ElasticSearch with JSON Source generate from Mysql DB?

Dear ALL!
I`m bulding my search feature website and i just doing somthing with api _river try to indexing data in mysql data base i have some problems as.
1/ According ElasticSearch (ES) store data indexing data into Cluster/Node,when i index data from mysql as the same ?
2/i had generated Data from mysql to JSON file ,so how i can index data from source folder these JSON ? If compare perfomance with retrieve data index from mysql and from JSON file in folder which the best way?

thanks for read!