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Date: Sat, 15 Sep 2007 13:24:32 -0700 (PDT)
From: "Hadoop QA (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Commented: (HADOOP-1903) [hbase] Possible data loss if
 Exception happens between snapshot and flush to disk.
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    [ https://issues.apache.org/jira/browse/HADOOP-1903?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12527778 ] 

Hadoop QA commented on HADOOP-1903:
-----------------------------------

+1 overall.  Here are the results of testing the latest attachment 
http://issues.apache.org/jira/secure/attachment/12365914/1903.patch
against trunk revision r575950.

    @author +1.  The patch does not contain any @author tags.

    javadoc +1.  The javadoc tool did not generate any warning messages.

    javac +1.  The applied patch does not generate any new compiler warnings.

    findbugs +1.  The patch does not introduce any new Findbugs warnings.

    core tests +1.  The patch passed core unit tests.

    contrib tests +1.  The patch passed contrib unit tests.

Test results: http://lucene.zones.apache.org:8080/hudson/job/Hadoop-Patch/772/testReport/
Findbugs warnings: http://lucene.zones.apache.org:8080/hudson/job/Hadoop-Patch/772/artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html
Checkstyle results: http://lucene.zones.apache.org:8080/hudson/job/Hadoop-Patch/772/artifact/trunk/build/test/checkstyle-errors.html
Console output: http://lucene.zones.apache.org:8080/hudson/job/Hadoop-Patch/772/console

This message is automatically generated.

> [hbase] Possible data loss if Exception happens between snapshot and flush to disk.
> -----------------------------------------------------------------------------------
>
>                 Key: HADOOP-1903
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1903
>             Project: Hadoop
>          Issue Type: Bug
>            Reporter: stack
>            Assignee: stack
>            Priority: Minor
>             Fix For: 0.15.0
>
>         Attachments: 1903.patch
>
>
> There exists a little window during which we can lose data.  During a memcache flush, we make an inmemory copy, a 'snapshot'.  The memcache is then zeroed and off we go again taking updates.  Meantime, in background we are supposed to flush the snapshot to disk.  If this process is interrupted -- e.g. the HDFS is yanked from under us or if an OOME occurs in this thread -- then the content of the snapshot is lost.

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