1.haproxy安装（仅一个节点即可）
下载地址：http://www.haproxy.org/，选择最新稳定版。这里我选择数据节点ddb169作为haproxy的负载均衡服务器
[root@db169 soft]# tar -zxvf haproxy-1.5.3.tar.gz
[root@db169 soft]# cd haproxy-1.5.3
[root@db169 haproxy-1.5.3]# make TARGET=linux2628
[root@db169 haproxy-1.5.3]# make install
[root@db169 haproxy-1.5.3]# mkdir /etc/haproxy;cp examples/haproxy.cfg /etc/haproxy/
[root@db169 haproxy-1.5.3]# groupadd -g 1001 haproxy
[root@db169 haproxy-1.5.3]# useradd -g haproxy haproxy
2.配置haproxy（仅一个节点即可）
配置haproxy.cnf文件
[root@db169 haproxy-1.5.3]# mkdir /etc/haproxy/
[root@db169 haproxy-1.5.3]# cat /etc/haproxy/haproxy.cfg
# this config needs haproxy-1.1.28 or haproxy-1.2.1
global
log 127.0.0.1 local0
log 127.0.0.1 local1 notice
#log loghost local0 info
maxconn 4096
chroot /usr/share/haproxy
uid haproxy
gid haproxy
daemon
#debug
#quiet
pidfile /var/run/haproxy.pid
defaults
log global
mode http
#option httplog
option dontlognull
retries 3
redispatch
maxconn 2000
contimeout 5000
clitimeout 50000
srvtimeout 50000
frontend pxc-front #描述允许客户端连接的监听套接字
bind *:3307
mode tcp
default_backend pxc-back #当没有匹配use_backend时，默认的backend
frontend stats-front
bind *:8099
mode http
default_backend stats-back
backend pxc-back #描述进来的连接将转发到哪些后端服务器
mode tcp
balance leastconn #负载均衡算法，使用最少连接算法，适合长连接应用
option httpchk #启用HTTP协议检查服务器监控状态，通过调用脚本检查节点的状态
server db169 192.168.1.169:3306 check port 9200 inter 12000 rise 3 fall 3 #fall连续3次检查错误后，将表明服务器死亡，默认为3；inter连续两次检查的间隔时间值，单位为毫秒默认为2s；rise连续3次检查成功，表明服务可用
server db172 192.168.1.172:3306 check port 9200 inter 12000 rise 3 fall 3
server db173 192.168.1.173:3306 check port 9200 inter 12000 rise 3 fall 3
backend stats-back #开启haproxy的状态页面
mode http
balance roundrobin
stats uri /haproxy/stats #定义访问统计信息的URI
stats auth admin:admin #设置查看统计信息的用户名和密码
3.安装检测脚本（每个节点都需要）
[root@db169 haproxy-1.5.3]# cp /opt/pxc/bin/clustercheck /usr/bin/
[root@db169 haproxy-1.5.3]# cp /opt/pxc/xinetd.d/mysqlchk /etc/xinetd.d/
[root@db169 haproxy-1.5.3]# echo 'mysqlchk 9200/tcp # mysqlchk' >> /etc/services
安装xinetd服务
[root@db169 haproxy-1.5.3]# yum -y install xinetd
[root@db169 haproxy-1.5.3]# /etc/init.d/xinetd restart
停止 xinetd： [失败]
正在启动 xinetd： [确定]
[root@db169 haproxy-1.5.3]# chkconfig --level 2345 xinetd on
创建检查脚本的用户（在任一节点即可）：
grant process on *.* to 'clustercheckuser'@'localhost' identified by 'clustercheckpassword!';
测试检测脚本
[root@db169 haproxy-1.5.3]# clustercheck
HTTP/1.1 200 OK
Content-Type: text/plain
Connection: close
Content-Length: 40
[root@db169 haproxy-1.5.3]# curl -I 127.0.0.1:9200
HTTP/1.1 200 OK
Content-Type: text/plain
Connection: close
Content-Length: 40
要保证状态为200，否则检测不通过，可能是mysql服务不正常，或者环境不对致使haproxy无法使用mysql，
如果不为200，可以手工修改下检测脚本，时期输出到日志，然后排错，比如我的检测就有个错误，一直报503：
[root@db169 examples]# curl -I 192.168.1.172:9200
HTTP/1.1 503 Service Unavailable
Content-Type: text/plain
Connection: close
Content-Length: 44
我修改db172后的检测脚本如下：
[root@db172 data]# cat /usr/bin/clustercheck
#!/bin/bash
#
# Script to make a proxy (ie HAProxy) capable of monitoring Percona XtraDB Cluster nodes properly
#
# Authors:
# Raghavendra Prabhu <raghavendra.prabhu@percona.com>
# Olaf van Zandwijk <olaf.vanzandwijk@nedap.com>
#
# Based on the original script from Unai Rodriguez and Olaf (https://github.com/olafz/percona-clustercheck)
#
# Grant privileges required:
# GRANT PROCESS ON *.* TO 'clustercheckuser'@'localhost' IDENTIFIED BY 'clustercheckpassword!';
if [[ $1 == '-h' || $1 == '--help' ]];then
echo "Usage: $0 <user> <pass> <available_when_donor=0|1> <log_file> <available_when_readonly=0|1> <defaults_extra_file>"
