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From Richard Lowe <>
Subject RE: default required in
Date Thu, 19 Apr 2012 17:18:33 GMT
Yes it is possible. Put the following as the last line of your topology file:


So long as you don't have any DC or rack with this name your local node will not be able to
address any nodes that aren't explicitly given in its topology file.

However bear in mind that, whilst Cassandra won't try to use replication factor to store to
these 'unknown' nodes, their token may mean that the 'natural' home for a row is on a node
that is not addressable. This can create holes in your dataset and create situations where
data can 'disappear' because the bloom filter says the data is on a particular node (due to
its token) but the coordinator can't contact that node to get at the data.

Careful use of replication factor and NetworkTopologyStrategy can help with this, but you
should make sure that a node really doesn't need to contact the unknown nodes before marking
them as such.


From: Bill Au []
Sent: 19 April 2012 17:16
Subject: default required in

All the examples of that I have seen have a default entry assigning
unknown nodes to a specific data center and rack.  Is it possible to have Cassandra ignore
unknown nodes for the purpose of replication?


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