[rules-users] Drools fusion memory management

[Edson Tirelli]

   Chris,

   I am glad you asked these questions, because I am looking for feedback on
the approaches we are using.

   So, first thing to understand is: sliding windows AND memory management
are only active when the processing mode is set to STREAM. There is no
memory management or support to sliding windows in CLOUD mode as this would
not make sense.

   Assuming the engine is set to STREAM mode, it will use 2 sources of
information to calculate the expiration time for each event type: the
@expiration policy and temporal constraints. @expiration is explicit and
obvious. For temporal constraints, the calculation is quite complex, so let
me show the simplest possible example: imagine a rule:

when
   $a : A()
   $b : B( this after[1s,30s] $a )
then
end

    In the above example, it is obvious that any A() must wait at least 30s
for eventual B()s. B()s on the other hand will either match immediately or
will never match. So, the expiration offset for A will be 30s and for B will
be 0 (zero). Now the engine will calculate the offset based on all temporal
constraints from all rules and (simplistically speaking) take the max
between the value calculated and the @expiration policy if it exists as long
as the max is not infinite. Any object type for which there are no explicit
expiration policy, nor temporal constraints from which to derive the
expiration offset will have an infinite expiration offset, i.e., will never
be automatically retracted.

   So, length sliding windows, that was what you asked about, as it is
today, will not hold the object beyond its expiration offset. Maybe we
should, maybe not... I am open to arguments on that field.

    Feedback and arguments welcome.

    []s
    Edson



2009/6/12 Chris Richmond <crichmond at referentia.com>

>  Hello,
>
>
>
> I wanted to ask this question in a separate email so as to keep each email
> to one topic for easier thread following.  Let me know if you prefer
> multiple questions per email next time.
>
>
>
>
> I am using Drools fusion basically with some success where I am at this
> point only running some aggregates and calling some java functions when a
> running average over the last 1 minute or so drops below a certain value.
>
>
>
> The sources for those values come from objects I am injecting into memory
> space, but I am not specifically calling retraction code since it is my
> understanding that I can set the policy in the rule file for how long to
> hold objects in memory.  So for example I have this rule which simpoly
> outputs to out when the average goes above 100 for the last 10 items(you can
> tell I created mine based on the stock ticker).  It seems to be working, but
> I have some questions to ensure I understand before moving forward.
>
>
>
>
>
> So below the “declare MyObject” with assigning it role event with a default
> expiration of 2 minutes.  Is my undertanding correct that fusion will
> disregard thos objects that are injected without me having to take any other
> action?
>
>
>
> Also, in my “show averages” rule below, if I did ont have the “declare
> MyObject” delcaration with expiration policy set, would fusion automatially
> throw away MyObjects older than the last 10  based on my rule no longer
> needing them?    If it would, then which takes priority, the expires
> declaration for MyObject or the no longer needed by my aggregate rule below.
>  I am assuming that the rule would keep them beyond 2 minutes it it was
> necessary, but is this correct?  If the rule as written would not
> automatically remove objects from memory space, then is there something I
> could do to tell the rule to do so when it is no longer needed by my
> aggregate?
>
>
>
> Thanks,
>
>
> Chris
>
>
>
>
>
>
>
>
>
>
>
>
>
> <imports removed>
>
>
>
>
>
> # default dialect for the semantic code will be MVEL
>
> dialect "mvel"
>
>
>
> # tells the engine that a object instance will assume the
>
> # role (semantics) of events and that the default retention
>
> # policy will be 2 minutes
>
> declare MyObject
>
>     @role( event )
>
>     @expires( 2m )
>
> end
>
>
>
>
>
> rule "show averages"
>
> when
>
>
>
>       $n : Number( doubleValue > 100 ) from accumulate (
>
>
>
>
>
>
>
>             $stat:MyObject($bc: byteCount, srcIPAddress == "10.5.0.4") over
> window:length(10) from entry-point "MyObject stream",
>
>
>
>             average( $bc )
>
>
>
>         )
>
>
>
>
>
> then
>
>
>
>     System.err.println("average: " + $n)
>
> end
>
> _______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
>


-- 
 Edson Tirelli
 JBoss Drools Core Development
 JBoss, a division of Red Hat @ www.jboss.com
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