Hello folks, I'm experiencing some odd behaviour from Drools (or maybe the Eclipse compiler) when load-testing my application, and wondered if anyone else had experienced the same issue. I have a web service which, for every request, loads in rules from the database, creates a org.drools.lang.descr.PackageDescr and then uses this to create a org.drools.rule.Package. The code is something like: PackageBuilderConfiguration conf = new PackageBuilderConfiguration(); PackageBuilder builder = new PackageBuilder(conf); PackageDescr packageDescr = new PackageDescr("MyRulebaseName"); populatePackageDescr(packageDescr); builder.addPackage(packageDescr); Package _package = builder.getPackage(); return _package; This code gets run every request. The populatePackageDescr() method adds imports, globals, functions and rules to the PackageDescr. My load-test just repeatedly calls the same rulebase, so populatePackageDescr() will be doing exactly the same thing for each request. Occasionally (normally once or twice per 100 requests) I get a rule compilation error (the exact error varies from request to request) whereas most of the time the same rule compiles fine. This makes me suspect a thread-safety issue in either the PackageBuilder or the compiler (I'm using the eclipse compiler). Initially, I suspected a problem in my populatePackageDescr(packageDescr) method, but I think I've ruled this out. There is nothing stateful in this method, and I've tried dumping the XML representation of the packageDescr immediately after populating it; it looks fine to me and is exactly the same whether compilation succeeds or and fails. Has anyone done this kind of thing successfully under a heavy load? Thanks, Dean.