exit
fi
MYSQL_USERNAME="${1-clustercheckuser}"
MYSQL_PASSWORD="${2-clustercheckpassword!}"
AVAILABLE_WHEN_DONOR=${3:-0}
ERR_FILE="${4:-/tmp/mcl2.log}"
AVAILABLE_WHEN_READONLY=${5:-1}
DEFAULTS_EXTRA_FILE=${6:-/etc/my.cnf}
#Timeout exists for instances where mysqld may be hung
TIMEOUT=10
echo "MYSQL_USERNAME : $MYSQL_USERNAME" >>/tmp/mcl.log
echo "MYSQL_PASSWORD : $MYSQL_PASSWORD" >>/tmp/mcl.log
echo "AVAILABLE_WHEN_DONOR : $AVAILABLE_WHEN_DONOR" >>/tmp/mcl.log
echo "ERR_FILE : $ERR_FILE" >>/tmp/mcl.log
echo "AVAILABLE_WHEN_READONLY : $AVAILABLE_WHEN_READONLY" >>/tmp/mcl.log
echo "DEFAULTS_EXTRA_FILE : $DEFAULTS_EXTRA_FILE" >>/tmp/mcl.log
然后再测试：
[root@db172 data]# more /tmp/mcl.log
/usr/bin/clustercheck
/usr/bin/clustercheck
MYSQL_USERNAME : clustercheckuser
MYSQL_PASSWORD : clustercheckpassword!
AVAILABLE_WHEN_DONOR : 0
ERR_FILE : /dev/null
AVAILABLE_WHEN_READONLY : 1
DEFAULTS_EXTRA_FILE : /etc/my.cnf
[root@db172 data]# more /tmp/mcl2.log
/usr/bin/clustercheck: line 44: mysql: command not found
看到问题了，原来是找不到mysql这个可执行文件
[root@db172 data]# which mysql
/opt/pxc/bin/mysql
明明是有的，但这个脚本可能找不到，所以把它复制到/usr/bin下面，在测试就通过了
4.启动haproxy：
[root@db169 ~]# haproxy -f /etc/haproxy/haproxy.cfg
[WARNING] 236/190345 (21350) : parsing [/etc/haproxy/haproxy.cfg:22]: keyword 'redispatch' is deprecated in favor of 'option redispatch', and will not be supported by future versions.
[WARNING] 236/190345 (21350) : parsing [/etc/haproxy/haproxy.cfg:24] : the 'contimeout' directive is now deprecated in favor of 'timeout connect', and will not be supported in future versions.
[WARNING] 236/190345 (21350) : parsing [/etc/haproxy/haproxy.cfg:25] : the 'clitimeout' directive is now deprecated in favor of 'timeout client', and will not be supported in future versions.
[WARNING] 236/190345 (21350) : parsing [/etc/haproxy/haproxy.cfg:26] : the 'srvtimeout' directive is now deprecated in favor of 'timeout server', and will not be supported in future versions.
[ALERT] 236/190345 (21350) : [haproxy.main()] Cannot chroot(/usr/share/haproxy).
报错了，解决方法：
[root@db169 ~]# mkdir /usr/share/haproxy
再次启动：
[root@db169 ~]# haproxy -f /etc/haproxy/haproxy.cfg
[WARNING] 236/190744 (21400) : parsing [/etc/haproxy/haproxy.cfg:22]: keyword 'redispatch' is deprecated in favor of 'option redispatch', and will not be supported by future versions.
[WARNING] 236/190744 (21400) : parsing [/etc/haproxy/haproxy.cfg:24] : the 'contimeout' directive is now deprecated in favor of 'timeout connect', and will not be supported in future versions.
[WARNING] 236/190744 (21400) : parsing [/etc/haproxy/haproxy.cfg:25] : the 'clitimeout' directive is now deprecated in favor of 'timeout client', and will not be supported in future versions.
[WARNING] 236/190744 (21400) : parsing [/etc/haproxy/haproxy.cfg:26] : the 'srvtimeout' directive is now deprecated in favor of 'timeout server', and will not be supported in future versions.
[root@db169 ~]# netstat -anp|grep 3307
tcp 0 0 0.0.0.0:3307 0.0.0.0:* LISTEN 21401/haproxy
已经在3307端口监听了
5.添加开机自启动脚本：
[root@db169 examples]# chmod +x /etc/init.d/haproxy
6.测试
[root@db169 ~]# mysql -p123456 -P3307 -h 192.168.1.169
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 47
Server version: 5.6.19-67.0-25.6-log Percona XtraDB Cluster binary (GPL) 5.6.19-25.6, Revision 824, wsrep_25.6.r4111
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
关闭任意一个节点不影响haproxy的连接。
6.haproxy web端：
http://192.168.1.169:8099/haproxy/stats
输入用户名密码分别为配置文件里的配置即可登录查看负载等情况。
