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https://issues.apache.org/jira/browse/HBASE-15959?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15319926#comment-15319926
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Appy commented on HBASE-15959:
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bq. region.compact doesn't compact mob files, I think this is not related with
cleaners.
If it's moving cells from mob to store, doesn't that mean it's compacting mob
files too.
[Here|https://github.com/apache/hbase/blob/7efb9edecbdf8b35046230575d504e4caeb80f34/hbase-server/src/main/java/org/apache/hadoop/hbase/mob/DefaultMobStoreCompactor.java#L213],
we are moving mob cells to store or new writer.
You're right, first two parts are very clear what they are doing. Set the
thresholds, expect things to move around.
bq. In the 2nd compaction, the threshold is changed to 0, and all cells are
moved to mob files from store files. And in the second scan, the cells are the
reference ones.
Cells 0-4 got moved to store file in the first compaction. And that's why in
the [second
scan|https://github.com/apache/hbase/blob/master/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestRegionServerMetrics.java#L441],
there is [no mob
cell|https://github.com/apache/hbase/blob/master/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestRegionServerMetrics.java#L445].
And we write cells 5-9 before [threshold is ste to
0|https://github.com/apache/hbase/blob/master/hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestRegionServerMetrics.java#L453],
so they should be non-mob cells too.
So when the second compaction kicks, I would expect them to be non-reference
cells. It's only after the compaction has finished, that they'll become the
reference cells again.
(Just to be sure, reference cells = mob cells, right?)
> 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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