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From "Jonathan Hsieh (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-11724) Add to RWQueueRpcExecutor the ability to split get and scan handlers
Date Wed, 13 Aug 2014 17:50:12 GMT

    [ https://issues.apache.org/jira/browse/HBASE-11724?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14095789#comment-14095789
] 

Jonathan Hsieh commented on HBASE-11724:
----------------------------------------

{quote}
Isn't that all explained in the hbase-default doc?
A value of 0 or 1 indicate to use the same set of queues for gets and scans.
any other value is multiplied by the number of read queues that you have.
{quote}

I'm asking for a better explanation in the hbase-default.xml description -- if I were a user
looking only at this file for how to set the value, I don't know if what valid values are.
As worded "A value of 0 or 1 indicate to use the same set of queues for gets and scans." could
be interpreted to mean that when I set the value to '0' queues are shared, and when I set
the value to '1' the queues are also shared. It seems like could set it to 42 to turn off
the get/scan sharing.  The fact that it is a float ratio between 0 and 1 is important to note
here.

{quote}
Basically it does what you expect, "give me more scans" or "give me less scans" if you want
to do the math to specify the right number of queues good for you, otherwise the will do what
is right based on what you specified.
{quote}

if I just look at the hbase-default.xml I don't know what to expect.  I want to you make it
clear for the user in the in hbase-default.xml

{quote}
aside the fact that I don't see validation in any place where we have conf values, here all
the value that you set will result in a valid settings. < 0 will result in 0, > 0 will
result in 1
{quote}

where is this enforced?  I didn't see it in this patch and theese values get used in the calculations
of # of counts.  As a user I could put values in like -1 or 42 and not know it was silly.

> Add to RWQueueRpcExecutor the ability to split get and scan handlers
> --------------------------------------------------------------------
>
>                 Key: HBASE-11724
>                 URL: https://issues.apache.org/jira/browse/HBASE-11724
>             Project: HBase
>          Issue Type: New Feature
>          Components: IPC/RPC
>            Reporter: Matteo Bertozzi
>            Assignee: Matteo Bertozzi
>            Priority: Minor
>             Fix For: 2.0.0
>
>         Attachments: HBASE-11724-v0.patch
>
>
> RWQueueRpcExecutor has the devision between reads and writes requests, but we can split
also small-reads and long-reads. This can be useful to force a deprioritization of scans on
the RS.



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