[jira] [Commented] (YARN-5715) introduce entity prefix for return and sort order

["Sangjin Lee (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/YARN-5715?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15553462#comment-15553462 ] 

Sangjin Lee commented on YARN-5715:
-----------------------------------

During the call, I was thinking we might want to have a separate JIRA to deal with the YARN-generic entities, distributed shell, and MR, but on second thought I think it might be easier to do it in one patch. Let's see how it goes...

> introduce entity prefix for return and sort order
> -------------------------------------------------
>
>                 Key: YARN-5715
>                 URL: https://issues.apache.org/jira/browse/YARN-5715
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: timelineserver
>            Reporter: Sangjin Lee
>            Priority: Critical
>         Attachments: YARN-5715-YARN-5355.01.patch
>
>
> While looking into YARN-5585, we have come across the need to provide a sort order different than the current entity id order. The current entity id order returns entities strictly in the lexicographical order, and as such it returns the earliest entities first. This may not be the most natural return order. A more natural return/sort order would be from the most recent entities.
> To solve this, we would like to add what we call the "entity prefix" in the row key for the entity table. It is a number (long) that can be easily provided by the client on write. In the row key, it would be added before the entity id itself.
> The entity prefix would be considered mandatory. On all writes (including updates) the correct entity prefix should be set by the client so that the correct row key is used. The entity prefix needs to be unique only within the scope of the application and the entity type.
> For queries that return a list of entities, the prefix values will be returned along with the entity id's. Queries that specify the prefix and the id should be returned quickly using the row key. If the query omits the prefix but specifies the id (query by id), the query may be less efficient.
> This JIRA should add the entity prefix to the entity API and add its handling to the schema and the write path. The read path will be addressed in YARN-5585.



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