Re: [rules-users] Changing rules at runtime

I don't have an application in PROD yet, I'm just working on a Proof of Concept with Drools 3.1.0M1 and Spring 1.2.8 but I have a similar situation as you in that I'll need to periodically reload Rules without restarting the App. This is what I've discover will work for us - not sure in your case, but here it is: I have objects called EventRuleBase objects which basically wrap RuleBase objects. Each instance of EventRuleBase object is tied to a resource (*.drl file on the file system for now, but in the future it may come from a DB). I then have a notion of RuleBaseManager object which is in charge of managing the collection of EventRuleBase objects. I use Spring to initialize and load all EventRuleBase objects individually and then register themselves with the RuleBaseManager object which records their instances in HashMap. The RuleBaseManager implements several methods: getWorkingMemory(...) and ruleChange(newEventRuleBase). The RuleBaseManager is a Singleton and the EventRuleBase objects are NOT singletons.... In my testing, I've discovered that when it's time to reload rules (some type of triggering mechanism must invoke this), I can ask Spring for a new instance of the EventRuleBase object by name (i.e. appContext.getBean(LOAD_rulebase) - it will fetch a brand new object which it will automatically reload from the underlying Resource (on the filesystem) - note that "singleton=false" bean configuration in Spring config is key for this. I can then hand the new instance of the new EventRuleBase object to the ruleChange(newEventRuleBase) method which it will then synchronize and 'swap-in' the new object into the HashMap it maintains. The clients that invoke subsequent getNewWorkingMemory() methods on the new EventRuleBase object will then start getting references to new object with NEW rules. I figured I'll need to protect the integrity of the hashmap using the JDK 1.5 implementation of ConcurrentHashMap which is very much possible using Spring 2.x - check out the documentation. Hope this helps. Regards - James' Carlos Henriquez wrote: -- View this message in context: http://www.nabble.com/Changing-rules-at-runtime-tf3392187.html#a9593359 Sent from the drools - user mailing list archive at Nabble.com.