Reported on http://lists.cendio.se/pipermail/thinlinc-technical/2015-March/000753.html . As Patrik Pira describes it: "this is due to anacrontab running cron.daily with "nice". cron.daily runs logrotate which upon rotating logfiles does a condrestart on vsm{agent|server} while running with the default niceness of 10."
This problem also affects tlwebadm and tlwebaccess. For the latter, tlstunnel is also runnnig with lower priority, which could lead to reduced performance.
Start by seeing if we can implement reopening the log files on SIGHUP. Then we can look further into the problem.
I can reproduce this issue on RHEL 6 by using default 'nice' value and forcing logrotate. This works well on RHEL 7. As of changes in r34910 ThinLinc does no longer support systems like RHEL6 which don't use systemd. However this should not be a big issue among users nowdays as most use newer dists. The changes in r34910 indirectly fixes this bug because systemd seems to not have any issues with unwanted renice. Will not mention this in release notes due to the nature of the fix.
Was also able to reproduce this on rhel6 and verified that it works on rhel8.