How to replicate only one index in ElasticSearch?

Question

elasticsearch

Hello!
I really need help with setting up replication in ElasticSearch. The fact is that I use CouchDB as the main database in the project, data is transferred from it via River to ElasticSearch. At the moment I have 4 Master-Master servers. Those. CouchDB are synchronized with each other, and ElasticSearch is synchronized through them.
Now there is a task to write a lot of logs. I really don't want to write them in CouchDB, so it was decided to write them immediately in ElasticSearch, in a separate index. But there was a question of synchronization of indexes among themselves.
If I now simply synchronize the elastics with each other, then the main data will “quadruple” for me, because Document IDs in elastic are different everywhere.
How can this be done without setting up a second Elastic on each server?
What if for the main index (which is not for logs) I specify the number of shards 1 and the number of replicas - 1. Is there a chance that he will still try to synchronize it with other servers?