Elasticsearch Cluster Adding node

Elastic Stack Elasticsearch
#1

Hi,
I want to switch from single node elasticsearch to three node cluster without the data loss. For that, I have modified the configuration files correctly.
Let node1 be the one with data and node2, node3 are new nodes, if I restart the node1 first, then node2 and then node3, the data isn't lost and the cluster is formed successfully.
But if I restart node2 first then node3 and then node1, then two different clusters are formed, one containing node2 and node3, another node1 acting as single node cluster with only master node.
i want answers for these:

  1. is it mandatory to restart the node with data first?
  2. without losing data can I add node1 to the cluster with nodes node2 and node3?
  3. is it always mandatory for new node to be empty i.e. data should not be there?
#2

What version are you running.

#3

Hi @warkolm elasticsearch version is 7.4.2

#4

https://www.elastic.co/guide/en/elasticsearch/reference/current/add-elasticsearch-nodes.html goes into more detail and links to other parts of the docs that should help here.

You cannot have data on nodes 2 and 3 and then try to add that to the cluster that is node 1. That is essentially trying to merge 2 clusters, which isn't allowed.

#5

New nodes need to be added to an existing cluster so the node currently holding data need to be up first.

No. Node 1 has already formed a cluster and can not join another cluster without losing all data.

Yes.