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https://issues.apache.org/jira/browse/HBASE-9467?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13763699#comment-13763699
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Todd Lipcon commented on HBASE-9467:
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Sorry, hit submit too quickly... I meant to add that this approach is much
better because it also helps with the problem of multiple different priority
clients hitting the same region -- for example, a low priority MR job doing
bulk puts into a region at the same time as a latency sensitive web app is
doing single row requests. If you could set the watermarks for the low priority
clients differently than high-priority clients, then rejecting the low priority
ones and making them retry on the client side will leave room (both
handler-wise and capacity wise) for the high priority ones to get in without
sitting in lengthy RPC queues.
> 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
> Priority: Minor
>
> 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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