DataStax Academy FAQ

DataStax Academy migrated to a new learning management system (LMS) in July 2020. We are also moving to a new Cassandra Certification process so there are changes to exam bookings, voucher system and issuing of certificates.

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chandrasekar.b03_190734 avatar image
chandrasekar.b03_190734 asked ·

What is the difference between seed nodes and other nodes in a cluster?

In DS 201 course, It has been told that when a new node is added, seed node helps to add the node to the cluster. I wanna know the purpose of seed nodes in cassandra, how it adds the new node to the cluster and the difference between the seed nodes and the other nodes.

cassandraseeds
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bettina.swynnerton answered ·

As the primary purpose, seed nodes allow a new node to find the cluster on the very first startup (bootstrap). To learn the topology of the ring, a joining node contacts one of the nodes in its seeds list (as configured in the cassandra.yaml configuration file).

As a secondary purpose, seeds nodes also help gossip in the cluster. Nodes in your ring tend to send Gossip message to seeds more often. By having all of the nodes in the cluster gossip regularly with the same set of seeds, schema and state changes propagate regularly throughout the cluster.

Other than that, there is nothing special about seed nodes, All nodes in the ring are peers. You can make any node a seed at any time, but the general recommendation is that all nodes list the same seed nodes in their configuration, due to the gossip benefit mentioned above.

Have a look at the Cassandra FAQ:

https://cassandra.apache.org/doc/latest/faq/index.html#what-are-seeds

I hope this helps!

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