KnowledgeBuilderImpl.add(...) throws org.mvel2.CompileException when executed concurrently for the same resource ---------------------------------------------------------------------------------------------------------------- Key: JBRULES-2380 URL: https://jira.jboss.org/jira/browse/JBRULES-2380 Project: Drools Issue Type: Quality Risk Security Level: Public(Everyone can see) Components: drools-compiler Environment: Drools 5.0.1 core 2 duo @ 2.6 ghz, win xp prof sp3, sun jdk 1.6.0_17 Pentium Dual CPU E2160 @ 1.8GHz, XP prof SP3, sun jdk 1.6.0_16. Reporter: Grigoriy Grigoriev Assignee: Edson Tirelli Fix For: 5.1.0.M2 Attachments: droolsKnowledgeTest.zip Let us assume a multithreaded application, that tries to initialise & start several processes using a StatefulKnowledgeSession in order to use in these processes rule flow. The flow in all the processes is the same but every process instance must have an own StatefulKnowledgeSession instance because of stateful session. Actually the problem: At the initializing phase occurs an org.mvel2.CompileException exception from time to time at KnowledgeBuilder.add(...): Exception in thread "Thread-60" [Error: incomplete statement: (possible use of reserved keyword as identifier: )] [Near : {... globals != empt ....}] ^ [Line: 0, Column: 0] at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:153) at org.mvel2.MVELInterpretedRuntime.parse(MVELInterpretedRuntime.java:44) at org.mvel2.MVEL.eval(MVEL.java:514) at org.mvel2.templates.res.IfNode.eval(IfNode.java:61) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:39) at org.mvel2.templates.res.ForEachNode.eval(ForEachNode.java:116) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:39) at org.mvel2.templates.res.IfNode.eval(IfNode.java:64) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:195) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:190) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:180) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:169) at org.drools.rule.builder.dialect.java.AbstractJavaRuleBuilder.generatTemplates(AbstractJavaRuleBuilder.java:126) at org.drools.rule.builder.dialect.java.JavaConsequenceBuilder.build(JavaConsequenceBuilder.java:128) at org.drools.rule.builder.RuleBuilder.build(RuleBuilder.java:86) at org.drools.compiler.PackageBuilder.addRule(PackageBuilder.java:1159) at org.drools.compiler.PackageBuilder.addPackage(PackageBuilder.java:649) at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:290) at org.drools.compiler.PackageBuilder.addKnowledgeResource(PackageBuilder.java:488) at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:25) at com.myfirm.RuleFlowProcess.init(RuleFlowProcess.java:25) at com.myfirm.RuleFlowProcess.clone(RuleFlowProcess.java:53) at com.myfirm.ThreadTest$CloneThread.run(ThreadTest.java:35) Caused by: java.lang.NullPointerException at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:113) ... 27 more Exception in thread "Thread-72" [Error: incomplete statement: (possible use of reserved keyword as identifier: )] [Near : {... declarations != empt ....}] ^ [Line: 0, Column: 0] at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:153) at org.mvel2.MVELInterpretedRuntime.parse(MVELInterpretedRuntime.java:44) at org.mvel2.MVEL.eval(MVEL.java:514) at org.mvel2.templates.res.IfNode.eval(IfNode.java:61) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:39) at org.mvel2.templates.res.ForEachNode.eval(ForEachNode.java:116) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:39) at org.mvel2.templates.res.ForEachNode.eval(ForEachNode.java:116) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:195) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:190) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:180) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:169) at org.drools.rule.builder.dialect.java.AbstractJavaRuleBuilder.generatTemplates(AbstractJavaRuleBuilder.java:135) at org.drools.rule.builder.dialect.java.JavaConsequenceBuilder.build(JavaConsequenceBuilder.java:128) at org.drools.rule.builder.RuleBuilder.build(RuleBuilder.java:86) at