Approach to reuse KieSession

[sumit dhaniya]

I'm working on a highly concurrent application in which I need to execute rules for lots of user requests. Creating a new object of KieSession for each request was taking too much time and contributing to GC due to which I started reusing couple of KieSession by deleting all the facts after execution of all rules. Can you please confirm if there's any pitfalls in using this approach.

Please find the code snippet below :-

private Map<Object, KieSession> kieSessionMap = new HashMap<>();


public void ruleMethod(A a) {
        KieSession kieSession = null;
        if (kieSessionMap.get(Thread.currentThread()) != null) {
            kieSession = kieSessionMap.get(Thread.currentThread());
        } else {
            kieSession = sortingWeightageKB.newKieSession();
            kieSessionMap.put(Thread.currentThread(), kieSession);
        }


       for (RuleFactor ruleFactor : ruleFactors) {
            kieSession.insert(ruleFactor);
        }
        kieSession.fireAllRules();
        for (FactHandle factHandle : kieSession.getFactHandles()) {
            kieSession.delete(factHandle);
        }
}

[David W]

The main issue with this approach is that each user will use the same (default) KieBase. The kie base contains all the rules, globals etc so every user will execute every user's rules. You probably dont want that.

If you want each user to only execute their own rules, you need to create and save a KieBase for each user too.

David.

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[sumit dhaniya]

Rules are not specific to particular user ,checks are in the rules based on user profile which I insert before execution of rules and delete from session after execution . I'm not keeping any global variables.

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[Gergely Bacsó]

Hi Sumit,

We just ran into a similar situation where we have been using very short-lived sessions with very high-frequency. After doing some profiling we found out that around half of the the time we previously assumed to be used for "Drools processing" was in fact spent on "Initializing new kie session". Checking the internals it turned out that the thread was doing loads of loading and searching via classloaders, mostly to obtain a new KnowledgeSessionConfiguration.

SOLUTION:
instead of:

initializing the container like this:

        kieContainer = kieServices.newKieContainer(releaseId);

and repeatedly calling this:

        return kieContainer.newKieSession(KIE_SESSION_ID);

we should:

initialize like this:

        kieContainer = kieServices.newKieContainer(releaseId);
        kieEnvironment = kieServices.newEnvironment();
        kieSessionConfiguration = kieServices.newKieSessionConfiguration();

and get new sessions like this:

        return kieContainer.newKieSession(KIE_SESSION_ID, kieEnvironment, kieSessionConfiguration);

This is a non-intrusive change which I believe is much safer to do than cleaning up and re-allocating previously used sessions. The effect of this change in terms of performance is substantial.

Cheers,
Gergely

[Matteo Mortari]

Hi, I also have one similar scenario for high-frequency session needs: basically to perform reasoning over Messages received for filtering, processing, etc.

But instead of "reusing couple of KieSession by deleting all the facts after execution of all rules" I basically use StatelessKieSession created ad-hoc for each Message instance; I'm not sure if you have considered this option for your use-case scenario too.

Maybe you did and cannot be applied because you need to get hold of some state-facts across a few calls; I thought however worth mentioning, in case this was missed.

Ciao,

MM

[David Weir]

Have you thought about storing the KieSession (using the marshaller) and retrieving it (using unmarshaller) for each user, rather than creating one each time?

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[Nest]

Hi,

   I'm facing a problem in this line of code:
   return kieContainer.newKieSession(KIE_SESSION_ID, kieEnvironment, kieSessionConfiguration);
 
   what is KIE_SESSION_ID, if it is kieSessionId so how can i get it. I have used the following line of code but it always return me 0, after that if I'm trying to initialize with this id but it's not working.

     KieSession objKieSession = kieContainer.newKieSession(); 
     objKieSession.getId()

regards,
Nest

[Mark Proctor]

The searching of the KnowledgeSessionConfiguration is probably a regression, at some point this was cached for a given KieBase. We’ll look into fixing this for 6.3. Can you open a JIRA?

Mark

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[Nest]

Hi Gergely,

   I'm facing a problem in this line of code:
   return kieContainer.newKieSession(

KIE_SESSION_ID, kieEnvironment, kieSessionConfiguration);
 
   what is KIE_SESSION_ID, if it is kieSessionId so how can i get it. I have used the following line of code but it always return me 0, after that if I'm trying to initialize with this id but it's not working.

     KieSession objKieSession = kieContainer.newKieSession(); 
     objKieSession.getId()

regards,
Nest

[dhivakaran padmanabhan]

Hi,

Is the above suggested issue fixed ???

Thanks
Dhiva

[Sushil Kumar]

Hi,

I have tried below solution but not able to create kieServices.newEnvironment(); as getting below error:

Unable to evaluate the expression Method threw 'java.lang.UnsupportedOperationException' exception.

so can you help me here

On Wednesday, February 18, 2015 at 6:29:22 PM UTC+5:30, Gergely Bacsó wrote: