[rules-users] Sessions Sharing KnowledgeBase
malkhafaji
moe.alkhafaji at medcpu.com
Tue Dec 22 11:24:38 EST 2009
Edson,
Thank you for replying to my question. I haven't tried the new release since
May 19th of this year. Are you talking about the binaries (Drools 5.1.0.M1
Binaries)? Should I go ahead and try that?
To answer your question about not sharing KnowledgeBase for all requests, we
have a very advanced logic outside of the rules engine. To give you some
flavor, we have only one type of object per request. Each request will have
its own data in that object. Now, we have wrapper code around the engine to
do things like:
1. Last time this engine ran for this object, including what rules executed,
etc.
2. Rules within packages loaded by default may load other packages on the
fly because of which rules executed, and this only applies to that object
that triggered the loading of those packages. For example, by default we
have 1 package that is used for all objects. But object A may trigger a rule
that loads another package which becomes available to it besides the main
one. However, this new package is not yet available to all other objects.
So, I did not know how I can load packages but only make them visible to
some of the objects that I push through the session's knowledge base.
3. Our rules engine is either data driven (and the notification does not
come from the rule, but outside the rule in some common logic), or time
driven (run the engine again after n minutes because that is when our logic
has determined that one of the conditions would turn true on a previously
false condition potentially starting a chain of executions), etc.
And other things. So, I found it to be much easier for me and my sanity to
start using a new instance of a session (having its own knowledge base) per
request. Those requests are very small and take no more than milliseconds on
each object. So, I am using a stateful session that is alive for the life of
the respective object. My objects are finite (you cannot have more than
1,000 in our memory), and they and their respective instances are very light
weight and do not need more than a 1 GB of memory (mostly hovers around
500-600 MB).
I am sure there are many ways to get it working on a sharing knowledge base,
I just thought this way I don't need to worry about synchronizations or any
other complicated logic on top of what we have. So, I made the decision.
Please confirm that M1 binaries has your latest fix so I can get testing on
it. Thanks!
Edson Tirelli-4 wrote:
>
> Hi,
>
> I fixed a problem related to deadlock when sharing packages among
> multiple kbases a couple weeks ago. Not sure if it is the same, but try
> trunk and let me know, plz.
>
> Meanwhile, I am curious why you can't simply create a kbase with all
> your
> rules and share the kbase among all your requests, just creating one
> session
> per request?
>
> Reason is that adding packages to a kbase for each request still adds
> unnecessary overhead to your application, and kbases are designed to be
> shared in such cases. If you need to orchestrate multiple execution paths
> for your rules, you could use rule flow or any other coordination
> mechanism.
> Finally, Rete is known by performing really well with increasing number of
> rules, since the performance is not dependent on the number of existing
> rules, but on the number of affected constraints.
>
> Just my .02c
>
> Edson
>
>
> 2009/12/22 malkhafaji <moe.alkhafaji at medcpu.com>
>
>>
>> Hello,
>>
>> I am trying to create multiple sessions, and for each session I will load
>> one knowledge package representing one drl. Each drl may optionally load
>> additional knowledge packages (drls). Since all sessions will be
>> accessing
>> the same list of knowledge packages, and since they take a long time to
>> compile resources, I decided to create a Map with all possible knowledge
>> packages that all sessions may use. That worked beautifully saving me
>> compilation time (it is done at start up).
>>
>> Now, here is how I am creating the static map:
>>
>> private static ConcurrentMap<String, KnowledgePackage> knowledgePackages
>> =
>> new
>> ConcurrentHashMap<String, KnowledgePackage>();
>>
>> Here is how I am initializing it:
>>
>> KnowledgeBuilder kbuilder = null;
>>
>> for (MedCPUKnowledgeBase medcpuKnowledgeBase :
>> medcpuKnowledgeBases) {
>> try {
>> kbuilder =
>> KnowledgeBuilderFactory.newKnowledgeBuilder();
>>
>> // This call actually compiles the drl
>> file.
>>
>>
>> kbuilder.add(ResourceFactory.newClassPathResource(medcpuKnowledgeBase.getFileName()),
>> ResourceType.DRL);
>>
>> KnowledgeBuilderErrors errors =
>> kbuilder.getErrors();
>>
>> if (errors.size() > 0) {
>> .....
>> } else {
>>
>> knowledgePackages.put(medcpuKnowledgeBase.getFileName(),
>> [the package just
>> added above]);
>> }
>> } catch(Exception ex) {
>> ....
>> } else {
>> .....
>> }
>> }
>> }
>>
>>
>> Each session will do this to get the pre-compiled KnowledgePackage:
>>
>> KnowledgePackage knowledgePackage = knowledgePackages.get(kb);
>> ......
>> Collection<KnowledgePackage> packages = new
>> ArrayList<KnowledgePackage>();
>> packages.add(knowledgePackage);
>>
>> // The problem is this guy (after a relatively small number of requests
>> each
>> opening a new session) just gets stuck!! It does not throw an exception
>> and
>> it does not return.
>> this.knowledgeBase.addKnowledgePackages(packages);
>>
>> When I did not share the KnowledgePackages like I did above, I was able
>> to
>> get thousands of requests with each having its own session,
>> knowledgebase,
>> and its own knowledge packages after they compile the respective drls.
>> However, because this was slow compiling the same drls over and over
>> again
>> I
>> switched to the design above which after only 20 or 30 requests it gets
>> stuck on the line above. I still have a knowledgebase per session per
>> request, but now I am sharing the knowledge packages.
>>
>> I cannot find anywhere where it says that KnowledgePackage objects are
>> not
>> thread-safe (not safe to be shared between sessions/threads). Any idea
>> why
>> I
>> am stuck on the line above? Thanks!
>> --
>> View this message in context:
>> http://n3.nabble.com/Sessions-Sharing-KnowledgeBase-tp96894p96894.html
>> Sent from the Drools - User mailing list archive at Nabble.com.
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>> https://lists.jboss.org/mailman/listinfo/rules-users
>>
>
>
>
> --
> Edson Tirelli
> JBoss Drools Core Development
> JBoss by Red Hat @ www.jboss.com
>
> _______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
>
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