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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 19:28:12 GMT

    [ https://issues.apache.org/jira/browse/HBASE-11724?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14095981#comment-14095981
] 

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

{quote}
Adding something like this? "A value of 0.5 means that there will be the same number of short-read
and long-read queues" and "A value > 0.5 means that there will be more long-read queues
then short-read queues" and "A value < 0.5 means that there will be less long-read queues
then short-read queues"
{quote}

Yeah.  Let me give some examples that could illustrate my confusion and help clarify.

hbase.ipc.server.callqueue.read.share = 1.0 
hbase.ipc.server.callqueue.scan.share = .5

Does this mean that writes are 0%, gets are 50% and scans are 50%?

hbase.ipc.server.callqueue.read.share = .5 
hbase.ipc.server.callqueue.scan.share = .5

Does this mean that writes are 0%, gets are 50% and scans are 50%?
Or, does this mean that writes are 50%, gets are 25% and scans are 25%?

{quote}
Why? "share" may be interpreted as a boolean but if you see 0 as default instead of false,
it is probably not a boolean.. then you read about the 0 and 1 edge case... and you may start
understanding that that probably is the limit...
otherwise, you are just the fancy user that wants to break things and set random crap as value...
{quote}

I'm not worried about fancy users, I'm worried about uninformed users that unknowingly break
things because they don't know or don't get an indication that they set a crap value.

{quote}
If you want I can add "the value must be between 0.0 and 1.0" to the doc... but you may want
to add that also to all the other fields that we have in hbase-default.xml
{quote}

Yes, I fact I strongly encourage this for other settings as well.  It is even better if the
code warns when there is a violation.  If we can add more guardrails so uninformed users can't
make silly mistakes (and get notified about it), hbase becomes easier to use and we avoid
bad situations preemptively.  


> 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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