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From "Jonathan Lawlor (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13090) Progress heartbeats for long running scanners
Date Fri, 06 Mar 2015 20:51:39 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13090?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14350874#comment-14350874
] 

Jonathan Lawlor commented on HBASE-13090:
-----------------------------------------

bq. Doesn't RegionScanner get created when the scan starts? Can it not run the timer?

That's true, the RegionScanner is created when the scan starts. It also remains open Server-side
as long as the Client does not close it (as is the case in non-small scans). To keep all accounting
of the timer within the RegionScanner we could add a call to RegionScanner#updateTimeoutTimestamp
(or something along those lines) into RsRpcServices each time we either create or retrieve
the RegionScanner (would avoid accounting for timeouts within RsRpcServices). The timestamp
would need to be updated on each RsRpcServices#scan call to make sure that we aren't using
a previously defined timeout timestamp that would be too restrictive at this point. Then all
timeout information would be communicated to RsRpcServices via the newly defined NextState
from HBASE-11544.

> 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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