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https://issues.apache.org/jira/browse/HBASE-6195?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13292625#comment-13292625
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Xing Shi commented on HBASE-6195:
---------------------------------
Here is the data:
I delete the row first, and then use 2000 threads to increment one row, each
increment 1000, after all threads done, I read the increment row's value, do 11
times.
for i in `seq 0 10`
do
/home/shubao.sx/hadoop-0.20.2-cdh3u3/bin/hadoop --config
/home/shubao.sx/0.90-hadoop-config jar /home/shubao.sx/inc-no-delete/inc.jar
com.taobao.hbase.MultiThreadsIncrement --threadNum 2000 --inc 1000
>/home/shubao.sx/inc-no-delete/inc.$i.log
done
and the results:
inc.0.log : return 199838
inc.1.log : return 399729
inc.2.log : return 599579
inc.3.log : return 799441
inc.4.log : return 999305
inc.5.log : return 1199173
inc.6.log : return 1399037
inc.7.log : return 1598939
inc.8.log : return 1798804
inc.9.log : return 1998708
inc.10.log : return 2198637
Because I set the hlog's parameter
<property>
<name>hbase.regionserver.logroll.multiplier</name>
<value>0.005</value>
</property>
<property>
<name>hbase.regionserver.maxlogs</name>
<value>3</value>
</property>
so the memstore flush occurs often.
> Increment data will lost when the memstore flushed
> --------------------------------------------------
>
> Key: HBASE-6195
> URL: https://issues.apache.org/jira/browse/HBASE-6195
> Project: HBase
> Issue Type: Bug
> Components: regionserver
> Reporter: Xing Shi
>
> There are two problems in increment() now:
> First:
> I see that the timestamp(the variable now) in HRegion's Increment() is
> generated before got the rowLock, so when there are multi-thread increment
> the same row, although it generate earlier, it may got the lock later.
> Because increment just store one version, so till now, the result will still
> be right.
> When the region is flushing, these increment will read the kv from snapshot
> and memstore with whose timestamp is larger, and write it back to memstore.
> If the snapshot's timestamp larger than the memstore, the increment will got
> the old data and then do the increment, it's wrong.
> Secondly:
> Also there is a risk in increment. Because it writes the memstore first and
> then HLog, so if it writes HLog failed, the client will also read the
> incremented value.
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