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https://issues.apache.org/jira/browse/HBASE-15959?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15319858#comment-15319858
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huaxiang sun commented on HBASE-15959:
--------------------------------------
I have a patch ready. The root cause is
{code}
assertCounter("cellsCountCompactedToMob", 2 * numHfiles);
{code}
Assumes that there is no mob reference cells. Actually, after the first major
compact, the compacted files are still there in the family directory
(compaction.discharger does not get chance to kick in yet). When scan for the
next major compaction, these files may still be used, so scan may hit the cells
in these compacted files (hence it has mob reference).
The fix is to wait compaction.discharger to move compacted files to archive and
then start the second major compaction.
I will upload a patch after some clean up.
> Fix flaky test TestRegionServerMetrics.testMobMetrics
> -----------------------------------------------------
>
> Key: HBASE-15959
> URL: https://issues.apache.org/jira/browse/HBASE-15959
> Project: HBase
> Issue Type: Bug
> Reporter: Appy
> Assignee: huaxiang sun
>
> It flakes
> [here|https://github.com/apache/hbase/blob/b557f0bec62a48753e5d01d7a47f3c9e5a6b3ee8/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestRegionServerMetrics.java#L460].
> There are two weird things i identified:
> 1. In second compaction,
> [scanner|https://github.com/apache/hbase/blob/b557f0bec62a48753e5d01d7a47f3c9e5a6b3ee8/hbase-server/src/main/java/org/apache/hadoop/hbase/mob/DefaultMobStoreCompactor.java#L173]
> has 10 storefiles. Shouldn't there be 6? 5 from recent flushes and 1 from
> earlier compaction. Probably because mob cleaner doesn't clean old hfiles.
> Does this needs fixing?
> 2. Across runs, same cell (ie. same key) may or may not be considered mob
> reference cell.
> [here|https://github.com/apache/hbase/blob/b557f0bec62a48753e5d01d7a47f3c9e5a6b3ee8/hbase-server/src/main/java/org/apache/hadoop/hbase/mob/DefaultMobStoreCompactor.java#L213].
> This at least happens with row keys 0 - 4 (which got compacted earlier).
> [~jmhsieh] Any ideas why this would happen.
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