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https://issues.apache.org/jira/browse/YARN-3448?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15902243#comment-15902243
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Ravi Prakash commented on YARN-3448:
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Thanks for the awesome design and fix Jon! I've opened YARN-6311 for adding
documentation for this store.
> 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
> Fix For: 2.8.0, 3.0.0-alpha1
>
> Attachments: 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-3448.17.patch, YARN-3448.1.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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