I am new to Elasticsearch. I would like to understand if it is possible to set up 3 Master nodes as part of the same cluster. If possible, what would be the advantage/ use case scenario that prompts multiple Master nodes to be setup as part of the same cluster?
You can have multiple master-eligible nodes, but only one will ever be the active master. Note that in this case you should set
2, and however many master-eligible nodes you have this setting should be equal to a quorum (just don't ever have only two master-eligible nodes because then a quorum is two and you don't get high-availability).
For high-availability (if the active master falls down, a new one can be elected from the remaining eligible nodes and your cluster can keep on keeping on).