Hello everybody, I'm using drools 5.3.0-final to process events in stream mode with a pseudo clock. I have created an do-nothing rule as follows: rule "Do nothing" when $m : Message( ) from entry-point fromDb then end Then I add a big number of events: Calendar timestamp = new GregorianCalendar(2011, Calendar.DECEMBER, 10, 12, 0, 0); for(int i = 0;i < 100000;i++) { Message message = new Message("test", timestamp.getTime()); advanceSessionClock(pseudoClock, message.getTimestamp()); fromDb.insert(message); // <--- ksession.fireAllRules(); // <--- timestamp.add(Calendar.HOUR_OF_DAY, 1); } At the loop exit the memory usage is about 600MB. Increasing the number of events increases also the ram usage up to about 1.4GB, then it remains constant. If I don't insert the messages (lines with the comments), but I still instantiate them, at the exit of the loop, the program requires only 90MB. With the given rule, it's not necessary to store the events, so in theory the insert() should do nothing... however, when the events are inserted, it seems that drools performs a lot of useless work and allocates a lot of memory. The fact that the consumption tops at 1.4GB (a quantity much higher than the 90MB used by the messages alone) tells us that at that point the gc is triggered and that drools correctly releases the references. It seems pointless to optimize the engine for this case, but this happens also when the rules are used as "filters" between streams: rule "Filter test messages" when $m : Message( message == "test" ) from entry-point fromDb then entryPoints["testMessages"].insert($m); end rule "Only test messages" when $m : Message( ) from entry-point testMessages then end How can I decrease the memory footprint for these simple rules? -- MM -- View this message in context: http://drools.46999.n3.nabble.com/Empty-rule-and-event-retention-tp361677... Sent from the Drools: User forum mailing list archive at Nabble.com.