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https://issues.apache.org/jira/browse/HBASE-13408?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14999480#comment-14999480
 ] 

Hadoop QA commented on HBASE-13408:
-----------------------------------

{color:red}-1 overall{color}.  Here are the results of testing the latest 
attachment 
  
http://issues.apache.org/jira/secure/attachment/12771605/HBASE-13408-trunk-v10.patch
  against master branch at commit 1a6ec1bac65fa04a30a57891fb66dd248f3bed9c.
  ATTACHMENT ID: 12771605

    {color:green}+1 @author{color}.  The patch does not contain any @author 
tags.

    {color:green}+1 tests included{color}.  The patch appears to include 66 new 
or modified tests.

    {color:green}+1 hadoop versions{color}. The patch compiles with all 
supported hadoop versions (2.4.0 2.4.1 2.5.0 2.5.1 2.5.2 2.6.0 2.6.1 2.7.0 
2.7.1)

    {color:green}+1 javac{color}.  The applied patch does not increase the 
total number of javac compiler warnings.

    {color:green}+1 protoc{color}.  The applied patch does not increase the 
total number of protoc compiler warnings.

    {color:green}+1 javadoc{color}.  The javadoc tool did not generate any 
warning messages.

    {color:green}+1 checkstyle{color}.  The applied patch does not increase the 
total number of checkstyle errors

    {color:green}+1 findbugs{color}.  The patch does not introduce any  new 
Findbugs (version 2.0.3) warnings.

    {color:red}-1 release audit{color}.  The applied patch generated 1 release 
audit warnings (more than the master's current 0 warnings).

    {color:green}+1 lineLengths{color}.  The patch does not introduce lines 
longer than 100

  {color:green}+1 site{color}.  The mvn post-site goal succeeds with this patch.

    {color:green}+1 core tests{color}.  The patch passed unit tests in .

Test results: 
https://builds.apache.org/job/PreCommit-HBASE-Build/16482//testReport/
Release audit warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/16482//artifact/patchprocess/patchReleaseAuditWarnings.txt
Release Findbugs (version 2.0.3)        warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/16482//artifact/patchprocess/newFindbugsWarnings.html
Checkstyle Errors: 
https://builds.apache.org/job/PreCommit-HBASE-Build/16482//artifact/patchprocess/checkstyle-aggregate.html

  Console output: 
https://builds.apache.org/job/PreCommit-HBASE-Build/16482//console

This message is automatically generated.

> HBase In-Memory Memstore Compaction
> -----------------------------------
>
>                 Key: HBASE-13408
>                 URL: https://issues.apache.org/jira/browse/HBASE-13408
>             Project: HBase
>          Issue Type: New Feature
>            Reporter: Eshcar Hillel
>            Assignee: Eshcar Hillel
>             Fix For: 2.0.0
>
>         Attachments: HBASE-13408-trunk-v01.patch, 
> HBASE-13408-trunk-v02.patch, HBASE-13408-trunk-v03.patch, 
> HBASE-13408-trunk-v04.patch, HBASE-13408-trunk-v05.patch, 
> HBASE-13408-trunk-v06.patch, HBASE-13408-trunk-v07.patch, 
> HBASE-13408-trunk-v08.patch, HBASE-13408-trunk-v09.patch, 
> HBASE-13408-trunk-v10.patch, 
> HBaseIn-MemoryMemstoreCompactionDesignDocument-ver02.pdf, 
> HBaseIn-MemoryMemstoreCompactionDesignDocument-ver03.pdf, 
> HBaseIn-MemoryMemstoreCompactionDesignDocument.pdf, 
> InMemoryMemstoreCompactionEvaluationResults.pdf, 
> InMemoryMemstoreCompactionMasterEvaluationResults.pdf, 
> InMemoryMemstoreCompactionScansEvaluationResults.pdf, 
> StoreSegmentandStoreSegmentScannerClassHierarchies.pdf
>
>
> A store unit holds a column family in a region, where the memstore is its 
> in-memory component. The memstore absorbs all updates to the store; from time 
> to time these updates are flushed to a file on disk, where they are 
> compacted. Unlike disk components, the memstore is not compacted until it is 
> written to the filesystem and optionally to block-cache. This may result in 
> underutilization of the memory due to duplicate entries per row, for example, 
> when hot data is continuously updated. 
> Generally, the faster the data is accumulated in memory, more flushes are 
> triggered, the data sinks to disk more frequently, slowing down retrieval of 
> data, even if very recent.
> In high-churn workloads, compacting the memstore can help maintain the data 
> in memory, and thereby speed up data retrieval. 
> We suggest a new compacted memstore with the following principles:
> 1.    The data is kept in memory for as long as possible
> 2.    Memstore data is either compacted or in process of being compacted 
> 3.    Allow a panic mode, which may interrupt an in-progress compaction and 
> force a flush of part of the memstore.
> We suggest applying this optimization only to in-memory column families.
> A design document is attached.
> This feature was previously discussed in HBASE-5311.



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