HAProxy MySQL Load Balancing on Gentoo Linux

Config section

listen mysql-cluster
    bind *:3306
    mode    tcp
    option  mysql-check user haproxy_check
    balance leastconn
    server db1 192.168.1.10:3306 check weight 1
    server db2 192.168.1.11:3306 check weight 1
    server db3 192.168.1.12:3306 check weight 1

Create HAProxy check user on each DB node

CREATE USER 'haproxy_check'@'%';
FLUSH PRIVILEGES;

Validate and reload

haproxy -c -f /etc/haproxy/haproxy.cfg
systemctl reload haproxy

Test

mysql -h 127.0.0.1 -P 3306 -u appuser -p -e "SELECT @@hostname;"
# Repeat to see requests distributed