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From "sankalp kohli (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-4650) RangeStreamer should be smarter when picking endpoints for streaming in case of N >=3 in each DC.
Date Wed, 12 Sep 2012 00:02:08 GMT
sankalp kohli created CASSANDRA-4650:
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             Summary: RangeStreamer should be smarter when picking endpoints for streaming
in case of N >=3 in each DC.  
                 Key: CASSANDRA-4650
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4650
             Project: Cassandra
          Issue Type: Bug
          Components: Core
    Affects Versions: 1.1.5
            Reporter: sankalp kohli
            Priority: Minor


getRangeFetchMap method in RangeStreamer should pick unique nodes to stream data from when
number of replicas in each DC is three or more. 
When N>=3 in a DC, there are two options for streaming a range. Consider an example of
4 nodes in one datacenter and replication factor of 3. 
If a node goes down, it needs to recover 3 ranges of data. With current code, two nodes could
get selected as it orders the node by proximity. 
We ideally will want to select 3 nodes for streaming the data. We can do this by selecting
unique nodes for each range.  

Advantages:
This will increase the performance of bootstrapping a node and will also put less pressure
on nodes serving the data. 

Note: This does not affect if N < 3 in each DC as then it streams data from only 2 nodes.


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