MySQL-Proxy Round Robin

Hi All,

I have Mysql-Proxy Server (IP: 192.168.190.142) and 03 DB servers, in there:

- DB Server 1: Read & Write
  (IP: 192.168.190.41)
- DB Server 2: Read
  (IP: 192.168.190.144)
- DB Server 3: Read
  (IP: 192.168.190.145)

I checked the DB Server 1 (Read & Write OK) & DB Server 3 (Read OK)
And DB Server 2 never read.

#vi /etc/mysql-proxy.cnf
[mysql-proxy]

user=root
proxy-address= 192.168.190.142:3306      #IP, port of proxy server
proxy-backend-addresses=192.168.190.41:3306       #IP, port of DB server for writting
proxy-read-only-backend-addresses=192.168.190.144:3306      #IP, port of DB server for read
proxy-read-only-backend-addresses=192.168.190.145:3306       #IP, port of DB server for read
proxy-lua-script=/usr/local/mysql-proxy/lua/rw-splitting.lua # script read-write
admin-lua-script=/usr/local/mysql-proxy/lua/admin-sql.lua # script management
log-file=/usr/local/mysql-proxy/log/mysql-proxy.log       #file log
log-level=warning
daemon=true            
keepalive=true

Where is the parameter for round robin that I can declare in this configuration above? Is it right?

Please give me your advices about this issue.

Thanks in advance,