekly_report: granularity: weeks monthly_report: granularity: months
ReportUpdater documentation: https://wikitech.wikimedia.org/wiki/Analytics/Systems/Reportupdater
ReportUpdater source code: https://gerrit.wikimedia.org/r/#/admin/projects/analytics/reportupdater