Hi, I hope someone can help me with this. I are running Drools 5.0.0.CR1 using JANINO to compile a spreadsheet into rules. I have lots of tests that prove the compilation is working properly and the rules are correct. Every now and then (twice in two months) we have had the following exception start appearing and the rules stop working at all. The error occurs after the system has been running for a while and at a point in the application that has been visited many many times before the error appears. Caused by: java.lang.OutOfMemoryError 2010-02-16 02:28:38,143 ERROR [STDERR] at java.util.zip.ZipFile.open(Native Method) 2010-02-16 02:28:38,143 ERROR [STDERR] at java.util.zip.ZipFile.<init>(ZipFile.java:203) 2010-02-16 02:28:38,143 ERROR [STDERR] at java.util.jar.JarFile.<init>(JarFile.java:132) 2010-02-16 02:28:38,143 ERROR [STDERR] at java.util.jar.JarFile.<init>(JarFile.java:97) 2010-02-16 02:28:38,143 ERROR [STDERR] at org .apache .catalina.loader.WebappClassLoader.openJARs(WebappClassLoader.java:1724) 2010-02-16 02:28:38,143 ERROR [STDERR] at org .apache .catalina .loader.WebappClassLoader.findResources(WebappClassLoader.java:991) 2010-02-16 02:28:38,143 ERROR [STDERR] at java.lang.ClassLoader.getResources(ClassLoader.java:1015) 2010-02-16 02:28:38,143 ERROR [STDERR] at org.drools.util.ChainedProperties.getResources(ChainedProperties.java: 155) 2010-02-16 02:28:38,143 ERROR [STDERR] at org.drools.util.ChainedProperties.<init>(ChainedProperties.java:79) 2010-02-16 02:28:38,143 ERROR [STDERR] at org.drools.util.ChainedProperties.<init>(ChainedProperties.java:41) 2010-02-16 02:28:38,143 ERROR [STDERR] at org.drools.util.ChainedProperties.<init>(ChainedProperties.java:35) 2010-02-16 02:28:38,143 ERROR [STDERR] at org.drools.SessionConfiguration.init(SessionConfiguration.java:112) 2010-02-16 02:28:38,143 ERROR [STDERR] at org.drools.SessionConfiguration.<init>(SessionConfiguration.java:106) 2010-02-16 02:28:38,143 ERROR [STDERR] at org .drools .reteoo .ReteooStatelessSession.newWorkingMemory(ReteooStatelessSession.java:86) 2010-02-16 02:28:38,143 ERROR [STDERR] at org .drools .reteoo.ReteooStatelessSession.execute(ReteooStatelessSession.java:185) 2010-02-16 02:28:38,143 ERROR [STDERR] at com .base2 .ecm.just.service.product.LocalRulesEngine.apply(LocalRulesEngine.java: 49) 2010-02-16 02:28:38,143 ERROR [STDERR] at com .base2 .ecm .just .service .product .PublishingDetailsServiceImpl .getPublishingDetails(PublishingDetailsServiceImpl.java:41) Here is the code: private static RuleBase ruleBase; public void apply(PublishingDetails publishingDetails, Advertisement advertisment) { StatelessSession statelessSession = getStatelessSession(); statelessSession.setGlobal("du",new DateUtils()); Object[] facts = {publishingDetails, advertisment}; statelessSession.execute(facts); } public void apply(Publication publication) { StatelessSession statelessSession = getStatelessSession(); statelessSession.setGlobal("du",new DateUtils()); statelessSession.execute(publication); } private StatelessSession getStatelessSession() { if (ruleBase == null) { initRuleBase(); } StatelessSession statelessSession = ruleBase.newStatelessSession(); return statelessSession; } private void initRuleBase() { Properties properties = new Properties(); properties.setProperty("drools.dialect.java.compiler", "JANINO"); PackageBuilderConfiguration conf = new PackageBuilderConfiguration(properties); PackageBuilder builder = new PackageBuilder(conf); try { SpreadsheetCompiler compiler = new SpreadsheetCompiler(); String drl = compiler.compile(getSpreadsheetStream(), InputType.XLS); builder.addPackageFromDrl(new StringReader(drl)); } catch (DroolsParserException e) { throw new RuntimeException("DroolsParserException when parsing the drools package", e); } catch (IOException e) { throw new RuntimeException("IOException when loading the drools package", e); } PackageBuilderErrors errors = builder.getErrors(); if (errors != null && !errors.isEmpty()) { for (KnowledgeBuilderError error : errors) { LOG.error(error.getMessage()); } throw new RuntimeException("There were errors in the drl file"); } Package pkg = builder.getPackage(); ruleBase = RuleBaseFactory.newRuleBase(); ruleBase.addPackage(pkg); } As I said before the loading of the rules is OK. I'm wondering if keeping a static reference to the RuleBase might be the issue? The exception looks like Drools is trying to load a jar file at runtime. Maybe there is a problem with the container (Jboss 4.2.2)? If someone could confirm that I'm not doing anything wrong by keeping a static reference to the RuleBase that would be appreciated. Note that the system runs perfectly and then starts throwing this exception with no apparent pattern to the failure. Cheers James