org.drools.compiler.PackageBuilder.addRule(PackageBuilder.java:1159) at org.drools.compiler.PackageBuilder.addPackage(PackageBuilder.java:649) at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:290) at org.drools.compiler.PackageBuilder.addKnowledgeResource(PackageBuilder.java:488) at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:25) at com.myfirm.RuleFlowProcess.init(RuleFlowProcess.java:25) at com.myfirm.RuleFlowProcess.clone(RuleFlowProcess.java:53) at com.myfirm.ThreadTest$CloneThread.run(ThreadTest.java:35) Caused by: java.lang.NullPointerException at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:113) ... 33 more To demonstrate this problem I have created a simple test maven project that reproduces this error (s. attach): I have a class that creates & inits stateful knowledge session in a init method (RuleFlowProcess): /** * inits the rule flow */ public class RuleFlowProcess { private StatefulKnowledgeSession ksession; public void init() { KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); kbuilder.add(ResourceFactory.newClassPathResource("threadSafeTest.rf"), ResourceType.DRF); kbuilder.add(ResourceFactory.newClassPathResource("testRules1.drl"), ResourceType.DRL); kbuilder.add(ResourceFactory.newClassPathResource("testRules2.drl"), ResourceType.DRL); kbuilder.add(ResourceFactory.newClassPathResource("testRules3.drl"), ResourceType.DRL); kbuilder.add(ResourceFactory.newClassPathResource("testRules4.drl"), ResourceType.DRL); KnowledgeBuilderErrors errors = kbuilder.getErrors(); if (errors.size() > 0) { StringBuilder errorString = new StringBuilder(); for (KnowledgeBuilderError error : errors) { errorString.append(error); } throw new RuntimeException(errorString.toString()); } KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase(); kbase.addKnowledgePackages(kbuilder.getKnowledgePackages()); ksession = kbase.newStatefulKnowledgeSession(); } ... } I create & init concurrently in several (200) threads this RuleFlowProcess and some threads crash with this exceptions while adding the resources.

KnowledgeBuilderImpl.add(...) throws org.mvel2.CompileException when executed concurrently for the same resource ---------------------------------------------------------------------------------------------------------------- Key: JBRULES-2380 URL: https://jira.jboss.org/browse/JBRULES-2380 Project: Drools Issue Type: Quality Risk Security Level: Public(Everyone can see) Components: drools-compiler Environment: Drools 5.0.1 core 2 duo @ 2.6 ghz, win xp prof sp3, sun jdk 1.6.0_17 Pentium Dual CPU E2160 @ 1.8GHz, XP prof SP3, sun jdk 1.6.0_16. Reporter: Grigoriy Grigoriev Assignee: Edson Tirelli Fix For: 5.1.0 Attachments: droolsKnowledgeTest.zip Let us assume a multithreaded application, that tries to initialise & start several processes using a StatefulKnowledgeSession in order to use in these processes rule flow. The flow in all the processes is the same but every process instance must have an own StatefulKnowledgeSession instance because of stateful session. Actually the problem: At the initializing phase occurs an org.mvel2.CompileException exception from time to time at KnowledgeBuilder.add(...): Exception in thread "Thread-60" [Error: incomplete statement: (possible use of reserved keyword as identifier: )] [Near : {... globals != empt ....}] ^ [Line: 0, Column: 0] at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:153) at org.mvel2.MVELInterpretedRuntime.parse(MVELInterpretedRuntime.java:44) at org.mvel2.MVEL.eval(MVEL.java:514) at org.mvel2.templates.res.IfNode.eval(IfNode.java:61) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:39) at org.mvel2.templates.res.ForEachNode.eval(ForEachNode.java:116) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:39) at org.mvel2.templates.res.IfNode.eval(IfNode.java:64) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:195) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:190) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:180) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:169) at