How to make Mysqlnd_ms run each query on a different instance

Question

I have an AWS RDS with 1 read replica (total 2 instances). I'm planning to install mysqlnd_ms plugin so that I can have my request pointed to the database servers in round robin fashion.

I have 2 basic questions which I couldn't find direct answers in documentation

1. Using mysqlnd_ms, is there a way to say, not all select queries should point to slave(read replica). Each request should be alternatively pointed to the existing instances
2. Suppose if we run 2 queries per request, then does each of the query points to 1 instance? This means it will be opening 2 database connections for each request? Am I understanding this correctly

Answer 1

Create a json file and mention the path in

/etc/php.d/mysqlnd_ms.ini

file as below

mysqlnd_ms.config_file=/etc/mysqlnd_ms_cfg.json

Add the following code in json file

/etc/mysqlnd_ms_cfg.json

    {

        "myapp": {
            "master": {
                "master_0": {
                    "host": "RDS master instance IP/doamin name",
                    "port": 3306
                }
            },
            "slave": {
                "slave_0": {
                    "host": "RDS master instance IP/doamin name",
                    "port": 3306
                },
                "slave_1": {
                    "host": "RDS read replica instance IP/doamin name",
                    "port": 3306
                }
            },
            "filters": [
                "roundrobin"
            ]
        }
    }