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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-663) Incorrect sequence number for cache flush
Date Thu, 05 Jun 2008 20:29:45 GMT

    [ https://issues.apache.org/jira/browse/HBASE-663?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12602770#action_12602770

stack commented on HBASE-663:

Branch does not have this issue.  Setting of sequenceid is done w/i the write lock.  No need
of backport.

> Incorrect sequence number for cache flush
> -----------------------------------------
>                 Key: HBASE-663
>                 URL: https://issues.apache.org/jira/browse/HBASE-663
>             Project: Hadoop HBase
>          Issue Type: Bug
>          Components: regionserver
>    Affects Versions: 0.1.2, 0.2.0
>            Reporter: Ning Li
>            Assignee: Jim Kellerman
>            Priority: Blocker
>             Fix For: 0.1.3, 0.2.0
> An HRegion asks each HStore to flush its cache with a sequence number X. The assumption
is that all the updates before X will be flushed. So during the startup reconstruction, the
updates before X are skipped.
> The use of updatesLock should guarantee that all the updates before X will be flushed
when HStore flushes with X - snapshots are taken after the write lock on updatesLock is acquired,
while all the updates are written to the log and to the cache with the read lock on updatesLock
is acquired. However, because the sequence number X is obtained without the write lock on
updatesLock, some updates with sequence number <= X may not have been written to the cache
which will be flushed.

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