org.drools.rule.builder.dialect.java.AbstractJavaRuleBuilder.generatTemplates(AbstractJavaRuleBuilder.java:126) at org.drools.rule.builder.dialect.java.JavaConsequenceBuilder.build(JavaConsequenceBuilder.java:128) at org.drools.rule.builder.RuleBuilder.build(RuleBuilder.java:86) at org.drools.compiler.PackageBuilder.addRule(PackageBuilder.java:1159) at org.drools.compiler.PackageBuilder.addPackage(PackageBuilder.java:649) at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:290) at org.drools.compiler.PackageBuilder.addKnowledgeResource(PackageBuilder.java:488) at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:25) at com.myfirm.RuleFlowProcess.init(RuleFlowProcess.java:25) at com.myfirm.RuleFlowProcess.clone(RuleFlowProcess.java:53) at com.myfirm.ThreadTest$CloneThread.run(ThreadTest.java:35) Caused by: java.lang.NullPointerException at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:113) ... 27 more Exception in thread "Thread-72" [Error: incomplete statement: (possible use of reserved keyword as identifier: )] [Near : {... declarations != empt ....}] ^ [Line: 0, Column: 0] at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:153) at org.mvel2.MVELInterpretedRuntime.parse(MVELInterpretedRuntime.java:44) at org.mvel2.MVEL.eval(MVEL.java:514) at org.mvel2.templates.res.IfNode.eval(IfNode.java:61) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:39) at org.mvel2.templates.res.ForEachNode.eval(ForEachNode.java:116) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:39) at org.mvel2.templates.res.ForEachNode.eval(ForEachNode.java:116) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:195) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:190) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:180) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:169) at org.drools.rule.builder.dialect.java.AbstractJavaRuleBuilder.generatTemplates(AbstractJavaRuleBuilder.java:135) at org.drools.rule.builder.dialect.java.JavaConsequenceBuilder.build(JavaConsequenceBuilder.java:128) at org.drools.rule.builder.RuleBuilder.build(RuleBuilder.java:86) at org.drools.compiler.PackageBuilder.addRule(PackageBuilder.java:1159) at org.drools.compiler.PackageBuilder.addPackage(PackageBuilder.java:649) at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:290) at org.drools.compiler.PackageBuilder.addKnowledgeResource(PackageBuilder.java:488) at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:25) at com.myfirm.RuleFlowProcess.init(RuleFlowProcess.java:25) at com.myfirm.RuleFlowProcess.clone(RuleFlowProcess.java:53) at com.myfirm.ThreadTest$CloneThread.run(ThreadTest.java:35) Caused by: java.lang.NullPointerException at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:113) ... 33 more To demonstrate this problem I have created a simple test maven project that reproduces this error (s. attach): I have a class that creates & inits stateful knowledge session in a init method (RuleFlowProcess): /** * inits the rule flow */ public class RuleFlowProcess { private StatefulKnowledgeSession ksession; public void init() { KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); kbuilder.add(ResourceFactory.newClassPathResource("threadSafeTest.rf"), ResourceType.DRF); kbuilder.add(ResourceFactory.newClassPathResource("testRules1.drl"), ResourceType.DRL); kbuilder.add(ResourceFactory.newClassPathResource("testRules2.drl"), ResourceType.DRL); kbuilder.add(ResourceFactory.newClassPathResource("testRules3.drl"), ResourceType.DRL); kbuilder.add(ResourceFactory.newClassPathResource("testRules4.drl"), ResourceType.DRL); KnowledgeBuilderErrors errors = kbuilder.getErrors(); if (errors.size() > 0) { StringBuilder errorString = new StringBuilder(); for (KnowledgeBuilderError error : errors) { errorString.append(error); } throw new RuntimeException(errorString.toString()); } KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase(); kbase.addKnowledgePackages(kbuilder.getKnowledgePackages()); ksession = kbase.newStatefulKnowledgeSession(); } ... } I create & init concurrently in several (200) threads this RuleFlowProcess and some threads crash with this exceptions while adding the resources.

