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From aaron morton <aa...@thelastpickle.com>
Subject Re: inconsistent hadoop/cassandra results
Date Tue, 08 Jan 2013 20:42:22 GMT
Assuming their were no further writes, running repair or using CL all should have fixed it.


Can you describe the inconsistency between runs? 

Cheers

-----------------
Aaron Morton
Freelance Cassandra Developer
New Zealand

@aaronmorton
http://www.thelastpickle.com

On 8/01/2013, at 2:16 AM, Brian Jeltema <brian.jeltema@digitalenvoy.net> wrote:

> I need some help understanding unexpected behavior I saw in some recent experiments with
Cassandra 1.1.5 and Hadoop 1.0.3:
> 
> I've written a small map/reduce job that simply counts the number of columns in each
row of a static CF (call it Foo) 
> and generates a list of every row and column count. A relatively small fraction of the
rows have a large number
> of columns; worst case is approximately 36 million. So when I set up the job, I used
wide-row support:
> 
>     ConfigHelper.setInputColumnFamily(job.getConfiguration(), "fooKS", "Foo", WIDE_ROWS);
// where WIDE_ROWS == true
> 
> When I ran this job using the default CL (1) I noticed that the results varied from run
to run, which I attributed to inconsistent
> replicas, since Foo was generated with CL == 1 and the RF == 3. 
> 
> So I ran repair for that CF on every node. The cassandra log on every node contains lines
similar to:
> 
>   INFO [AntiEntropyStage:1] 2013-01-05 20:38:48,605 AntiEntropyService.java (line 778)
[repair #e4a1d7f0-579d-11e2-0000-d64e0a75e6df] Foo is fully synced
> 
> However, repeated runs were still inconsistent. Then I set CL to ALL, which I presumed
would always result in identical
> output, but repeated runs initially continued to be inconsistent. However, I noticed
that the results seemed to
> be converging, and after several runs (somewhere between 4 and 6) I finally was producing
identical results on every run.
> Then I set CL to QUORUM, and again generated inconsistent results.
> 
> Does this behavior make sense?
> 
> Brian


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