Hi!
Just the answer I was hoping for, thanks for the fast reply!
/Mikael
Mark Proctor wrote:
Mikael Larsson wrote:
Hi!
I have some questions about multithreaded apps and if it is necessary
to pool session objects for performance.
You don't need to pool session in drools, just cache the rulebase in a
singleton.
* I understand that it is expensive to create the RuleBase objects
but what about the sessions?
If I create a new stateful session object for each request will that
become a potential bottleneck?
sessions are lightweight, do not pool.
* Is the session class thread safe, what will happen if two or more
threads simultaneously call fireAllRules on one and the same session
object?
sessions are thread safe, apart from the iterators.
One advantage of pooling session is if you have some data that does
not change per request. Say that I have some data associated with a
specific type of request that should be inserted for all requests of
that particular type and evaluated towards request specific stuff,
e.g. params in the request. E.g. An object that specifies allowed
values for a particular API will be the same for all requests (well
at least until you reconfigure the allowed values...) and the rules
would evaluate the request specific value based on the "allowed
values" object. In this case only the request specific
parameter/value needs to be inserted/retracted per request.
* I would rather use StatefulSession instead of stateless since I
find the API more flexible, are there any performance considerations
I should be aware of? If pooling is necessary I guess I must use the
stateful session. But if creating one session per request, are there
any concrete reasons for using the stateless session (besides the
simpler API and that I need to call dispose on the stateful session)?
stateless just wraps stateful anyway, stateless is really just a
convienience api - how stateless sessions do allow for "sequential
rete" which is a performance improvement if you don't need information
(fact modications leading to rule re-evaluation) but you have to go to
large number of rules and objects to see a big difference with
sequential rete.
Kind of hoping that the answer will be: "No, pooling will not be
necessary.", but any feedback about situations where it may be
necessary for best performance would be much appreciated.
No, pooling will not be neceesary.
Regards,
/Mikael
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Mikael Larsson
Redpill AB
Tel. + 46 54 15 09 40
Mob. + 46 73 42 41 483
www.redpill.se
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