The following rule produces a memory leak in Drools 6.1.0-SNAPSHOT: (Stream mode) declare MyEvent @role(event) @timestamp(timestamp) end /* If a RAISE is buffered for N seconds, send it out */ rule "forward raise" no-loop duration (3s) when $raise : MyEvent(eventState == EventState.RAISE, $raiseId : eventId) then System.out.println("Forwarding RAISE(" + $raiseId + ")"); delete($raise); end I see the rule fire as expected, printing out the message 3 seconds after the event is added into the session. While the event is waiting, I see a FactCount of 1 in the session. After the rule fires, the fact count goes to 0. However, using JVisualVm, querying the heap dump shows 1 instance of MyEvent, referenced by an EventFactHandle and several other Drools objects. Is this a bug, or is there a better way to write this rule so Drools’ internals let go of the object after it is no longer a fact?