When CI service is activated in a project, here is the kind of log we can found in access_log at each report access:
GET /sparklines.php?sparklines%5B%5D=http%3A%2F%2Ftuleap_web_1.tuleap-aio-dev.docker%2Fplugins%2Ftracker%2F%3Faid%3D53&sparklines%5B%5D=http%3A%2F%2Ftuleap_web_1.tuleap-aio-dev.docker%2Fgoto%3Fkey%3Dbuild%26val%3D36%26group_id%3D102&sparklines%5B%5D=http%3A%2F%2Ftuleap_web_1.tuleap-aio-dev.docker%2Fplugins%2Ftracker%2F%3Faid%3D13 HTTP/1.1"
The more artifacts are displayed in the reports, longer the previous line is.