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https://issues.apache.org/jira/browse/HBASE-13090?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14350782#comment-14350782
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Jonathan Lawlor commented on HBASE-13090:
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bq. Why does RsRpcServices have to be involved? Could remaining scan time not
be up in RegionScanner?
I think RsRpcServices needs to be involved because it has the global view of
when the scan started. A particular call to RegionScanner#nextRaw may not
necessarily cause a timeout, but multiple calls to RegionScanner#nextRaw must
be made in order to form the ScanResponse. In other words, a timeout may not be
caused by a single call to RegionScanner#nextRaw but rather the accumulated
time of all calls necessary to form the ScanResponse.
> Progress heartbeats for long running scanners
> ---------------------------------------------
>
> Key: HBASE-13090
> URL: https://issues.apache.org/jira/browse/HBASE-13090
> Project: HBase
> Issue Type: New Feature
> Reporter: Andrew Purtell
>
> It can be necessary to set very long timeouts for clients that issue scans
> over large regions when all data in the region might be filtered out
> depending on scan criteria. This is a usability concern because it can be
> hard to identify what worst case timeout to use until scans are
> occasionally/intermittently failing in production, depending on variable scan
> criteria. It would be better if the client-server scan protocol can send back
> periodic progress heartbeats to clients as long as server scanners are alive
> and making progress.
> This is related but orthogonal to streaming scan (HBASE-13071).
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