Had a report recently that our QA application servers kept falling over (Glassfish that is, not the hardware).    Started looking into it today, couldn’t find a sign of anything wrong.  Then one of the lead developers added a comment about how they’d seen this behaviour when the default Glassfish debug port (9009) gets pinged by our monitoring system.  Then the developer who reported the problem commented ‘oh yeah, we turned that on on Sunday’.

Gotta love trying to work out why something is crashing when no one has said that the configuration has been changed (and the other implementations are perfectly stable).

Note to self: tripwire those machines.