KnowledgeBuilderImpl.add(...) throws org.mvel2.CompileException when executed concurrently for the same resource ---------------------------------------------------------------------------------------------------------------- Key: JBRULES-2380 URL: https://issues.jboss.org/browse/JBRULES-2380 Project: Drools Issue Type: Quality Risk Security Level: Public(Everyone can see) Components: drools-compiler Environment: Drools 5.0.1 core 2 duo @ 2.6 ghz, win xp prof sp3, sun jdk 1.6.0_17 Pentium Dual CPU E2160 @ 1.8GHz, XP prof SP3, sun jdk 1.6.0_16. Reporter: Grigoriy Grigoriev Assignee: Edson Tirelli Labels: multithreading Fix For: 5.2.0.CR1 Attachments: droolsKnowledgeTest.zip Let us assume a multithreaded application, that tries to initialise & start several processes using a StatefulKnowledgeSession in order to use in these processes rule flow. The flow in all the processes is the same but every process instance must have an own StatefulKnowledgeSession instance because of stateful session. Actually the problem: At the initializing phase occurs an org.mvel2.CompileException exception from time to time at KnowledgeBuilder.add(...): Exception in thread "Thread-60" [Error: incomplete statement: (possible use of reserved keyword as identifier: )] [Near : {... globals != empt ....}] ^ [Line: 0, Column: 0] at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:153) at org.mvel2.MVELInterpretedRuntime.parse(MVELInterpretedRuntime.java:44) at org.mvel2.MVEL.eval(MVEL.java:514) at org.mvel2.templates.res.IfNode.eval(IfNode.java:61) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:39) at org.mvel2.templates.res.ForEachNode.eval(ForEachNode.java:116) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:39) at org.mvel2.templates.res.IfNode.eval(IfNode.java:64) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:195) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:190) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:180) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:169) at org.drools.rule.builder.dialect.java.AbstractJavaRuleBuilder.generatTemplates(AbstractJavaRuleBuilder.java:126) at org.drools.rule.builder.dialect.java.JavaConsequenceBuilder.build(JavaConsequenceBuilder.java:128) at org.drools.rule.builder.RuleBuilder.build(RuleBuilder.java:86) at org.drools.compiler.PackageBuilder.addRule(PackageBuilder.java:1159) at org.drools.compiler.PackageBuilder.addPackage(PackageBuilder.java:649) at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:290) at org.drools.compiler.PackageBuilder.addKnowledgeResource(PackageBuilder.java:488) at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:25) at com.myfirm.RuleFlowProcess.init(RuleFlowProcess.java:25) at com.myfirm.RuleFlowProcess.clone(RuleFlowProcess.java:53) at com.myfirm.ThreadTest$CloneThread.run(ThreadTest.java:35) Caused by: java.lang.NullPointerException at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:113) ... 27 more Exception in thread "Thread-72" [Error: incomplete statement: (possible use of reserved keyword as identifier: )] [Near : {... declarations != empt ....}] ^ [Line: 0, Column: 0] at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:153) at org.mvel2.MVELInterpretedRuntime.parse(MVELInterpretedRuntime.java:44) at org.mvel2.MVEL.eval(MVEL.java:514) at org.mvel2.templates.res.IfNode.eval(IfNode.java:61) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:39) at org.mvel2.templates.res.ForEachNode.eval(ForEachNode.java:116) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:39) at org.mvel2.templates.res.ForEachNode.eval(ForEachNode.java:116) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:195) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:190) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:180) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:169) at org.drools.rule.builder.dialect.java.AbstractJavaRuleBuilder.generatTemplates(AbstractJavaRuleBuilder.java:135) at org.drools.rule.builder.dialect.java.JavaConsequenceBuilder.build(JavaConsequenceBuilder.java:128) at org.drools.rule.builder.RuleBuilder.build(RuleBuilder.java:86) at org.drools.compiler.PackageBuilder.addRule(PackageBuilder.java:1159) at org.drools.compiler.PackageBuilder.addPackage(PackageBuilder.java:649) at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:290) at org.drools.compiler.PackageBuilder.addKnowledgeResource(PackageBuilder.java:488) at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:25) at com.myfirm.RuleFlowProcess.init(RuleFlowProcess.java:25) at com.myfirm.RuleFlowProcess.clone(RuleFlowProcess.java:53) at com.myfirm.ThreadTest$CloneThread.run(ThreadTest.java:35) Caused by: java.lang.NullPointerException at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:113) ... 