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https://issues.apache.org/jira/browse/GEODE-2240?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15767845#comment-15767845
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Darrel Schneider commented on GEODE-2240:
-----------------------------------------
I think this bug might be caused by the code that adds to "expiredTombstones",
TombstoneService.ReplicateTombstoneSweeper.expireTombstone, not syncing on
getBlockGCLock() as the code that removes from "expiredTomstones",
TombstoneService.ReplicateTombstoneSweeper.removeExpiredIf, does.
Since these are the only two methods that modify the "expiredTombstones"
collection they need a common sync to prevent unsafe concurrent modification of
the ArrayList.
I think the only time multiple threads would do this concurrently is when a
region is being destroyed.
> unexpected NullPointerException from Tombstone service
> ------------------------------------------------------
>
> Key: GEODE-2240
> URL: https://issues.apache.org/jira/browse/GEODE-2240
> Project: Geode
> Issue Type: Bug
> Components: regions
> Reporter: Darrel Schneider
>
> A test failed and the logs were found to be full of NPEs from the tombstone
> service:[severe 2016/12/20 02:04:35.605 UTC
> dataStoregemfire7_rs-StorageBTTest-2016-12-19-23-35-42-client-14_19508
> <Replicate/Partition Region Garbage Collector> tid=0x44] GemFire garbage
> collection service encountered an unexpected exception
> java.lang.NullPointerException
> at
> org.apache.geode.internal.cache.TombstoneService$TombstoneSweeper.lambda$purgeObsoleteTombstones$1(TombstoneService.java:938)
> at
> org.apache.geode.internal.cache.TombstoneService$ReplicateTombstoneSweeper.removeExpiredIf(TombstoneService.java:479)
> at
> org.apache.geode.internal.cache.TombstoneService$TombstoneSweeper.removeIf(TombstoneService.java:823)
> at
> org.apache.geode.internal.cache.TombstoneService$TombstoneSweeper.purgeObsoleteTombstones(TombstoneService.java:937)
> at
> org.apache.geode.internal.cache.TombstoneService$TombstoneSweeper.run(TombstoneService.java:880)
> at java.lang.Thread.run(Thread.java:745)
> [severe 2016/12/20 02:05:45.987 UTC
> dataStoregemfire7_rs-StorageBTTest-2016-12-19-23-35-42-client-14_19508
> <Replicate/Partition Region Garbage Collector> tid=0x44] GemFire garbage
> collection service encountered an unexpected exception
> java.lang.NullPointerException
> at
> org.apache.geode.internal.cache.TombstoneService$ReplicateTombstoneSweeper.expireBatch(TombstoneService.java:524)
> at
> org.apache.geode.internal.cache.TombstoneService$ReplicateTombstoneSweeper.checkExpiredTombstoneGC(TombstoneService.java:594)
> at
> org.apache.geode.internal.cache.TombstoneService$TombstoneSweeper.run(TombstoneService.java:878)
> at java.lang.Thread.run(Thread.java:745)
> Both of these stacks indicate that the "expiredTombstones" ArrayList somehow
> has nulls in it. It is an ArrayList of Tombstone instances and the only code
> that adds to it first tests that the item it is adding is not null. The only
> other modify operation done on it is to remove an item.
> Perhaps unsafe concurrent access is happening causing this code to see nulls.
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