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From "Serediuk, Adam" <Adam.Sered...@serialssolutions.com>
Subject Re: Range Slice Issue
Date Tue, 03 May 2011 17:47:08 GMT
I just ran a test and we do not see that behavior with dynamic snitch disabled. All nodes appear
to be doing local reads as expected.


On May 3, 2011, at 10:37 AM, Jonathan Ellis wrote:

> Do you still see this behavior if you disable dynamic snitch?
> 
> On Tue, May 3, 2011 at 12:31 PM, Serediuk, Adam
> <Adam.Serediuk@serialssolutions.com> wrote:
>> We appear to have encountered an issue with cassandra 0.7.5 after upgrading
>> from 0.7.2. While doing a batch read using a get_range_slice against the
>> ranges an individual node is master for we are able to reproduce
>> consistently that the last two nodes in the ring, regardless of the ring
>> size (we have a 60 node production cluster and a 12 node test cluster)
>> perform this read over the network using replicas of executing locally.
>> Every other node in the ring successfully reads locally.
>> To be sure there were no data consistency issues we performed a nodetool
>> repair against both of these nodes and the issue persists. We also tried
>> truncating the column family and repopulating, but the issue remains.
>> This seems to be related to CASSANDRA-2286 in 0.7.4. We always want to read
>> data locally if it is available there. We
>> use Cassandra.Client.describe_ring() to figure out which machine in the
>> ring is master for which TokenRange. I then compare the master for
>> each TokenRange against the localhost to find out which token ranges
>> are owned by the local machine (remote reads are too slow for this type
>> of batch processing). Once I know which TokenRanges are on
>> each machine locally I get evenly sized splits using
>> Cassandra.Client.describe_splits().
>> 
>> Adam
>> 
> 
> 
> 
> -- 
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder of DataStax, the source for professional Cassandra support
> http://www.datastax.com
> 



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