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From "Lars Hofhansl (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 15:16:38 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6561?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13433203#comment-13433203
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Lars Hofhansl commented on HBASE-6561:
--------------------------------------

bq. So, we seek to column X+1, we need to skip all versions (because they have readpoint >
1) – so we keep reseeking until the end. That'd be crazy for sure.

That's exactly what I am seeing.

bq. Why does the Put throw off the Get? Because memStoreTS gets updated during the Get?

Somehow there's an older Get that did not finish (or is retried?), and the Puts keep piling
on versions that need to be skipped.

BTW. The idea with sorting leading with memstoreTS does not work, because for flush we need
them in normal key order.
                
> 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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