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From "Jim Kellerman (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-1177) Delay when client is located on the same node as the regionserver
Date Fri, 12 Jun 2009 05:52:07 GMT

    [ https://issues.apache.org/jira/browse/HBASE-1177?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12718723#action_12718723
] 

Jim Kellerman commented on HBASE-1177:
--------------------------------------

Tried running the read test backwards (reading 104 columns...6 columns). The first few rows
were slower, but the big blip still existed between 23...10 columns. Something is really goofy.

{code}
Read 1 row with 104 columns 100 times in 1170 ms
Read 1 row with 103 columns 100 times in 313 ms
Read 1 row with 102 columns 100 times in 820 ms
Read 1 row with 101 columns 100 times in 809 ms
Read 1 row with 100 columns 100 times in 403 ms
Read 1 row with 99 columns 100 times in 704 ms
Read 1 row with 98 columns 100 times in 317 ms
Read 1 row with 97 columns 100 times in 246 ms
Read 1 row with 96 columns 100 times in 169 ms
Read 1 row with 95 columns 100 times in 179 ms
...
Read 1 row with 24 columns 100 times in 65 ms
Read 1 row with 23 columns 100 times in 3999 ms
Read 1 row with 22 columns 100 times in 4000 ms
Read 1 row with 21 columns 100 times in 4000 ms
Read 1 row with 20 columns 100 times in 4000 ms
Read 1 row with 19 columns 100 times in 4000 ms
Read 1 row with 18 columns 100 times in 4000 ms
Read 1 row with 17 columns 100 times in 4000 ms
Read 1 row with 16 columns 100 times in 4000 ms
Read 1 row with 15 columns 100 times in 4000 ms
Read 1 row with 14 columns 100 times in 4000 ms
Read 1 row with 13 columns 100 times in 4000 ms
Read 1 row with 12 columns 100 times in 4000 ms
Read 1 row with 11 columns 100 times in 4000 ms
Read 1 row with 10 columns 100 times in 4000 ms
Read 1 row with 9 columns 100 times in 4000 ms
Read 1 row with 8 columns 100 times in 4000 ms
Read 1 row with 7 columns 100 times in 42 ms
{code}

Go figure...

> Delay when client is located on the same node as the regionserver
> -----------------------------------------------------------------
>
>                 Key: HBASE-1177
>                 URL: https://issues.apache.org/jira/browse/HBASE-1177
>             Project: Hadoop HBase
>          Issue Type: Bug
>    Affects Versions: 0.19.0
>         Environment: Linux 2.6.25 x86_64
>            Reporter: Jonathan Gray
>            Assignee: Jim Kellerman
>             Fix For: 0.20.0
>
>         Attachments: Contribution of getClosest to getRow time.jpg, Contribution of next
to getRow time.jpg, Contribution of seekTo to getClosest time.jpg, Elapsed time of RowResults.readFields.jpg,
getRow + round-trip vs # columns.jpg, getRow times.jpg, ReadDelayTest.java, RowResults.readFields
zoomed.jpg, screenshot-1.jpg, screenshot-2.jpg, screenshot-3.jpg, screenshot-4.jpg, zoom of
columns vs round-trip blowup.jpg
>
>
> During testing of HBASE-80, we uncovered a strange 40ms delay for random reads.  We ran
a series of tests and found that it only happens when the client is on the same node as the
RS and for a certain range of payloads (not specifically related to number of columns or size
of them, only total payload).  It appears to be precisely 40ms every time.
> Unsure if this is particular to our architecture, but it does happen on all nodes we've
tried.  Issue completely goes away with very large payloads or moving the client.
> Will post a test program tomorrow if anyone can test on a different architecture.
> Making a blocker for 0.20.  Since this happens when you have an MR task running local
to the RS, and this is what we try to do, might also consider making this a blocker for 0.19.1.

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