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https://issues.apache.org/jira/browse/YARN-3448?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14498480#comment-14498480
 ] 

Hadoop QA commented on YARN-3448:
---------------------------------

{color:red}-1 overall{color}.  Here are the results of testing the latest 
attachment 
  http://issues.apache.org/jira/secure/attachment/12725932/YARN-3448.10.patch
  against trunk revision 1fa8075.

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

    {color:green}+1 tests included{color}.  The patch appears to include 4 new 
or modified test files.

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

    {color:green}+1 javadoc{color}.  There were no new javadoc warning messages.

    {color:green}+1 eclipse:eclipse{color}.  The patch built with 
eclipse:eclipse.

    {color:red}-1 findbugs{color}.  The patch appears to introduce 1 new 
Findbugs (version 2.0.3) warnings.

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

    {color:green}+1 core tests{color}.  The patch passed unit tests in 
hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api 
hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-applicationhistoryservice.

Test results: 
https://builds.apache.org/job/PreCommit-YARN-Build/7361//testReport/
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-YARN-Build/7361//artifact/patchprocess/newPatchFindbugsWarningshadoop-yarn-server-applicationhistoryservice.html
Console output: https://builds.apache.org/job/PreCommit-YARN-Build/7361//console

This message is automatically generated.

> Add Rolling Time To Lives Level DB Plugin Capabilities
> ------------------------------------------------------
>
>                 Key: YARN-3448
>                 URL: https://issues.apache.org/jira/browse/YARN-3448
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>            Reporter: Jonathan Eagles
>            Assignee: Jonathan Eagles
>         Attachments: YARN-3448.1.patch, YARN-3448.10.patch, 
> YARN-3448.2.patch, YARN-3448.3.patch, YARN-3448.4.patch, YARN-3448.5.patch, 
> YARN-3448.7.patch, YARN-3448.8.patch, YARN-3448.9.patch
>
>
> For large applications, the majority of the time in LeveldbTimelineStore is 
> spent deleting old entities record at a time. An exclusive write lock is held 
> during the entire deletion phase which in practice can be hours. If we are to 
> relax some of the consistency constraints, other performance enhancing 
> techniques can be employed to maximize the throughput and minimize locking 
> time.
> Split the 5 sections of the leveldb database (domain, owner, start time, 
> entity, index) into 5 separate databases. This allows each database to 
> maximize the read cache effectiveness based on the unique usage patterns of 
> each database. With 5 separate databases each lookup is much faster. This can 
> also help with I/O to have the entity and index databases on separate disks.
> Rolling DBs for entity and index DBs. 99.9% of the data are in these two 
> sections 4:1 ration (index to entity) at least for tez. We replace DB record 
> removal with file system removal if we create a rolling set of databases that 
> age out and can be efficiently removed. To do this we must place a constraint 
> to always place an entity's events into it's correct rolling db instance 
> based on start time. This allows us to stitching the data back together while 
> reading and artificial paging.
> Relax the synchronous writes constraints. If we are willing to accept losing 
> some records that we not flushed in the operating system during a crash, we 
> can use async writes that can be much faster.
> Prefer Sequential writes. sequential writes can be several times faster than 
> random writes. Spend some small effort arranging the writes in such a way 
> that will trend towards sequential write performance over random write 
> performance.



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