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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6561) Gets/Puts with many columns send the RegionServer into an "endless" loop
Date Mon, 13 Aug 2012 15:44:38 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6561?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13433226#comment-13433226
] 

stack commented on HBASE-6561:
------------------------------

bq. Another option is to have the MemStoreScanner memorize the last key it iterated to (for
both the kvSet and tailSet) and use that to build tailSet first in reseek (i.e. the closest
we can get to save the iterator state).

That could work.  I was worried something could be inserted between our get of last key and
build of tailset but should be fine since the read point will be lagging the write point used
by the insertion?
                
> Gets/Puts with many columns send the RegionServer into an "endless" loop
> ------------------------------------------------------------------------
>
>                 Key: HBASE-6561
>                 URL: https://issues.apache.org/jira/browse/HBASE-6561
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>             Fix For: 0.96.0, 0.94.2
>
>         Attachments: 6561-0.94.txt, 6561-0.96.txt
>
>
> This came from the mailing this:
> We were able to replicate this behavior in a pseudo-distributed hbase
> (hbase-0.94.1) environment. We wrote a test program that creates a test
> table "MyTestTable" and populates it with random rows, then it creates a
> row with 60,000 columns and repeatedly updates it. Each column has a 18
> byte qualifier and a 50 byte value. In our tests, when we ran the
> program, we usually never got beyond 15 updates before it would flush
> for a really long time. The rows that are being updated are about 4MB
> each (minues any hbase metadata).
> It doesn't seem like it's caused by GC. I turned on gc logging, and
> didn't see any long pauses. This is the gc log during the flush.
> http://pastebin.com/vJKKXDx5
> This is the regionserver log with debug on during the same flush
> http://pastebin.com/Fh5213mg
> This is the test program we wrote.
> http://pastebin.com/aZ0k5tx2
> You should be able to just compile it, and run it against a running
> HBase cluster.
> $ java TestTable
> Carlos

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