33 more To demonstrate this problem I have created a simple test maven project that reproduces this error (s. attach): I have a class that creates & inits stateful knowledge session in a init method (RuleFlowProcess): /** * inits the rule flow */ public class RuleFlowProcess { private StatefulKnowledgeSession ksession; public void init() { KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); kbuilder.add(ResourceFactory.newClassPathResource("threadSafeTest.rf"), ResourceType.DRF); kbuilder.add(ResourceFactory.newClassPathResource("testRules1.drl"), ResourceType.DRL); kbuilder.add(ResourceFactory.newClassPathResource("testRules2.drl"), ResourceType.DRL); kbuilder.add(ResourceFactory.newClassPathResource("testRules3.drl"), ResourceType.DRL); kbuilder.add(ResourceFactory.newClassPathResource("testRules4.drl"), ResourceType.DRL); KnowledgeBuilderErrors errors = kbuilder.getErrors(); if (errors.size() > 0) { StringBuilder errorString = new StringBuilder(); for (KnowledgeBuilderError error : errors) { errorString.append(error); } throw new RuntimeException(errorString.toString()); } KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase(); kbase.addKnowledgePackages(kbuilder.getKnowledgePackages()); ksession = kbase.newStatefulKnowledgeSession(); } ... } I create & init concurrently in several (200) threads this RuleFlowProcess and some threads crash with this exceptions while adding the resources.

KnowledgeBuilderImpl.add(...) throws org.mvel2.CompileException when executed concurrently for the same resource ---------------------------------------------------------------------------------------------------------------- Key: JBRULES-2380 URL: https://issues.jboss.org/browse/JBRULES-2380 Project: Drools Issue Type: Quality Risk Security Level: Public(Everyone can see) Components: drools-compiler Environment: Drools 5.0.1 core 2 duo @ 2.6 ghz, win xp prof sp3, sun jdk 1.6.0_17 Pentium Dual CPU E2160 @ 1.8GHz, XP prof SP3, sun jdk 1.6.0_16. Reporter: Grigoriy Grigoriev Assignee: Mark Proctor Labels: multithreading Fix For: 5.2.0.CR1 Attachments: droolsKnowledgeTest.zip Let us assume a multithreaded application, that tries to initialise & start several processes using a StatefulKnowledgeSession in order to use in these processes rule flow. The flow in all the processes is the same but every process instance must have an own StatefulKnowledgeSession instance because of stateful session. Actually the problem: At the initializing phase occurs an org.mvel2.CompileException exception from time to time at KnowledgeBuilder.add(...): Exception in thread "Thread-60" [Error: incomplete statement: (possible use of reserved keyword as identifier: )] [Near : {... globals != empt ....}] ^ [Line: 0, Column: 0] at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:153) at org.mvel2.MVELInterpretedRuntime.parse(MVELInterpretedRuntime.java:44) at org.mvel2.MVEL.eval(MVEL.java:514) at org.mvel2.templates.res.IfNode.eval(IfNode.java:61) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:39) at org.mvel2.templates.res.ForEachNode.eval(ForEachNode.java:116) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:39) at org.mvel2.templates.res.IfNode.eval(IfNode.java:64) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:195) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:190) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:180) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:169) at org.drools.rule.builder.dialect.java.AbstractJavaRuleBuilder.generatTemplates(AbstractJavaRuleBuilder.java:126) at org.drools.rule.builder.dialect.java.JavaConsequenceBuilder.build(JavaConsequenceBuilder.java:128) at