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.
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Erick Ramirez for the following reason: The question is answered, right answer was accepted
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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