Stateful session is not thread safe for update operation on JDK11 ----------------------------------------------------------------- Key: DROOLS-3385 URL: https://issues.jboss.org/browse/DROOLS-3385 Project: Drools Issue Type: Bug Components: core engine Affects Versions: 7.16.0.Final Reporter: Radovan Synek Assignee: Mario Fusco Priority: Critical We have a test failure in multithreaded solving in OptaPlanner (please see the linked issue for details). Interestingly, it happens only with JDK11. java.util.ConcurrentModificationException: null at java.base/java.util.HashMap.computeIfAbsent(HashMap.java:1134) at org.drools.core.impl.KnowledgeBaseImpl.getOrCreateExactTypeDeclaration(KnowledgeBaseImpl.java:1458) at org.drools.core.common.NamedEntryPoint.update(NamedEntryPoint.java:324) at org.drools.core.impl.StatefulKnowledgeSessionImpl.update(StatefulKnowledgeSessionImpl.java:1570) at org.optaplanner.core.impl.score.director.drools.DroolsScoreDirector.update(DroolsScoreDirector.java:254)