Can I reload after a setting change in elasticsearch.yml?

Is there a way to only reload the settings and not the whole stack ?

If you have made changes to the Elasticsearch config you will need to restart the node(s) for it to take effect.

and if I do it node by node, there won't be any impact on the users right?
That would also be true for rebooting one master at the time?

What kind of changes have you made?

I removed some deprecated settings that were giving me critical errors in the Upgrade Assistant.

Then I suspect you should be able to do a rolling restart. If you have changed settings to enable or disable TLS you would have needed to do a full cluster restart.

@Christian_Dahlqvist Ok I tried rebooting one of my 3 nodes and Elasticsearch wouldn't start.

I have a critical error about "" being deprecated so I commented it in elasticsearch.yml. It didn't like that so I uncommented it and I was able to start the service.

If I don't remove it, I will still have my critical error so that's an issue...

I got this error in the log : bootstrap check failure [1] of [1]: the default discovery settings are unsuitable for production use; at least one of [discovery.seed_hosts, discovery.seed_providers, cluster.initial_master_nodes] must be configured