After upgrade to 2.73.3 we noticed that after a few days Jenkins becomes unresponsive and gives "too many open files" error. The only way to overcome the issue is to restart the instance.
The File Leak Detector Plugin does show some open handles for completed jobs but after a few hours those are pruned by themselves from the list. The total amount of open file handles never exceeds 2000 according to the plugin.
However when we run 'lsof' we see the increase of open file handles over time (see the screenshot attached: the big drop on Nov 27 is due to the manual Jenkins restart).
Here's the summary of 2 lsof runs with 1 day between them. The list of top files:
Common.groovy and BobHelper.groovy are used by some jobs.