When CVS polling is enabled, the "high watermark" timestamp that cvs polls on for changes does not update until a build finishes. This causes multiple builds to trigger on the same changes.
For example, a build that take 7 mins, set to poll every 5, produces the following output on its first poll.
This triggers a build based on changes committed at 9:15, it starts building. 5mins later this is the poll log:
And queues up another build based on the same changes at 9:15. This is problematic because it doubles node usage, and the second build shows nothing in it's Changes log. The changes at 9:15 already successfully triggered a build into the queue, the date range of this poll should be from 9:20:58(prev) - 9:25:58(now)
When the second build starts building, this is how it gets its changelog
Where 9:21:14 is the time in which the first build finished. Thus we have this "phantom build" triggered by "no changes"
Workaround: Set polling longer interval, but this comes at the cost of responsiveness.