9:19 p.m.
Thanks Thomas, Wolfgang for the inputs!
Regards,Neel
--- On Tue, 2/8/11, Wolfgang Laun <wolfgang.laun(a)gmail.com> wrote:
From: Wolfgang Laun <wolfgang.laun(a)gmail.com>
Subject: Re: [rules-users] running multiple instance of rule engine
To: "Rules Users List" <rules-users(a)lists.jboss.org>
Date: Tuesday, 2 August, 2011, 5:13 PM
2011/8/2 Neelesh Deo Dani <neeleshdev(a)yahoo.co.in>
It can be done in single session, if I make sure all the related events always go to a
particular host by partitioning input event stream.
This is an option.
Basically, I'm looking for options in a scenario when the number of input events per
sec is very large and a single instance/ host won't be able to handle the events. In
this case, we need to run multiple instance of rule engine to get the scale.
I doubt that you can do that the way you have indicated, i.e., by fetching previous events
from some store. But you might consider letting other hosts do the consequences, or even
not using a RBS at all, if the rule(s) for dealing with these input events are simple
enough.
-W
Thanks,
Neel
--- On Tue, 2/8/11, Wolfgang Laun <wolfgang.laun(a)gmail.com> wrote:
From: Wolfgang Laun <wolfgang.laun(a)gmail.com>
Subject: Re: [rules-users] running multiple instance of rule engine
To: "Rules Users List" <rules-users(a)lists.jboss.org>
Date: Tuesday, 2 August, 2011, 4:11 PM
Why
don't you do it in a single session?
The overhead created by the procedure you describe is considerable.
And you may run into synchronisation problems such as that the first event has gone to
host A, the second one goes to host B, but A hasn't stored the event yet...
-W
2011/8/2 Neelesh Deo Dani <neeleshdev(a)yahoo.co.in>
Following example clarifies the question:I've Event declaration and rule as follows:
declare Event
@role(event)
@timestamp(datetime)
datetime : Date
name : String
end
rule "Contest"
no-loop
when
$e1 : Event(name == "event1")
$e2 : Event(name == "event2", this after $e1)
then
System.out.println("rule Contest fired");
end
If Event with name "event1" is inserted in the session and after that Event with
name "event2" is inserted in the same session, then the temporal operator
("this after $e1" ) will work fine. But, if these two events are inserted in two
different sessions ( rule engine running on different host), then it won't work.
I'm trying to find a solution for this scenario. One way is to persist the events as
well in datastore and whenever any event comes, insert all the previous events also in the
session (by fetching from datastore). In this example, when event2 comes (to host2), fetch
event1 from datastore and insert it in the session so that temporal operator will work.
Is there any better alternative exists for this scenario?
Thanks,Neel
--- On Tue, 2/8/11, Abhay B. Chaware <Abhay.Chaware(a)kpitcummins.com> wrote:
What do you expect to happen in the scenario mentioned, assuming you are running
only 1 rules session? Whatever you expect to happen in this case ( e.g. latest update
wins ), you will need to implement in your persistence logic If you are using separate
rule engines/instances.
by the way, have you looked at drools grid ? I haven’t used it, but appears
to solve a similar problem that you are trying to – distributed computing.
-abhay
From: rules-users-bounces(a)lists.jboss.org
[mailto:rules-users-bounces@lists.jboss.org] On Behalf Of
Swindells, Thomas
Sent: Tuesday, August 02, 2011 1:47 PM
To: Rules Users List
Subject: Re: [rules-users] running multiple instance of rule engine
I’m not sure I understand the question.
You have two totally independent rule engine on two different servers running with
separate JVMs and sessions.
You happen to share data between the two sessions by updating a database but drools has no
knowledge of that (they are just java
objects which happen to exist) and they certainly aren’t the same object on both servers.
Temporal reasoning and correlation of events will therefore only happen on the facts that
are inserted into that processes working
memory – there’s no way it could be any way else as it only know about itself, there
could be 10 or 0 other processes running it won’t know the difference.
The ideal method is to have an application design where each request is totally
independent from all other requests (other than
db state) and therefore you do exactly as you have described – there is no other state to
share. If you have to share state between them you have a much bigger problem and you
probably have to find some other way to partition up the data into separate blocks.
Thomas
From: rules-users-bounces(a)lists.jboss.org
[mailto:rules-users-bounces@lists.jboss.org] On Behalf Of
Neelesh Deo Dani
Sent: 02 August 2011 07:42
To: rules-users(a)lists.jboss.org
Subject: [rules-users] running multiple instance of rule engine
Hi,
I need a setup where multiple instance of drools rule engine will be running in different
physical hosts. In each host, a web server (API) will be running which will receive an
input event, process it and insert into rule engine (session) for rules execution
on the same host. I'm using external persistent datastore. The objects will be
populated from datastore before inserting into the session. After rule execution if there
is any change in the state of the objects the same will be stored back to the datastore.
The datastore calls are made outside the rule execution.
In this scenario, if an event comes to one host and another event comes to a different
host, how will the temporal reasoning or correlation of events work? What is the
recommended way of deploying multiple instance of rule engine for scalability?
Please help in this regard.
Thanks & Regards,
Neel
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