5:18 a.m.
Wolfgang,
thanks for the prompt reply. Inline comments.
On 25 March 2014 09:12, Wolfgang Laun <wolfgang.laun(a)gmail.com> wrote:
A rule with timer will only continue firing if its first true state
remains constant. This means that you can't do what you want to do
this way. (You might set up a rule with a repeating or cron timer that
inserts a Trigger fact that triggers the accumulate and is retracted,
or do some similar haque.)
This is exactly what we did (the "pretentiously called" pub/sub pattern).
declare CronTrigger
@role( event )
@timestamp( timestamp )
interval : String
timestamp : Date
end
declare MetricRequest
metric : String
end
declare Subscription
key : String
interval : String
end
And the rules are:
// Setup rules
rule "Create subscriptions"
when
then
insert( new Subscription("epm", "10s") );
end
// Cron management
rule "Cron trigger 10s"
timer ( cron: 0/10 * * * * ? )
when
then
entryPoints["triggers"].insert( new CronTrigger( "10s", new Date() )
);
end
rule "Subscription"
when
CronTrigger( $interval := interval ) from entry-point "triggers"
Subscription( $interval := interval, $key : key )
then
entryPoints["requests"].insert( new MetricRequest($key) );
end
// Business rules
rule "Create counter"
when
$e : SynthEvent() from entry-point "synth"
then
entryPoints["counters"].insert( new EventCounter( $e.getId(),
"event",
$e.getTimestamp() ) );
end
// Metrics
rule "Count epm"
when
$req : MetricRequest( metric == "epm" ) from entry-point "requests"
Number( $count : intValue ) from accumulate(
EventCounter( key == "event" ) over window:time( 60s ) from
entry-point "counters", count(1) )
then
logger.debug("epm = {}", $count );
retract( $req );
end
The session.execute(command) is a rather roundabout way for
inserting
facts. If you want to be fast, use session.insert(.).
Good to know. Still, the system hangs (i.e. no EventCounter event created)
no matter which method I use (session.insert(e),
session.getEntryPoint("synth").insert(e) or
session.execute(CommandFactory.newInsert(e, null, false, "synth")). I
cannot see any evidence that proves one method to be less unstable than the
others. BTW, it seemed to me that session.insert wasn't working properly
but further testing proved I was wrong.
Don't use rules for keeping track what's going on, or the
Heisenberg
effect will spoil your efforts. It's better to set up insert/retract
listeners, e.g. for maintaining counters of facts per class. This
might give you a better idea of what goes on and wrong. (We'd all be
interested to hear more about the effect you've described!)
Actually, we are working on a real-time analytic tool and, yes, the
capability to generate temporally aggregated metrics, either from original
or inferred events, is crucial for us. This synthetic example is just a
test case, and I hoped it would go more smoothly. We used ESPER here and
there, and Drools Expert in many of our projects. We would love to switch
to Drools also for the CEP part, but I must admit I am a bit worried by our
initial tests.
Hopefully, with the help of the Drools' Community we'll manage to solve our
current issues ;)
So said:
1. No matter how we add events to the session, at some point the "Create
counter" rule stops triggering and inferred events aren't created
anymore.
2. If we switch to the pub/sub the system is more stable. Still, it
hangs as we either increase the throughput or add complexity (read more
rules).
Hope we'll get some help from this valuable community.
Thanks,
Vieri
Cheers
-W
P.S. Full source code (not much more than I posted here) available on
request. Just to speed up things a bit ;)
On 25/03/2014, Vieri <vieri.emiliani(a)gmail.com> wrote:
> Dear Drools Experts,
>
>
> *Short version*
>
>
> 1. Cron-based rules triggers (more than once) for a full second,
rather
> than once every defined period;
> 2. After some time, event creation from the drl seems to hang. The
"time
> to hang" decreases as we increase the throughput of incoming events;
> 3. The two issues seem to be somehow related (well, maybe).
>
> *Full version*
>
>
> We are testing Drools Fusion to implement CEP functionalities in our
> platform. We are performing these tests using Drools 6.0.1.Final.
>...
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--
Vieri Emiliani