org.drools.rule.builder.RuleBuilder.build(RuleBuilder.java:86) at org.drools.compiler.PackageBuilder.addRule(PackageBuilder.java:1159) at org.drools.compiler.PackageBuilder.addPackage(PackageBuilder.java:649) at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:290) at org.drools.compiler.PackageBuilder.addKnowledgeResource(PackageBuilder.java:488) at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:25) at com.myfirm.RuleFlowProcess.init(RuleFlowProcess.java:25) at com.myfirm.RuleFlowProcess.clone(RuleFlowProcess.java:53) at com.myfirm.ThreadTest$CloneThread.run(ThreadTest.java:35) Caused by: java.lang.NullPointerException at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:113) ... 27 more Exception in thread "Thread-72" [Error: incomplete statement: (possible use of reserved keyword as identifier: )] [Near : {... declarations != empt ....}] ^ [Line: 0, Column: 0] at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:153) at org.mvel2.MVELInterpretedRuntime.parse(MVELInterpretedRuntime.java:44) at org.mvel2.MVEL.eval(MVEL.java:514) at org.mvel2.templates.res.IfNode.eval(IfNode.java:61) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:39) at org.mvel2.templates.res.ForEachNode.eval(ForEachNode.java:116) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:39) at org.mvel2.templates.res.ForEachNode.eval(ForEachNode.java:116) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.res.ExpressionNode.eval(ExpressionNode.java:53) at org.mvel2.templates.res.TextNode.eval(TextNode.java:46) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:195) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:190) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:180) at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:169) at org.drools.rule.builder.dialect.java.AbstractJavaRuleBuilder.generatTemplates(AbstractJavaRuleBuilder.java:135) at org.drools.rule.builder.dialect.java.JavaConsequenceBuilder.build(JavaConsequenceBuilder.java:128) at org.drools.rule.builder.RuleBuilder.build(RuleBuilder.java:86) at org.drools.compiler.PackageBuilder.addRule(PackageBuilder.java:1159) at org.drools.compiler.PackageBuilder.addPackage(PackageBuilder.java:649) at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:290) at org.drools.compiler.PackageBuilder.addKnowledgeResource(PackageBuilder.java:488) at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:25) at com.myfirm.RuleFlowProcess.init(RuleFlowProcess.java:25) at com.myfirm.RuleFlowProcess.clone(RuleFlowProcess.java:53) at com.myfirm.ThreadTest$CloneThread.run(ThreadTest.java:35) Caused by: java.lang.NullPointerException at org.mvel2.MVELInterpretedRuntime.parseAndExecuteInterpreted(MVELInterpretedRuntime.java:113) ... 33 more To demonstrate this problem I have created a simple test maven project that reproduces this error (s. attach): I have a class that creates & inits stateful knowledge session in a init method (RuleFlowProcess): /** * inits the rule flow */ public class RuleFlowProcess { private StatefulKnowledgeSession ksession; public void init() { KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); kbuilder.add(ResourceFactory.newClassPathResource("threadSafeTest.rf"), ResourceType.DRF); kbuilder.add(ResourceFactory.newClassPathResource("testRules1.drl"), ResourceType.DRL); kbuilder.add(ResourceFactory.newClassPathResource("testRules2.drl"), ResourceType.DRL); kbuilder.add(ResourceFactory.newClassPathResource("testRules3.drl"), ResourceType.DRL); kbuilder.add(ResourceFactory.newClassPathResource("testRules4.drl"), ResourceType.DRL); KnowledgeBuilderErrors errors = kbuilder.getErrors(); if (errors.size() > 0) { StringBuilder errorString = new StringBuilder(); for (KnowledgeBuilderError error : errors) { errorString.append(error); } throw new RuntimeException(errorString.toString()); } KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase(); kbase.addKnowledgePackages(kbuilder.getKnowledgePackages()); ksession = kbase.newStatefulKnowledgeSession(); } ... } I create & init concurrently in several (200) threads this RuleFlowProcess and some threads crash with this exceptions while adding the resources.