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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