Es7: Can the seed_hosts value be dynamically updated?

During scaledowns, I want to update the seed_hosts value (to remove the deprovisoing nodes).
I want to apply this new value to all the nodes which are still remaining in the cluster.

  1. Is it required to update the seed_hosts value when a scale down occurs?
  2. How can I dynamically update the seed_hosts list?

No, not required, but it's good practice. Note that the seed_hosts value should only mention the master-eligible nodes, and it's rare to want to scale those down (there's normally always three of them).

DNS is a popular choice: create a DNS entry that resolves to the addresses of your three master nodes and set discovery.seed_hosts to the name of that entry.

Alternatively you can use file-based discovery or another discovery plugin.

Unfortunately, I have a different scenario.
Each node in my cluster is a master as well as a data node.
So a 36 node cluster will have 36 master eligible node and we have to support scale down form 36 ->1 node as well.

I believe in such scenarios, scale down becomes tricky. We need to evacuate these nodes so that quorum doesn't break but I think we should also update the seed_hosts.

That's very much not a recommended setup.

Nonetheless, there are docs describing how to remove master-eligible nodes from the cluster here:

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