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From "ramkrishna.s.vasudevan (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4528) The put operation can release the rowlock before sync-ing the Hlog
Date Fri, 21 Oct 2011 08:54:32 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4528?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13132523#comment-13132523
] 

ramkrishna.s.vasudevan commented on HBASE-4528:
-----------------------------------------------

@Dhruba
I found one more thing using the testcase TestParallelPut.java.  If the LogSyncer thread starts
running first time the unflushedEntries will be 0 and syncedTillHere will also be 0.
Now first put will make this unFlushedEntries to be 1.  Now the LogSyncer thread will check
for the condition 
{code}
   try {
            if (unflushedEntries.get() <= syncedTillHere) {
              Thread.sleep(this.optionalFlushInterval);
            }
            sync();
          }
{code}
now there is a chance that just after the append is completed to HLog before the lock gets
released the entry may be synced because of LogFlusher Thread.  Is it ok ? Pls correct me
if am wrong. I think it should not be a problem but syncing will happen in 2 different places.
 
                
> The put operation can release the rowlock before sync-ing the Hlog
> ------------------------------------------------------------------
>
>                 Key: HBASE-4528
>                 URL: https://issues.apache.org/jira/browse/HBASE-4528
>             Project: HBase
>          Issue Type: Improvement
>          Components: regionserver
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>             Fix For: 0.94.0
>
>         Attachments: appendNoSync5.txt, appendNoSyncPut1.txt, appendNoSyncPut2.txt, appendNoSyncPut3.txt,
appendNoSyncPut4.txt, appendNoSyncPut5.txt, appendNoSyncPut6.txt
>
>
> This allows for better throughput when there are hot rows. A single row update improves
from 100 puts/sec/server to 5000 puts/sec/server.

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