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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9467) write can be totally blocked temporarily by a write-heavy region
Date Fri, 13 Sep 2013 20:09:52 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9467?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13766885#comment-13766885
] 

Todd Lipcon commented on HBASE-9467:
------------------------------------

I don't have time to look at the patch itself, but one thing that comes to mind: is this a
compatible change? Or do you need to add a new client parameter of some time that tells the
server that it knows how to handle the new exception? It would be bad if existing clients
all started getting some ClassNotFoundException trying to unwrap the new exception type, and
actually failing rather than retrying. I don't know if that happens, but worth double checking
(eg run YCSB with an old client against a new server)
                
> write can be totally blocked temporarily by a write-heavy region
> ----------------------------------------------------------------
>
>                 Key: HBASE-9467
>                 URL: https://issues.apache.org/jira/browse/HBASE-9467
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Feng Honghua
>            Assignee: Feng Honghua
>         Attachments: HBASE-9467-trunk-v0.patch
>
>
> Write to a region can be blocked temporarily if the memstore of that region reaches the
threshold(hbase.hregion.memstore.block.multiplier * hbase.hregion.flush.size) until the memstore
of that region is flushed.
> For a write-heavy region, if its write requests saturates all the handler threads of
that RS when write blocking for that region occurs, requests of other regions/tables to that
RS also can't be served due to no available handler threads...until the pending writes of
that write-heavy region are served after the flush is done. Hence during this time period,
from the RS perspective it can't serve any request from any table/region just due to a single
write-heavy region.
> This sounds not very reasonable, right? Maybe write requests from a region can only be
served by a sub-set of the handler threads, and then write blocking of any single region can't
lead to the scenario mentioned above?
> Comment?

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