The CO (Client Nodes) take the Elastic HTTP requests as well as Kibana requests. I want to use the ReadOnlyRest plugin keeping Kibana in mind as well (still looking at the PRO options for Kibana).
The entire stack is constructed using CloudFormation Templates.
The question is - if I have to install ReadOnlyRest plugin - in which part of this ElasticStack would I install it? If its on the CO nodes - then because I’m using Cloudforamtion, both the CO Instances will get these installations done symmetrically. IS that ok?
Yes your understanding is correct. It’s sufficient to Install ReadonlyREST Free only in the HTTP-enabled ES nodes (the client nodes behind the elastic load balancer).
Think about ReadonlyREST Free (the Elasticsearch plugin) as a sort of stateless filter on the HTTP interface of an ES node. The rest of the cluster does not need to know about ROR being installed in a node.
The Kibana plugins (ROR PRO and ROR Enterprise) are synergic with ROR Free for ES. This means it’s a requirement for the Kibana plugins that the ES plugin is installed.