[rules-users] Fusion appears to be working properly, but...

[Wolfgang Laun]

On 14 October 2011 06:31, slyfox <bobby.richards at gmail.com> wrote:

> thanks for the response, that makes a little more sense.  That is an issue
> because the whole idea of CEP is to process events as they happen.  My next
> step is adding camel support so that I can consume the amqp feed without
> manually inserting into the session.  I guess fireuntilhalt is my only
> option.  But what does fire until halt do, is it just a continuous loop or
> is is smart enough to only process events when they come in?
>

There is one reasons for the thread running a Drools engine until halt
to become active: when a fact is inserted. After doing the work resulting
from this, the thread falls back into suspension.


> so what would happen if the event is given an expiration of say 2 seconds?
> if you were calling fireallrules in anything over a 2 second interval you
> would miss a lot.
>

An event that has expired any time before you fireAllRules is discarded
soon after this call is entered. What could you "miss" in the time between
the scheduled expiry and the actual removal?

Note that any application that expects to produce real-time reactions
is bound to fireUntilHalt.



> I do not really see the benefit of fusion then, seems like its redundant?
>  I
> hope that I am missing something.
>

There isn't really a "Fusion" thing. (Think of it as a marketing gag.)
The Drools Rule Engine is capable of dealing with facts that have the
distinct traits of what is called "event": timestamp, duration and
expiry; the Engine is clever enough to retract stale events automatically,
and there's a set of operators for comparing numbers that may
represent points in time with some fancy overlap options. If you don't
need anything of this, don't use it; OTOH, if you compare dates, just
using the temporal operators may help.

-W

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