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From "Rohith Sharma K S (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-5585) [Atsv2] Add a new filter fromId in REST endpoints
Date Wed, 07 Sep 2016 11:23:21 GMT

    [ https://issues.apache.org/jira/browse/YARN-5585?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15470338#comment-15470338

Rohith Sharma K S commented on YARN-5585:

One of the challenge for supporting fromId is to iterate in forward or backward? This dilemma
is mainly due to TimelineEntity#compareTo implementation where in sorted in descending order
if creation time is null otherwise sorted in ascending order of ID. 
Say entities from entity-1 to entity-10 then 
# If entities stored without creationtime, then getEntities has output ascending order of
ID i.e enitity-1 to entity-10.
# If entities stored with creationtime, then getEntities has output descending order of ID
i.e enitity-10 to entity-1.

When limit and fromId is applied on both the cases, the expected output changes respectively.

Say limit=5 and fromId=entity-5 then in first case, user expect entity-6 to entity-10 because
user has already got entity-1 to entity-5 on previous call. In second case, user expect entity-4
to entity-1. This is tedious task to differentiate between forward or backward iteration from
storage level. 

I think anyway this can not be achieved from storage level because of async storage of entities.
And this can be achieved at TimelineEntityReader having another loop. Cons is this would lead
to another loop in the code. 

> [Atsv2] Add a new filter fromId in REST endpoints
> -------------------------------------------------
>                 Key: YARN-5585
>                 URL: https://issues.apache.org/jira/browse/YARN-5585
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: timelinereader
>            Reporter: Rohith Sharma K S
>            Assignee: Rohith Sharma K S
>         Attachments: YARN-5585.v0.patch
> TimelineReader REST API's provides lot of filters to retrieve the applications. Along
with those, it would be good to add new filter i.e fromId so that entities can be retrieved
after the fromId. 
> Example : If applications are stored database, app-1 app-2 ... app-10.
> *getApps?limit=5* gives app-1 to app-10. But to retrieve next 5 apps, it is difficult.
> So proposal is to have fromId in the filter like *getApps?limit=5&&fromId=app-5*
which gives list of apps from app-6 to app-10. 
> This is very useful for pagination in web UI.

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