cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Kyle Gibson <>
Subject Re: Replicating to all nodes
Date Fri, 15 Jul 2011 22:06:14 GMT
> The node (known as the "coordinating node" because it co-ordinates the
> request submitted by the client) will send the request to the nodes
> that are in the replica set for the row. The client need not care
> about which host it connects to, other than that it be "one of the
> ones in the correct cluster".
> Is this the source of confusion? There is never any issue with talking
> to the "wrong" node outside of the replica set. The client just
> doesn't care; Cassandra takes care of it.

That is not an issue that I feel confused about. I get the fact that
cassandra will proxy the data transfer between the coordinating node
and the node that actually has the data back to the client. I am not
concerned about talking with the "wrong" node.

I am concerned about the following scenario: N-1 nodes are down. This
implies that only 1 node is online and available for communication.
This node owns a specific token range. Yes, it can operate as a
coordinating node, but all of the other nodes are offline, they do not

> It sounds like you're worried about data ending up on nodes that are
> outside of the replica set, or that reads are done outside of the
> replica set. This is not something you need to worry about. Just
> submit your queries to the cluster and the appropriate nodes will be
> serving the requests.

I am worried that if only 1 node is active and online, and the other
N-1 nodes are inactive, down, and offline, that the cluster will not
be able to complete the operation, because not all of the data is
available on the 1 node that is up.

View raw message