ArrayIndexOutOfBoundsException in NearestSortingList

[oniatus]

Maybe an issue in the sort logic or an issue in the add-remove logic of the list?

What actually happened

Random Multiplayer Testing with the gci content and NeoTTA with ~6 players.

How to reproduce

I have no idea :) It occured only once so far.

Log details

Only this one, all other lines were unrelated (chat events, destroyed entities, multiple chunks loaded)
19:58:01.762 [Timer-1] ERROR o.t.r.logic.NearestSortingList - Uncaught exception in sorting thread: java.lang.ArrayIndexOutOfBoundsException: 200

[oniatus]

I changed the logging at the code location a bit. We should get a stacktrace when this hits again.

[Cervator]

Thanks! I just updated the event server to Omega 652, which includes that and some other stuff :-)

Feel free to join up to try to crash sometime: http://jenkins.terasology.org/job/DistroOmega/652/artifact/distros/omega/build/distributions/TerasologyOmega.zip

(I'll be sleeping soon but maybe more tomorrow)

[Cervator]

Is this what we're looking for? Happened while testing in single player with some, uh, creative railgun usage (drilling straight down to get to the underworld - my new PC can do this with no apparent slowdown holding down the right mouse button)

18:50:03.435 [Saving-0] INFO  o.t.p.internal.SaveTransaction - Save game finished
18:50:15.569 [Timer-0] ERROR o.t.r.logic.NearestSortingList - Uncaught exception in sorting thread
java.lang.ArrayIndexOutOfBoundsException: 2704
	at gnu.trove.impl.hash.TLongHash.index(TLongHash.java:216)
	at gnu.trove.map.hash.TLongObjectHashMap.get(TLongObjectHashMap.java:212)
	at org.terasology.entitySystem.entity.internal.ComponentTable.get(ComponentTable.java:41)
	at org.terasology.entitySystem.entity.internal.PojoEntityManager.getComponent(PojoEntityManager.java:591)
	at org.terasology.entitySystem.entity.internal.BaseEntityRef.getComponent(BaseEntityRef.java:100)
	at org.terasology.logic.location.DistanceComparator.compare(DistanceComparator.java:77)
	at org.terasology.logic.location.DistanceComparator.compare(DistanceComparator.java:32)
	at java.util.TimSort.mergeLo(TimSort.java:717)
	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 java.util.List.sort(List.java:478)
	at java.util.Collections.sort(Collections.java:175)
	at org.terasology.rendering.logic.NearestSortingList$SortTask.sort(NearestSortingList.java:450)
	at org.terasology.rendering.logic.NearestSortingList$SortTask.run(NearestSortingList.java:418)
	at java.util.TimerThread.mainLoop(Timer.java:555)
	at java.util.TimerThread.run(Timer.java:505)
18:50:15.615 [Timer-0] WARN  o.t.r.logic.NearestSortingList - The commands list was not emptied properly!

[oniatus]

Deeper than expected and a good spot for digging :)

Basic Idea of the class seems to be to clone the internal list before sorting (synchronized), then sort the list (unsynchronized) and then apply pending add/remove/clear operations to the list (synchronized).

One guess by a short look: If two threads sort the list in parallel (can this happen at all?) and there are pending add/remove commands, will the first thread apply the commands and the second one replace the updated list with the old one?

[elwe74]

I had the same exception. I have looked into the class TLongHash and found an error which may cause the exception:

In the super-constructor (TPrimitiveHash and THash) the method setUp(..) is called which is overridden in TLongHash to do some initialisation in class TLongHash.

This is not allowed: If TLongHash-constructor calls super(), no fields of TLongHash are existing yet and so cannot be correctly initialised by the setUp(..)-call in the super-constructor.

[oniatus]

Did some deeper debugging and testing, probably found the isse - at least i can't reproduce it anymore with #2884 in place. Prior to the changes i got the exception every time after excessive railgun use.