Clever Geek Handbook

Can all cassandra nodes be set as seeds?

I am interested in speeding up the bootstrapping process of the cluster and adding / removing nodes (in case of deleting a node, most of the time will be spent deleting a node). I saw in the original code that the nodes that are seeds are not loaded and therefore do not sleep for 30 seconds, waiting for the gossip to stabilize. Thus, if all nodes are declared as seeds, the cluster creation process will run 30 seconds faster. My question is, is this ok? and what are the disadvantages of this? Is there a hidden requirement in cassandra that we have at least one unseeded node to do the bootstrap (as suggested in the answer to the next question )? I know I can cut RING_DELAY

by changing/etc/cassandra/cassandra-env.sh

but if you just set all the nodes as seeds it will be better or faster in some way, it might be better. (Intuitively, there must be a downside to the fact that all nodes are seeds, as it appears to severely improve startup times.)

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Good question. Seeding all nodes is not recommended. You want new nodes and nodes to appear after switching to automatic migration of correct data. The boot process does this. When initializing a new cluster with no data, disable boot. For data consistency, the bootload must be performed at a different time. In Cassandra 2.1, a new startup option was added - Dcassandra.auto_bootstrap = false. You run Cassandra with the option to temporarily enable auto_bootstrap = false until there is node. When node returns, auto_bootstrap = true is in effect by default. People are less likely to continue indefinitely without bootstrapping after creating a cluster - no need to go back and forth setting up yaml on each node.

In multiple datacenter clusters, the visit list must include at least one node from each datacenter. To prevent partitions in gossip links, use the same seed node list across all nodes in the cluster. This is important the first time you run node.



These guidelines are mentioned in several 2.1 pages of the Cassandra doc: http://www.datastax.com/documentation/cassandra/2.1/cassandra/gettingStartedCassandraIntro.html .

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