[jboss-jira] [JBoss JIRA] (DROOLS-2346) ProtobufOutputMarshaller.orderFacts causes a "Comparison method violates its general contract" error

[Mario Fusco (JIRA)]

     [ https://issues.jboss.org/browse/DROOLS-2346?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Mario Fusco updated DROOLS-2346:
--------------------------------
    Sprint: 2018 Week 07-08


> ProtobufOutputMarshaller.orderFacts causes a "Comparison method violates its general contract" error
> ----------------------------------------------------------------------------------------------------
>
>                 Key: DROOLS-2346
>                 URL: https://issues.jboss.org/browse/DROOLS-2346
>             Project: Drools
>          Issue Type: Bug
>          Components: core engine
>    Affects Versions: 7.6.0.Final
>            Reporter: Martin Weiler
>            Assignee: Mario Fusco
>
> When marshalling kieSession in production (long running kieSession with a lot of fact insertion), we encountered the following error : 
> {noformat}
> java.lang.IllegalArgumentException: Comparison method violates its general contract!
> 	at java.util.TimSort.mergeLo(TimSort.java:777)
> 	at java.util.TimSort.mergeAt(TimSort.java:514)
> 	at java.util.TimSort.mergeCollapse(TimSort.java:439)
> 	at java.util.TimSort.sort(TimSort.java:245)
> 	at java.util.Arrays.sort(Arrays.java:1438)
> 	at org.drools.core.marshalling.impl.ProtobufOutputMarshaller.orderFacts(ProtobufOutputMarshaller.java:776)
> 	at org.drools.core.marshalling.impl.ProtobufOutputMarshaller.writeFactHandles(ProtobufOutputMarshaller.java:707)
> 	at org.drools.core.marshalling.impl.ProtobufOutputMarshaller.serializeSession(ProtobufOutputMarshaller.java:176)
> 	at org.drools.core.marshalling.impl.ProtobufOutputMarshaller.writeSession(ProtobufOutputMarshaller.java:120)
> 	at org.drools.core.marshalling.impl.ProtobufMarshaller.marshall(ProtobufMarshaller.java:164)
> 	at org.drools.core.marshalling.impl.ProtobufMarshaller.marshall(ProtobufMarshaller.java:148)
> {noformat}
> Indeed, the orderFacts method in ProtobufoutputMarshaller uses a HandleSorter as comparator, which returns the result of  o1.getId() - o2.getId()  where o1 and o2 are InternalFactHandle.
> Since the id of InternalFactHandle is an int, this comparator can cause "Comparison method violates its general contract!" IllegalArgumentException because Integer.MAX_INT + 1 < 0.
> The comparator should return the result of Integer.compare(o1.getId(), o2.getId())
> The root cause is that InternalFactHandle.getId() is an int and should be a long for long running kieSession.
> This id is generated by the FactHandleFactory (in AbstractFactHandleFactory) and is an AtomicInteger incremented at each fact creation.
> With long running kieSession a lot of fact handles can be created (inserted in memory or with "from") so this id can overflow Integer.MAX_INT and become negative, causing this issue when ordering.



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