[rules-users] Changing rules at runtime

[Felipe Piccolini]

We are working on a solution using Topic JMS with spring, so we build  
a RuleBase and
publish it as a 'post' with one topic, while the 'client' which is a  
WorkingMemoryFactory is
listening on the topic all the time (configurable) so when the topic  
is refreshed, the client
automagicaly refresh his own -singleton- RuleBase and (as is a  
Factory) is able to returns
a newWorkingMemory from that RuleBase. We will send the code with  
examples in few
weeks, I think.

Good Luck.

On 21-03-2007, at 9:01, jdepaul wrote:

>
> 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:
>>
>>> We want to change rules at runtime without redeploying the whole
>>> application.
>
> -- 
> 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.
>
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Felipe Piccolini M.
felipe.piccolini at bluesoft.cl




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