MySQL从库集群方案之HAProxy篇
HAProxy反向代理服务器支持双机热备支持虚拟主机，其配置简单，拥有非常不错的服务器健康检查功能。当其代理的后端服务器出现故障，HAProxy会自动将该服务器摘除，故障恢复后再自动将该服务器加入。这里有两台HAProxy机器，分别安装keepalived，组成热备形式。作用：当一台有问题，另一台可以在1秒内接管。
xinetd服务的作用是检测端口，本文中使用8890端口。HAProxy用http协议检测这个端口是否正常。
MySQL同步状态脚本，是放在从库本地，由xinetd服务来激活脚本，正常就会输出200状态码给HAProxy，证明从库正常；否则，就剔除。（这里就可以加上短信报警了）

系统架构图

使用软件
HAProxy 1.4.16
Keepalived 1.1.20
Xinetd 2.3.14
MySQL 同步状态脚本 0.2

一、系统约定
系统环境
OS:CentOS 5.6 x86_64
MASTER:192.168.1.65
BACKUP:192.168.1.66
VIP:192.168.1.67
serivce Port:3306
工作流程
准备工作：应用配置好slave的VIP 192.168.1.67 端口3306
(1)应用服务器
(2)连接HAProxy的vip 192.168.1.67:3306，根据算法，分配到一台slave。
(3)检测slave的8890端口是否返回http 200状态码。
(4)返回200 状态码，HAProxy 返回正常，继续服务。
(5)返回503，剔除该slave，并将mysql请求转发到另外一台slave。
(6)有问题的slave，发送短信报警，相关人员检查。

二、Keepalived 1.1.20的安装于配置
#cd /var/tmp/
#wget http://www.keepalived.org/software/keepalived-1.1.20.tar.gz
#tar zxvf keepalived-1.1.20.tar.gz
#cd keepalived-1.1.20
#./configure –prefix=/usr
#make && make install
#cp /usr/etc/rc.d/init.d/keepalived /etc/rc.d/init.d/
#cp /usr/etc/sysconfig/keepalived /etc/sysconfig/
#mkdir /etc/keepalived

vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
notification_email {
[email]coralzd@gmail.com[/email]
}
notification_email_from [email]coralzd@gmail.com[/email]
smtp_server 192.168.1.1
smtp_connect_timeout 30
router_id LVS_DEVEL
}
vrrp_script chk_HAProxy {
script "killall -0 HAProxy"
interval 2
weight 2
}
vrrp_instance VI_1 {
state MASTER
interface eth0
virtual_router_id 50
priority 150
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
track_interface {
eth0

}
virtual_ipaddress {
192.168.1.67

}
track_script {
chk_HAProxy
}
}

三、HAProxy 1.4.16的安装与配置
#cd /var/tmp/
#wget http://HAProxy.1wt.eu/download/1.4/src/HAProxy-1.4.16.tar.gz
#tar -zxvf HAProxy-1.4.16.tar.gz
#cd HAProxy-1.4.16
#make install
#mkdir -p /usr/local/HAProxy/etc
#mkdir -p /usr/local/HAProxy/sbin
#cp examples/HAProxy.cfg /usr/local/HAProxy/etc
#ln -s /usr/local/sbin/HAProxy /usr/local/HAProxy/sbin/HAProxy
#mkdir /usr/share/HAProxy
/etc/HAProxy/HAProxy.cfg
global
log 127.0.0.1 local1 notice
maxconn 4096
chroot /usr/share/HAProxy
uid 99
gid 99
daemon
#debug
#quiet
defaults
log global
mode http
#option httplog
option dontlognull
retries 3
option redispatch
maxconn 2000
contimeout 5000
clitimeout 50000
srvtimeout 50000
listen DZW_MYSQL_SLAVE 192.168.1.67:3306
#cookie SERVERID rewrite
mode tcp
maxconn 200
balance roundrobin
option httpchk OPTIONS * HTTP/1.1\r\nHost:\ www
server mysql_192_168_1_23 192.168.1.23:3306 check port 8890 inter 5s rise 2 fall 3
server mysql_192_168_1_24 192.168.1.24:3306 check port 8890 inter 5s rise 2 fall 3

srvtimeout 20000
listen admin_status
mode http
bind 192.168.1.65:8899
option httplog
log global
stats enable
stats refresh 10s
stats hide-version
stats realm Haproxy\ Statistics
stats uri /admin-status
stats auth admin:123456
stats admin if TRUE

