[rules-users] how can I modify a batch of objects

Hi all, I am trying to identify a port scan event. The basic fact is connection log. For each combination of src (source IP) and dst (destination IP) , detect a port scan event, if over 60 seconds there were at least 20 connection logs with different service and protocol. The event will stay closed for 10 minute - no event will be sent during this time for this combination of src and dst. The event will contain the connection logs' ids (markers). I tried to implement it using "accumulate" and "over window:time" but it consumes too much memory. So I am trying to imitate this functionality using several rules and facts. My drl contains the following lines (among others): declare CorrelatedEvent @role( event) @expires( 600s ) end declare CandidatesWindow @role( event) @expires( 60s ) end rule "Create Port Scan Event - 1" enabled true dialect "java" no-loop when $log : Log() not CorrelatedEvent(getId() == "portScan" , groupByFieldsMap.get("src") == $log.fieldsMap.get("src") ,groupByFieldsMap.get("dst") == $log.fieldsMap.get("dst")) $windows : ArrayList() from collect( CandidatesWindow(getRuleId() == "portScan" , groupByFieldsMap.get("src") == $log.fieldsMap.get("src") , groupByFieldsMap.get("dst") == $log.fieldsMap.get("dst"))) then String id = $log.fieldsMap.get("port").toString(); System.out.println(new Date().toString()+" windowSize: " + $windows.size()); for (Object windowObj : $windows) { CandidatesWindow window = (CandidatesWindow) windowObj; modify ( window ) { addLog($log, id) } } CandidatesWindow newWindow = new CandidatesWindow("portScan", true); newWindow.groupByFieldsMap.put("src", $log.fieldsMap.get("src")); newWindow.groupByFieldsMap.put("dst", $log.fieldsMap.get("dst")); newWindow.addLog($log, id); insert(newWindow); end This imitates sliding time windows. when I tested it, I got the following exception: Exception executing consequence for rule "Create Port Scan Event - 1" in com.checkpoint.correlation.impl.drools.package1: java.util.ConcurrentModificationException at org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1297) at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:1221) at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1456) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:710) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:674) at org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:230) at com.checkpoint.correlation.impl.drools.DroolsCEPEngineV1.insertEvents(DroolsCEPEngineV1.java:173) at com.checkpoint.correlation.impl.feeder.JsonFileFeeder.init(JsonFileFeeder.java:68) at com.checkpoint.correlation.server.CorrelationServer.initFeeder(CorrelationServer.java:63) at com.checkpoint.correlation.server.CorrelationServer.run(CorrelationServer.java:28) at com.checkpoint.correlation.server.CorrelationServer.runServer(CorrelationServer.java:101) at com.checkpoint.correlation.server.CorrelationServer.main(CorrelationServer.java:85) Caused by: java.util.ConcurrentModificationException at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:819) at java.util.ArrayList$Itr.next(ArrayList.java:791) at com.checkpoint.correlation.impl.drools.package1.Rule_Create_Port_Scan_Event___1_2f94bc67f9064c6e9614982cf9bc8859.defaultConsequence(Rule_Create_Port_Scan_Event___1_2f94bc67f9064c6e9614982cf9bc8859.java:11) at com.checkpoint.correlation.impl.drools.package1.Rule_Create_Port_Scan_Event___1_2f94bc67f9064c6e9614982cf9bc8859DefaultConsequenceInvokerGenerated.evaluate(Unknown Source) at com.checkpoint.correlation.impl.drools.package1.Rule_Create_Port_Scan_Event___1_2f94bc67f9064c6e9614982cf9bc8859DefaultConsequenceInvoker.evaluate(Unknown Source) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1287) ... 11 more It is caused by modify ( window ) in the for loop. How can I make it work? Thanks.