I have a production magento 1.7 website. After migrated from a old server to a new one, from unknown reason the "Online Customers" under "Customers" didn't show any Online customers when there are actually many customer visit the site. I tried to google this problem but found nothing. The only change, from the old server to the new server, is the DB server switched from mysql 5.5 to MariaDB 10. Anything i can do to fix this?