[jira] Updated: (HBASE-1177) Delay when client is located on the same node as the regionserver

["Jonathan Gray (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-1177?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jonathan Gray updated HBASE-1177:
---------------------------------

    Attachment: ReadDelayTest.java

This is not meant for contribution, I have something much more generic if we want to add something about this to tests.

Test creates table, imports rows, and performs random reads for two differently sized rows.  The 7 column rows will be fetched quickly, 8 column rows show the 40ms delay behavior.

{code}
> java RandomReadTest
09/02/02 20:54:53 INFO client.HBaseAdmin: Enabled table test_table
Read 1 row with 7 columns 100 times in 66ms
Read 1 row with 8 columns 100 times in 4001ms
{code}

> 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
>            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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