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From "Zhijie Shen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-3448) Add Rolling Time To Lives Level DB Plugin Capabilities
Date Wed, 06 May 2015 05:00:00 GMT

    [ https://issues.apache.org/jira/browse/YARN-3448?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14529923#comment-14529923

Zhijie Shen commented on YARN-3448:

Jonathan, the patch looks good  to me overall. I tried it locally and everything seems to
work fine so far. Just some minor comments:

1. Why do we need to change {{hadoop-hdfs-client/pom.xml}}?

2. Why do we need fstConf?
184	      <groupId>de.ruedigermoeller</groupId>
185	      <artifactId>fst</artifactId>

3. We import {{*}} in RollingLevelDBTimelineStore.

4. Move it into serviceInit phase?
309	    if (conf.getBoolean(TIMELINE_SERVICE_TTL_ENABLE, true)) {
310	      deletionThread = new EntityDeletionThread(conf);
311	      deletionThread.start();
312	    }

5. I'm wondering it will have some compatibility problem, as previous user don't know they
need to handle this error code. On the other side, we will state ATSv1 stable in YARN-3539.
136	    public static final int EXPIRED_ENTITY = 7;

> 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
>          Components: timelineserver
>            Reporter: Jonathan Eagles
>            Assignee: Jonathan Eagles
>              Labels: BB2015-05-TBR
>         Attachments: YARN-3448.1.patch, YARN-3448.10.patch, YARN-3448.12.patch, YARN-3448.13.patch,
YARN-3448.14.patch, YARN-3448.15.patch, YARN-3448.16.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
> 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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