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<div class="moz-cite-prefix">Could you please try version 5.6.CR1 ?
It's not available for download on the main<br>
web site, but maven will be able to retrieve it.<br>
It has many fixes, including some multi threading issues. If you
still experience the problem, <br>
we'll try and find a way to fix it in 5.6.Final, or test it with
6.x<br>
Thanks<br>
Davide<br>
<br>
On 12/12/2013 07:34 AM, Anders Henriksson wrote:<br>
</div>
<blockquote
cite="mid:c62de3125b1742cc828256c7e94e76e5@DB4PR06MB174.eurprd06.prod.outlook.com"
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<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">Hi!</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"><br>
</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">We're running drools in a multi-server
setup, with a pretty basic scenario:</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"><br>
</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">1. When the first session is needed, we
load the rulebase once. The rulebase is never changed after
this (no rule removal or addition).</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">2. Each call spawns a new
StatefulKnowledgeSession which is used for firing the rules
once and then disposed. These calls are heavily
multi-threaded, but each session is only used in a single
method call from a single thread.</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">3. We use the resource scanner to check for
updated packages. When an updated knowledge package is
available, the knowledgebase is discarded and a new one
constructed from the updated package.</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"><br>
</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">The knowledge package affected is somewhat
large - about 25 MB in size. (There are other, smaller
knowledge packages which do not appear to have this issue.)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"><br>
</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"><br>
</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">This setup has been working fine, but
somewhat slow. After upgrading to 5.5.0.Final and adding some
speedups in the surrounding code we get a spurious null
pointer. The trail of events is:</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"><br>
</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">1. After start all servers work fine.</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">2. Sometime after a couple of hours to a
couple of days, the null pointer error occurs on one or more
servers (but generally not all of them).</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">3. Once the null pointer occurs, it happens
on all further calls using that knowledgebase. No other
knowledgebases are effected. (You can load the same package in
a new knowledgebase, and sessions using the new, identical,
knowledgebase work just fine.)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">4. Restarting the java process makes the
server work fine again.</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"><br>
</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"><br>
</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">Calls always fail with the same stack
trace:</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"><br>
</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">org.drools.RuntimeDroolsException:
Unexpected exception executing action
org.drools.reteoo.ReteooWorkingMemory$WorkingMemoryReteAssertAction@5db53f</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">24</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.common.AbstractWorkingMemory.executeQueuedActions(AbstractWorkingMemory.java:995)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:335)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:311)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:903)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:847)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.impl.StatefulKnowledgeSessionImpl.insert(StatefulKnowledgeSessionImpl.java:269)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> <stacktrace from our calling code
omitted></div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">Caused by: java.lang.NullPointerException</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.rule.EvalCondition.createContext(EvalCondition.java:107)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.reteoo.EvalConditionNode.createMemory(EvalConditionNode.java:261)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.common.ConcurrentNodeMemories.createNodeMemory(ConcurrentNodeMemories.java:90)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.common.ConcurrentNodeMemories.getNodeMemory(ConcurrentNodeMemories.java:69)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.common.AbstractWorkingMemory.getNodeMemory(AbstractWorkingMemory.java:1034)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.reteoo.EvalConditionNode.assertLeftTuple(EvalConditionNode.java:174)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:196)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.reteoo.SingleLeftTupleSinkAdapter.createAndPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:145)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.reteoo.LeftInputAdapterNode.assertObject(LeftInputAdapterNode.java:154)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.reteoo.SingleObjectSinkAdapter.propagateAssertObject(SingleObjectSinkAdapter.java:59)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:235)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.reteoo.EntryPointNode.assertObject(EntryPointNode.java:240)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.reteoo.Rete.assertObject(Rete.java:109)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.reteoo.ReteooRuleBase.assertObject(ReteooRuleBase.java:286)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.reteoo.ReteooWorkingMemory$WorkingMemoryReteAssertAction.execute(ReteooWorkingMemory.java:434)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> at
org.drools.common.AbstractWorkingMemory.executeQueuedActions(AbstractWorkingMemory.java:993)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> ... 93 more</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"><br>
</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">Unfortunately we don't have the remaining
rows in the wrapped exception.</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"><br>
</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"><br>
</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">From this trace, it looks like the problem
is in EvalCondition:</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"><br>
</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> public Object createContext() {</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> return
this.expression.createContext();</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> }</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"><br>
</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">which should only be able to produce a null
pointer if expression is missing. Looking at the constructors
for this class, having a null expression seems like a valid
use case - but if this is a valid use case, why doesn't
createContext() handle this case?</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"><br>
</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">Considering that running drools with the
same package and the same inputs can either fail with the
above error (if knowledgebase has been used enough) or work
just as intended (using a newly minted knowledgebase), it
feels like something is corrupting the knowledgebase. Does
this make sense?</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"><br>
</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">(I noticed in the issue tracker (
<a class="moz-txt-link-freetext" href="https://issues.jboss.org/browse/DROOLS-156">https://issues.jboss.org/browse/DROOLS-156</a> ) that memory for
eval nodes are 'created "too lazily"' - might this be a
related issue?)</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"><br>
</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px">Best regards,</div>
<div name="divtagdefaultwrapper" id="divtagdefaultwrapper"
style="margin:0px"> Anders</div>
</div>
<br>
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</blockquote>
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