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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-12790) Support fairness across parallelized scans
Date Thu, 15 Oct 2015 21:57:06 GMT

     [ https://issues.apache.org/jira/browse/HBASE-12790?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Andrew Purtell updated HBASE-12790:
    Attachment: PHOENIX_4.5.3-HBase-0.98-2317-SNAPSHOT.zip

In the interest of moving this forward we asked the perf guys on our Phoenix team to test
HBase 0.98.16-SNAPSHOT plus HBASE-12790 and Phoenix 4.5.3-SNAPSHOT with a small patch that
allows it to take advantage of the new Scan#getGroupingId API. The server side configuration
was updated to specify RoundRobinRPCScheduler for RPC scheduling. The comparison results are
attached as "PHOENIX_4.5.3-HBase-0.98-2317-SNAPSHOT.zip"

It's an indirect result in that we are viewing perf through the Phoenix lens, but I'm happy
to report there are no perf regressions found, only improvements. Therefore I have no concerns
in that regard about getting this committed.

I put up some comments on https://reviews.apache.org/r/32447. Getting there.

/cc [~jamestaylor]

> Support fairness across parallelized scans
> ------------------------------------------
>                 Key: HBASE-12790
>                 URL: https://issues.apache.org/jira/browse/HBASE-12790
>             Project: HBase
>          Issue Type: New Feature
>            Reporter: James Taylor
>            Assignee: ramkrishna.s.vasudevan
>              Labels: Phoenix
>         Attachments: AbstractRoundRobinQueue.java, HBASE-12790.patch, HBASE-12790_1.patch,
HBASE-12790_5.patch, HBASE-12790_callwrapper.patch, HBASE-12790_trunk_1.patch, PHOENIX_4.5.3-HBase-0.98-2317-SNAPSHOT.zip
> Some HBase clients parallelize the execution of a scan to reduce latency in getting back
results. This can lead to starvation with a loaded cluster and interleaved scans, since the
RPC queue will be ordered and processed on a FIFO basis. For example, if there are two clients,
A & B that submit largish scans at the same time. Say each scan is broken down into 100
scans by the client (broken down into equal depth chunks along the row key), and the 100 scans
of client A are queued first, followed immediately by the 100 scans of client B. In this case,
client B will be starved out of getting any results back until the scans for client A complete.
> One solution to this is to use the attached AbstractRoundRobinQueue instead of the standard
FIFO queue. The queue to be used could be (maybe it already is) configurable based on a new
config parameter. Using this queue would require the client to have the same identifier for
all of the 100 parallel scans that represent a single logical scan from the clients point
of view. With this information, the round robin queue would pick off a task from the queue
in a round robin fashion (instead of a strictly FIFO manner) to prevent starvation over interleaved
parallelized scans.

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