[rules-users] Pooling KnowledgeBase instances

[travistcummings]

Hi,

I am running into an issue in a highly concurrent environment where my
threads are waiting on locking of the rule base when I try to insert into
the session.  I am wondering if an appropriate solution would be to create a
pool of KnowledgeBase objects, each having its own rule base.  A thread dump
of my server had the message below for about 40 threads.

For my use case, I create the knowledge base once, then don't modify it in
any way.

Thank you!
Travis


"ajp-bio-8010-exec-984" daemon prio=10 tid=0x081f3800 nid=0x2a7c waiting on
condition [0x9f368000]
   java.lang.Thread.State: WAITING (parking)
	at sun.misc.Unsafe.park(Native Method)
	- parking to wait for  <0xf0489a50> (a
java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync)
	at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
	at
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:834)
	at
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:867)
	at
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1197)
	at
java.util.concurrent.locks.ReentrantReadWriteLock$WriteLock.lock(ReentrantReadWriteLock.java:945)
	at
org.drools.common.UpgradableReentrantReadWriteLock.lowPriorityWriteLock(UpgradableReentrantReadWriteLock.java:105)
	at
org.drools.common.UpgradableReentrantReadWriteLock.writeLock(UpgradableReentrantReadWriteLock.java:88)
	at org.drools.common.AbstractRuleBase.lock(AbstractRuleBase.java:475)
	at
org.drools.reteoo.builder.PatternBuilder.attachObjectTypeNode(PatternBuilder.java:276)
	at
org.drools.reteoo.ClassObjectTypeConf.<init>(ClassObjectTypeConf.java:103)
	at
org.drools.common.ObjectTypeConfigurationRegistry.getObjectTypeConf(ObjectTypeConfigurationRegistry.java:71)
	at org.drools.reteoo.Rete.assertObject(Rete.java:107)
	at org.drools.reteoo.ReteooRuleBase.assertObject(ReteooRuleBase.java:286)
	at
org.drools.reteoo.ReteooWorkingMemory$WorkingMemoryReteAssertAction.execute(ReteooWorkingMemory.java:434)
	at
org.drools.common.AbstractWorkingMemory.executeQueuedActions(AbstractWorkingMemory.java:993)
	at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:335)
	at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:311)
	at
org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:903)
	at
org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:847)
	at
org.drools.impl.StatefulKnowledgeSessionImpl.insert(StatefulKnowledgeSessionImpl.java:269)



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