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From "Zhijie Shen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-3836) add equals and hashCode to TimelineEntity and other classes in the data model
Date Thu, 09 Jul 2015 01:51:05 GMT

    [ https://issues.apache.org/jira/browse/YARN-3836?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14619729#comment-14619729

Zhijie Shen commented on YARN-3836:

bq. I see that we're implementing the Comparable interface for all 3 types. I'm wondering
if it makes sense for them. What would it mean to order TimelineEntity instances? Does it
mean much? Where would it be useful? Do we need to implement it? The same questions go for
the other 2 types...

For example, compareTo of TimelineEntity is used to order the entities in the return set of
getEntities query. It would be better to return the entities ordered by timestamp instead
of randomly.

bq. his is an open question. Is the id alone the identity or does the timestamp together form
the identity? Do we expect users of TimelineEvent always be able to provide the timestamp?
Honestly I'm not 100% sure what the contract is, and we probably want to make it explicit
(and add it to the javadoc). Thoughts?

In ATS v1, we actually use id + timestamp to uniquely identify an event. On merit of doing
this is to let the app to put the same event multiple times. For example, a job can request
resource many times. Every time it can put a RESOURCE_REQUEST event with a unique timestamp
and fill in the resource information.

> add equals and hashCode to TimelineEntity and other classes in the data model
> -----------------------------------------------------------------------------
>                 Key: YARN-3836
>                 URL: https://issues.apache.org/jira/browse/YARN-3836
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: timelineserver
>    Affects Versions: YARN-2928
>            Reporter: Sangjin Lee
>            Assignee: Li Lu
>         Attachments: YARN-3836-YARN-2928.001.patch
> Classes in the data model API (e.g. {{TimelineEntity}}, {{TimelineEntity.Identifer}},
etc.) do not override {{equals()}} or {{hashCode()}}. This can cause problems when these objects
are used in a collection such as a {{HashSet}}. We should implement these methods wherever

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