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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-1050) Allow regions to split around scanners
Date Sat, 20 Dec 2008 23:16:44 GMT

    [ https://issues.apache.org/jira/browse/HBASE-1050?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12658333#action_12658333
] 

stack commented on HBASE-1050:
------------------------------

I took a quick look.  It doesn't seem too bad.  Client already has notion of getting new scanners
as it moves across regions.  Would just need to make it keep last row fetched and then set
up new scanner on split region at the row that follows the last one fetched.  Batching of
scanner gets makes it a little more awkward.  Server-side, would need to throw NSRE if we
try to next on a closed region.  I'll take a deeper look monday.

> Allow regions to split around scanners
> --------------------------------------
>
>                 Key: HBASE-1050
>                 URL: https://issues.apache.org/jira/browse/HBASE-1050
>             Project: Hadoop HBase
>          Issue Type: Improvement
>          Components: client, regionserver
>            Reporter: Andrew Purtell
>            Assignee: Andrew Purtell
>            Priority: Blocker
>             Fix For: 0.20.0
>
>
> We have a number of scanners iterating over a table that also sees a lot of constant
write activity. If the scans are too frequent we will suppress splitting. At a lull then a
number of splits happen all at once, occasionally overwhelming DFS and causing file corruption.

> I wonder how much work it would be to split regions around scanners. Rather than wait
for scanner leases to expire, suspend/block the scanner, split the table, and then negotiate
with the client to continue. 

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