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https://issues.apache.org/jira/browse/OAK-1817?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14004556#comment-14004556
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Jukka Zitting commented on OAK-1817:
------------------------------------
It looks like the bug here is in the way the SegmentWriter keeps recently
flushed segments cached in memory. In some cases those segments are cached
using the full 256kB byte buffer even if the segment size is slightly smaller
than that. In those cases the segment still works correctly for normal access,
but the blobref entries are not accessible, which I believe is causing the NPE
here.
> NPE in MarkSweepGarbageCollector.saveBatchToFile during Datastore GC with
> FileDataStore
> ---------------------------------------------------------------------------------------
>
> Key: OAK-1817
> URL: https://issues.apache.org/jira/browse/OAK-1817
> Project: Jackrabbit Oak
> Issue Type: Bug
> Components: blob
> Affects Versions: 0.20
> Reporter: Konrad Windszus
> Assignee: Chetan Mehrotra
> Attachments: NodeAndDataStoreOsgiConfig.zip, OAK-1817.patch
>
>
> During running a datastore garbage collection on a Jackrabbit 2 FileDataStore
> (org.apache.jackrabbit.oak.plugins.blob.datastore.FileDataStore, see
> http://jackrabbit.apache.org/oak/docs/osgi_config.html) an NPE is thrown
> {code}
> 13.05.2014 17:50:16.944 *ERROR* [qtp1416657193-147]
> org.apache.jackrabbit.oak.management.ManagementOperation Blob garbage
> collection failed
> java.lang.RuntimeException: Error in retrieving references
> at
> org.apache.jackrabbit.oak.plugins.blob.MarkSweepGarbageCollector$1.addReference(MarkSweepGarbageCollector.java:395)
> at
> org.apache.jackrabbit.oak.plugins.segment.Segment.collectBlobReferences(Segment.java:248)
> at
> org.apache.jackrabbit.oak.plugins.segment.SegmentTracker.collectBlobReferences(SegmentTracker.java:178)
> at
> org.apache.jackrabbit.oak.plugins.segment.SegmentBlobReferenceRetriever.collectReferences(SegmentBlobReferenceRetriever.java:38)
> at
> org.apache.jackrabbit.oak.plugins.blob.MarkSweepGarbageCollector.iterateNodeTree(MarkSweepGarbageCollector.java:361)
> at
> org.apache.jackrabbit.oak.plugins.blob.MarkSweepGarbageCollector.mark(MarkSweepGarbageCollector.java:201)
> at
> org.apache.jackrabbit.oak.plugins.blob.MarkSweepGarbageCollector.markAndSweep(MarkSweepGarbageCollector.java:173)
> at
> org.apache.jackrabbit.oak.plugins.blob.MarkSweepGarbageCollector.collectGarbage(MarkSweepGarbageCollector.java:149)
> at
> org.apache.jackrabbit.oak.plugins.segment.SegmentNodeStoreService$2.collectGarbage(SegmentNodeStoreService.java:185)
> at org.apache.jackrabbit.oak.plugins.blob.BlobGC$1.call(BlobGC.java:68)
> at org.apache.jackrabbit.oak.plugins.blob.BlobGC$1.call(BlobGC.java:64)
> at java.util.concurrent.FutureTask.run(FutureTask.java:262)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
> at java.lang.Thread.run(Thread.java:745)
> Caused by: java.lang.NullPointerException: null
> at
> com.google.common.base.Preconditions.checkNotNull(Preconditions.java:192)
> at com.google.common.base.Joiner.toString(Joiner.java:436)
> at com.google.common.base.Joiner.appendTo(Joiner.java:108)
> at com.google.common.base.Joiner.appendTo(Joiner.java:152)
> at com.google.common.base.Joiner.join(Joiner.java:193)
> at com.google.common.base.Joiner.join(Joiner.java:183)
> at
> org.apache.jackrabbit.oak.plugins.blob.MarkSweepGarbageCollector.saveBatchToFile(MarkSweepGarbageCollector.java:317)
> at
> org.apache.jackrabbit.oak.plugins.blob.MarkSweepGarbageCollector$1.addReference(MarkSweepGarbageCollector.java:391)
> ... 14 common frames omitted
> {code}
> Attached you find the OSGi config for both the nodestore and the datastore.
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