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From "He Liangliang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13984) Add option to allow caller to know the heartbeat and scanner position when scanner timeout
Date Tue, 22 Sep 2015 12:28:04 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13984?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14902488#comment-14902488
] 

He Liangliang commented on HBASE-13984:
---------------------------------------

"not in sort order" means for each row the scanner first fetch from storeHeap, then from joinedHeap,
but the kvs in joinedHeap may less than kvs from storeHeap so there is a final sort before
returning to client. This feature require break between rows just because the current implementation
does not support seek in the middle of a row for a new scanner.

Renamed nextCell.

Added a flag which controls the peek call.


> Add option to allow caller to know the heartbeat and scanner position when scanner timeout
> ------------------------------------------------------------------------------------------
>
>                 Key: HBASE-13984
>                 URL: https://issues.apache.org/jira/browse/HBASE-13984
>             Project: HBase
>          Issue Type: Improvement
>          Components: Scanners
>            Reporter: He Liangliang
>            Assignee: He Liangliang
>         Attachments: HBASE-13984-V1.diff, HBASE-13984-V2.diff, HBASE-13984-V3.diff, HBASE-13984-V3.patch,
HBASE-13984-V4.diff
>
>
> HBASE-13090 introduced scanner heartbeat. However, there are still some limitations (see
HBASE-13215). In some application, for example, an operation access hbase to scan table data,
and there is strict limit that this call must return in a fixed interval. At the same time,
this call is stateless, so the call must return the next position to continue the scan. This
is typical use case for online applications.
> Based on this requirement, some improvements are proposed:
> 1. Allow client set a flag whether pass the heartbeat (a result contains the scanner
position) to the caller (via ResultScanner next)
> 2. Allow the client pass a timeout to the server, which can override the server side
default value
> 3. When requested by the client, the server peek the next cell and return to the client
in the heartbeat message



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