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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, 15 May 2009 00:44:45 GMT

    [ https://issues.apache.org/jira/browse/HBASE-1177?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12709648#action_12709648
] 

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

When I did not deploy a region server on the same machine as the namenode and master, I got
much better times:

{code}
When run on node hosting region that is not the same as namenode or master:

Read 1 row with 7 columns 100 times in 113ms
Read 1 row with 8 columns 100 times in 4057ms
Read 1 row with 1000 columns 100 times in 10570ms

When run on node not hosting region and is not namenode or master:

Read 1 row with 7 columns 100 times in 109ms
Read 1 row with 8 columns 100 times in 121ms
Read 1 row with 1000 columns 100 times in 8838ms
{code}

So running an application on the same server as the namenode. master and region server definately
slows things down.

There is basically no difference in the test where we read 1 row with 7 columns.

Why the read 1 row with 8 columns or the read 1 row with 1000 columns is still slower if the
application is run on a different machine than the one hosting the region, is still a mystery.

Will continue investigation.......

> 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
>            Priority: Blocker
>             Fix For: 0.20.0
>
>         Attachments: ReadDelayTest.java
>
>
> 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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