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https://issues.apache.org/jira/browse/YARN-3901?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14729886#comment-14729886
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Vrushali C commented on YARN-3901:
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bq. From the code I can see we add the newly created cell to the list of cells 
(cells.add(someNewCell)). Is this operation only modifying the returned value 
of the next call, or it permanently writes the aggregated values back to HBase? 
This may sound silly but I'm not very familiar with the observer coprocessors.

Yes, in this code, we are only "reading" or returning back cells to the client 
(hbase client). But when we add in the compaction/flush coprocessors, they will 
write back to hbase as well. 

bq. Maybe a name that is more specific will help? How about something like 
AggregationPutAttribute?
Hmm. It's not really an attribute for the Put, it's more like the 
characteristic of the cell value itself. We could use these attributes outside 
of Aggregation as well, so don't want the agg prefix here. Still thinking what 
to call it. Perhaps FlowValueAttribute? 

> Populate flow run data in the flow_run & flow activity tables
> -------------------------------------------------------------
>
>                 Key: YARN-3901
>                 URL: https://issues.apache.org/jira/browse/YARN-3901
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: timelineserver
>            Reporter: Vrushali C
>            Assignee: Vrushali C
>         Attachments: YARN-3901-YARN-2928.1.patch, 
> YARN-3901-YARN-2928.2.patch, YARN-3901-YARN-2928.3.patch, 
> YARN-3901-YARN-2928.WIP.2.patch, YARN-3901-YARN-2928.WIP.patch
>
>
> As per the schema proposed in YARN-3815 in 
> https://issues.apache.org/jira/secure/attachment/12743391/hbase-schema-proposal-for-aggregation.pdf
> filing jira to track creation and population of data in the flow run table. 
> Some points that are being  considered:
> - Stores per flow run information aggregated across applications, flow version
> RM’s collector writes to on app creation and app completion
> - Per App collector writes to it for metric updates at a slower frequency 
> than the metric updates to application table
> primary key: cluster ! user ! flow ! flow run id
> - Only the latest version of flow-level aggregated metrics will be kept, even 
> if the entity and application level keep a timeseries.
> - The running_apps column will be incremented on app creation, and 
> decremented on app completion.
> - For min_start_time the RM writer will simply write a value with the tag for 
> the applicationId. A coprocessor will return the min value of all written 
> values. - 
> - Upon flush and compactions, the min value between all the cells of this 
> column will be written to the cell without any tag (empty tag) and all the 
> other cells will be discarded.
> - Ditto for the max_end_time, but then the max will be kept.
> - Tags are represented as #type:value. The type can be not set (0), or can 
> indicate running (1) or complete (2). In those cases (for metrics) only 
> complete app metrics are collapsed on compaction.
> - The m! values are aggregated (summed) upon read. Only when applications are 
> completed (indicated by tag type 2) can the values be collapsed.
> - The application ids that have completed and been aggregated into the flow 
> numbers are retained in a separate column for historical tracking: we don’t 
> want to re-aggregate for those upon replay
> 



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