[rules-users] GC Overhead Limit Exceeded and 1B JoinLeftNode Objects

[Julian Klein]

Ok, thanks.  Here's what I have so far:

1) I am not retracting facts or setting expiration.  This is by design
since I am doing the next item.  Do I need to retract globals?
2) I have disposed the session when I ran with a StatefulSession.  I
understood this means I do not need to retract facts.  I do not attempt to
reuse the session.  I am now trying to use a StatelessSession.
3) Unfortunately, the rule base is very large and this will take a long
time.  I am hoping to at least get to a point where this runs end-to-end.
 If it takes several hours, I am ok with that.
4) I would expect everything except "eval" statements to take advantage of
indexing in my rules.   Are you talking about BetaNode indexing?  In all
cases, I use the property access over getters.
5) Since I am using a stateless session, I would expect no recursion.
6) Got it.  Thanks.
7) Does this only apply with a shared KnowledgeBase?  What if I spawn
multiple sessions in separate threads?

All in all, I reduced the allocated heap size and ran jmap as recommended
by Wolfgang with a 6GB heap, 4 threads running sessions via a ForkJoinPool
and less than 100K facts.  Here is a snapshot of the top hits.  I ran this
multiple times, and just like JProfiler, the JoinNodeLeftTuple continue to
grow and grow.  I would expect this to fluctuate up and down in count and
size since I am not re-using a session.  Not being familiar with the
internals of Drools, I am hoping someone could provide a sense of whether
or not the below points to one of the issues Mark mentioned above.  Also,
during GC events only Eden space gets freed up so these objects appear to
be living in Tenured space.  This further concerns me that something is not
being cleaned up.

I fear it is all not so simple and will continue looking into Mark's list
for opportunities in my code base as well as work towards simple test case.
 I appreciate all the time taken to read my rather lengthy emails.  I am
hoping that this detail will help others as it has me.  Thank you.

 num     #instances         #bytes  class name
----------------------------------------------
   1:      61754567     4940365360  org.drools.reteoo.JoinNodeLeftTuple
   2:       1954644      109460064  org.drools.reteoo.RightTuple
   3:        302247       24179760  org.drools.common.AgendaItem
   4:        447814       21495072  com.mycompany.loader.FactsLoader  <- A
bunch of callable objects that get executed to load data to send to Drools
when the processor(s) is (are) idle.
   5:        302247       19343808
 org.drools.reteoo.RuleTerminalNodeLeftTuple
   6:        897091       14353456  java.lang.Integer
   7:        447814       14330048  java.util.RandomAccessSubList
   8:        300383       11743152  [C
   9:        447815       10747560
 java.util.Collections$SynchronizedRandomAccessList



On Sat, Feb 23, 2013 at 5:57 PM, Julian Klein <julianklein at gmail.com> wrote:

> This is great.  It sounds like I have to go back to the drawing board.  It
> may take a while to work through this list.  I'll circle back with outcomes.
>
> Thank you.
>
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