Cassandra- Replacing seed node without downtime

Question

I have a 3 node cassandra cluster with replication factor of 3 and also run on different az's in aws.

In my current setup I have all 3 nodes configured as seed nodes.(1 node per az). So when a seed node goes down, how can I bring it back up without downtime?

I cannot think of a proper way to do it. Because the first step is to remove the seed node from the seed node list and do a rolling restart of all the servers. When I do this, there is a duration when there is only one node online and since my application does queries with QUORUM it fails.

Is there a way to achieve this without downtime by only having 3 replicas ?

Thanks in advance.

Answer 1

Seed nodes are used for initial discovery of cluster's topology, and then all the nodes are discovered via gossip & continue to exchange information until next restart. If your seed node simply went down, then just start it, and it will connect the other seed nodes & get cluster information from them.

The removal of seed node & rolling restart is required only if you completely remove the node, and replace it with another (as described in documentation).