[jira] [Updated] (CASSANDRA-4650) RangeStreamer should be smarter when picking endpoints for streaming in case of N >=3 in each DC.

["Jonathan Ellis (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANDRA-4650?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jonathan Ellis updated CASSANDRA-4650:
--------------------------------------

    Labels: streaming  (was: performance)
    
> 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: Improvement
>          Components: Core
>    Affects Versions: 1.1.5
>            Reporter: sankalp kohli
>            Priority: Minor
>              Labels: streaming
>   Original Estimate: 24h
>  Remaining Estimate: 24h
>
> 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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