CODEWITHSUNDEEP
cassandradatastax
DeejUK
DeejUK

Reputation: 13501

Consequences of all Cassandra Nodes being Seeds?

Is there any reason why it would be bad to have all Cassandra nodes be in the seed nodes list?

We're working on automated deployments of Cassandra, and so can easily maintain a list of every node that is supposed to be in the cluster and distribute this as a list of seed nodes to all existing nodes, and all new nodes on startup.

All the documentation I can find suggests having a minimum number of seeds, but doesn't clarify what would happen if all nodes were seeds. There is some mention of seeds being preferred in the gossip protocol, but it is not clear what the consequence would be if all nodes were seeds.

Upvotes: 1

Views: 387

Answers (1)

markc
markc

Reputation: 2158

There is no reason as far as I am aware that is is bad to have all nodes as seeds in your list. I'll post some doc links below to give you some background reading but to summarise; the seed nodes are used primarily for bootstrapping. Once a node is running it will maintain a list of nodes it has established gossip with for subsequent startups.

The only disadvantage of having too many is that the proceedure for replacing nodes if they are seed nodes is slightly different:

http://www.datastax.com/documentation/cassandra/2.0/cassandra/operations/ops_replace_seed_node.html

Further background reading: (note some of the older docs although superceded sometimes do contain more lengthy explanations)

http://www.datastax.com/docs/1.0/cluster_architecture/gossip http://www.datastax.com/documentation/cassandra/1.2/cassandra/initialize/initializeMultipleDS.html

Upvotes: 2

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