install and set up latest haproxy for four nodes

deploy_haproxy.sh

# scientific linux 6.4
# lb node - no sql on this node
# sql nodes: db1, db2, db3, db4

yum -y update
yum -y install gcc
useradd haproxy
wget http://haproxy.1wt.eu/download/1.4/src/haproxy-1.4.24.tar.gz
tar zxvf haproxy-1.4.24.tar.gz
cd haproxy-1.4.24
make install
mkdir -v /etc/haproxy

tee /etc/haproxy/haproxy.cfg <<EOF
global
       log 127.0.0.1 local0
       maxconn 4096
       user haproxy
       group haproxy
       daemon

defaults
       log global
       mode tcp
       option tcplog
       option dontlognull
       retries 3
       option redispatch
       maxconn 2000
        contimeout  3600000
        clitimeout  3600000
        srvtimeout  3600000
       stats enable
       stats scope .

frontend mysql_cluster
       bind mysql_lb:3306
       default_backend mysql_cluster

backend mysql_cluster
       mode tcp
       balance roundrobin
       option  mysql-check user haproxyUser
       server  db1 db1:3306 check
       server  db2 db2:3306 check
       server  db3 db3:3306 check
       server  db4 db4:3306 check

listen stats *:80
       mode http
       option httpclose
       balance roundrobin
       stats uri /
       stats realm Haproxy\ Statistics
       stats auth admin:admin
EOF

mysql -hdb1-uroot -p -e "GRANT ALL ON *.* to 'haproxyUser'@'%' IDENTIFIED BY '';"
mysql -hdb2-uroot -p -e "GRANT ALL ON *.* to 'haproxyUser'@'%' IDENTIFIED BY '';"
mysql -hdb3-uroot -p -e "GRANT ALL ON *.* to 'haproxyUser'@'%' IDENTIFIED BY '';"
mysql -hdb4-uroot -p -e "GRANT ALL ON *.* to 'haproxyUser'@'%' IDENTIFIED BY '';"

/usr/local/sbin/haproxy -f /etc/haproxy/haproxy.cfg -V

# be sure to modify iptables accordingly