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From "Anoop Sam John (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-11882) Row level consistency may not be maintained with bulk load and compaction
Date Tue, 02 Sep 2014 19:51:22 GMT

    [ https://issues.apache.org/jira/browse/HBASE-11882?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14118620#comment-14118620
] 

Anoop Sam John commented on HBASE-11882:
----------------------------------------

bq.Then I think the above change is not necessary and only handle the case as per the initial
patch where we handle same KVs case
This is what your last comment in HBase-11591 regarding the read point check for bulk loaded
files.  So we were continuing with existing way(?)

I am +1 for option2
bq.Option2. Transfer the bulk load seqId into the cells during compaction.
In read we set each Cell seqId with the seqId of the file right? Compaction read cells from
store files and write to single file. So this set of seqId not happening?


> Row level consistency may not be maintained with bulk load and compaction
> -------------------------------------------------------------------------
>
>                 Key: HBASE-11882
>                 URL: https://issues.apache.org/jira/browse/HBASE-11882
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver
>    Affects Versions: 1.0.0, 2.0.0
>            Reporter: Jerry He
>            Priority: Critical
>             Fix For: 1.0.0, 2.0.0
>
>         Attachments: TestHRegionServerBulkLoad.java.patch
>
>
> While looking into the TestHRegionServerBulkLoad failure for HBASE-11772, I found the
root cause is that row level atomicity may not be maintained with bulk load together with
compation.
> TestHRegionServerBulkLoad is used to test bulk load atomicity. The test uses multiple
threads to do bulk load and scan continuously and do compactions periodically. 
> It verifies row level data is always consistent across column families.
> After HBASE-11591, we added readpoint checks for bulkloaded data using the seqId at the
time of bulk load. Now a scanner will not see the data from a bulk load if the scanner's readpoint
is earlier than the bulk load seqId.
> Previously, the atomic bulk load result is visible immediately to all scanners.
> The problem is with compaction after bulk load. Compaction does not lock the region and
it is done one store (column family) at a time. It also compact away the seqId marker of bulk
load.
> Here is an event sequence where the row level consistency is broken.
> 1. A scanner is started to scan a region with cf1 and cf2. The readpoint is 10.
> 2. There is a bulk load that loads into cf1 and cf2. The bulk load seqId is 11. Bulk
load is guarded by region write lock. So it is atomic.
> 3. There is a compaction that compacts cf1. It compacts away the seqId marker of the
bulk load.
> 4. The scanner tries to next to row-1001. It gets the bulk load data for cf1 since there
is no seqId preventing it.  It does not get the bulk load data for cf2 since the scanner's
readpoint (10) is less than the bulk load seqId (11).
> Now the row level consistency is broken in this case.



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