We have multiple threads performing inserts/updates/queries/fireAllRules and had to synchronize access on working memory.  The performance impact is surprisingly almost non-existent.

From: rules-dev-bounces@lists.jboss.org [mailto:rules-dev-bounces@lists.jboss.org] On Behalf Of Anstis, Michael (M.)
Sent: Monday, July 14, 2008 9:24 AM
To: Rules Dev List
Subject: RE: [rules-dev] Multi threading usage best practice

Hi,
 
Would synchronising on working memory effectively serialise the effects of fireAllRules()?
...
synchronised(wm) {
    wm.fireAllRules();
}
...
I don't know whether this would kill your through-put either.
 
Cheers,
 
Mike

From: rules-dev-bounces@lists.jboss.org [mailto:rules-dev-bounces@lists.jboss.org] On Behalf Of 9Lives 9Lives
Sent: 14 July 2008 13:41
To: rules-dev@lists.jboss.org
Subject: [rules-dev] Multi threading usage best practice

Hello
 
I'm using Drools 4.0.7 inside a mail relay application 2 determine the operations that need 2 b executed on each passing message.
To do this i'm using the following scenario:
  1. I have a ruleBase.newStatefulSession().
  2. I have a fixed set of facts.
  3. I have a fixed set of rules.
  4. Each mailer (a thread that is handling a single message) is inserting the message to the working memory, calls the "fireAllRules" method and retracts the message.
  5. Rules that r executed change custom attributes in the message.
Problem:
I noticed that sometimes a rule can b executed on the same message more then once.
 
Assumption:
My guess is that because i'm working is a multi threading environment but using a stateful session, what happens is:
  1. Thread A is inserting Message A.
  2. Thread B is inserting Message B
  3. Thread A is calling fireAllRules
  4. Rule X is executed on messages A + B.
  5. Thread B is calling fireAllRules
  6. Rule X is executed on messages A + B
  7. Thread A is retracting Message A
  8. Thread B is retracting message B
Question:
My goal is 2 make sure a rule is executed only once on a single message.
Any ideas on how 2 avoid the situation described above?
 
TnX
Dotan
 
 

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