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https://issues.apache.org/jira/browse/HBASE-16048?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15334722#comment-15334722
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Vrushali C commented on HBASE-16048:
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One use case is the next gen Timeline Service in YARN
https://issues.apache.org/jira/browse/YARN-2928
We are using hbase as the backend for all yarn applications' metrics and other
statistics and we make use of a coprocessor to do real time aggregation at the
flow level (across yarn apps). This coprocessor has been implemented by
extending the BaseRegionObserver.
The code is at branch YARN-2928 on hadoop and is gearing up for merge to trunk
on hadoop. The coprocessor is at
org.apache.hadoop.yarn.server.timelineservice.storage.flow.FlowRunCoprocessor
and the scanner to read/aggregate the values from cells from the table is at
org.apache.hadoop.yarn.server.timelineservice.storage.flow.FlowScanner
I can go into more details about the readless aggregation implementation and
other details if you'd like.
> Consider tagging InternalScanner with
> LimitedPrivate(HBaseInterfaceAudience.COPROC)
> ------------------------------------------------------------------------------------
>
> Key: HBASE-16048
> URL: https://issues.apache.org/jira/browse/HBASE-16048
> Project: HBase
> Issue Type: Improvement
> Reporter: Ted Yu
>
> Some methods (preCompact, preCompactScannerOpen, preFlush,
> preFlushScannerOpen, etc) of BaseRegionObserver take InternalScanner as input
> argument as well as the return type.
> BaseRegionObserver is tagged with
> @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC) but
> InternalScanner is tagged with @InterfaceAudience.Private.
> This JIRA is to discuss tagging InternalScanner with
> @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC).
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