Significance/Role of Action and Gateway forders in elasticsearch server

Elastic Stack Elasticsearch
1

I would like to know what the files in action and gateway folder do in general,because while debugging elasticsearch i got some errors in these files.

Thanks

2

org.elasticsearch.gateway is largely about starting up the cluster after a restart: finding existing shard copies and allocating them, etc.

org.elasticsearch.action is where many transport actions are defined, along with their requests and responses.

3

I have one question, i tried to remove the inter-node communication in elasticsearch by closing the connection in transportService.java.
I got the following warning logs,
[2019-03-29T11:59:01,317][WARN ][o.e.g.Gateway ] [node-0] failed to fetch state from node
org.elasticsearch.action.FailedNodeException: Failed node [X9b9979VSuyrV4Pt7j6RKA]

Caused by: java.lang.IllegalStateException: can't send request to a null connection
[2019-03-29T11:59:31,328][DEBUG][o.e.a.a.c.n.s.TransportNodesStatsAction] [node-0] failed to execute on node [X9b9979VSuyrV4Pt7j6RKA]
java.lang.IllegalStateException: can't send request to a null connection

But i can send the rest requests that is port 9200 is still accessible .

Does that mean inter-node communication has stopped.

4

I've no idea. It certainly sounds like something isn't working any more.