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From Hontvári József Levente <hontv...@flyordie.com>
Subject Re: is it possible to read obsolete data after write?
Date Mon, 20 Feb 2012 15:25:35 GMT
The appearance of the old rows were caused by old timestamps set on 
columns (which in turn caused by some ThreadLocals which were not 
cleaned up).  Since I fixed the timestamp, all rows returned corresponds 
to their latest saved state in each and every case.

On 2012.02.20. 13:32, Hontvári József Levente wrote:
> I noticed a strange phenomenon with Cassandra, and I would like to 
> know if this is something completely impossible, or not.
>
> As you can see in the log extract below, as new versions of a row is 
> written out, the reads returns obsolete data after a while (they read 
> version 78 when 79 and even 80 is already written out). There is only 
> a single Cassandra node in the cluster, the client is on the same 
> local network, there are about 10 rows written and read per seconds. I 
> would think that in this test environment I should not see any 
> obsolete data at all. But actually I have thousands of log entries 
> after a few hours of test, which say that the row which was read does 
> not match the latest data which was written.
>
> I checked in detail the history of another node, and it seems that 
> eventually I receive an up-to-date row, but it took once 10 and once 
> 15 minutes in this specific case.
>
> (FYI: I am just started to evaluate Cassandra, without any significant 
> experience.)
>
>            09:43:46Z Persisting version=77
> GOOD       09:45:20Z Loading version=77
>            09:45:21Z Persisting version=78
> GOOD       09:46:23Z Loading version=78
>            09:46:23Z Persisting version=79
> WRONG!     09:47:12Z Loading version=78
>            09:47:12Z Persisting version=80
> WRONG!!    09:49:20Z Loading version=78
>            09:49:20Z Persisting version=81
>
>
>


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