HAProxy 启动脚本
/etc/init.d/HAProxy
#!/bin/sh
#
# chkconfig: - 85 15
# description: HA-Proxy is a TCP/HTTP reverse proxy which is particularly suited \
# for high availability environments.
# processname: HAProxy
# config: /etc/HAProxy/HAProxy.cfg
# pidfile: /var/run/HAProxy.pid
# Script Author: Simon Matter <[email]simon.matter@invoca.ch[/email]>
# Version: 2004060600
# Source function library.
if [ -f /etc/init.d/functions ]; then
. /etc/init.d/functions
elif [ -f /etc/rc.d/init.d/functions ] ; then
. /etc/rc.d/init.d/functions
else
exit 0
fi
# Source networking configuration.
. /etc/sysconfig/network
# Check that networking is up.
[ ${NETWORKING} = "no" ] && exit 0
# This is our service name
BASENAME=HAProxy
if [ -L ___FCKpd___2 ]; then
BASENAME=`find ___FCKpd___2 -name $BASENAME -printf %l`
BASENAME=`basename $BASENAME`
fi
[ -f /etc/$BASENAME/$BASENAME.cfg ] || exit 1
RETVAL=0
start() {
/usr/sbin/$BASENAME -c -q -f /etc/$BASENAME/$BASENAME.cfg
if [ $? -ne 0 ]; then
echo "Errors found in configuration file, check it with '$BASENAME check'."
return 1
fi
echo -n "Starting $BASENAME: "
daemon /usr/sbin/$BASENAME -D -f /etc/$BASENAME/$BASENAME.cfg -p /var/run/$BASENAME.pid
RETVAL=$?
echo
[ $RETVAL -eq 0 ] && touch /var/lock/subsys/$BASENAME
return $RETVAL
}
stop() {
echo -n "Shutting down $BASENAME: "
killproc $BASENAME -USR1
RETVAL=$?
echo
[ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/$BASENAME
[ $RETVAL -eq 0 ] && rm -f /var/run/$BASENAME.pid
return $RETVAL
}
restart() {
/usr/sbin/$BASENAME -c -q -f /etc/$BASENAME/$BASENAME.cfg
if [ $? -ne 0 ]; then
echo "Errors found in configuration file, check it with '$BASENAME check'."
return 1
fi
stop
start
}
reload() {
/usr/sbin/$BASENAME -c -q -f /etc/$BASENAME/$BASENAME.cfg
if [ $? -ne 0 ]; then
echo "Errors found in configuration file, check it with '$BASENAME check'."
return 1
fi
/usr/sbin/$BASENAME -D -f /etc/$BASENAME/$BASENAME.cfg -p /var/run/$BASENAME.pid -sf $(cat /var/run/$BASENAME.pid)
}
check() {
/usr/sbin/$BASENAME -c -q -V -f /etc/$BASENAME/$BASENAME.cfg
}
rhstatus() {
status $BASENAME
}
condrestart() {
[ -e /var/lock/subsys/$BASENAME ] && restart || :
}
# See how we were called.
case "$1" in
start)
start
;;
stop)
stop
;;
restart)
restart
;;
reload)
reload
;;
condrestart)
condrestart
;;
status)
rhstatus
;;
check)
check
;;
*)
echo ___FCKpd___2quot;Usage: $BASENAME {start|stop|restart|reload|condrestart|status|check}"
exit 1
esac
exit $?
chkconfig --add HAProxy
chkconfig HAProxy on
service HAProxy start

四、xinetd安装和配置
yum install -y xinetd
vim /etc/xinetd.d/mysql_status.sh
service mysqlrep_status
{
flags = REUSE
socket_type = stream
port = 8890
wait = no
user = nobody
server = /usr/local/bin/mysqlrep_status.sh
log_on_failure += USERID
disable = no

}

重启xinetd
service xinetd restart

MySQL同步检测脚本（脚本检测同步sql和IO进程是否都为真，以及select是否达到20个进程以上）
#!/bin/bash
#
# /usr/local/bin/mysqlchk_status.sh
#
# This script checks if a mysql server is healthy running on localhost. It will
# return:
#
# "HTTP/1.x 200 OK\r" (if mysql is running smoothly)
#
# – OR –
#
# "HTTP/1.x 503 Internal Server Error\r" (else)
#
MYSQL_HOST="localhost"
MYSQL_PORT="3306"
MYSQL_USERNAME="repdb63"
MYSQL_PASSWORD="mylqs9eyex7s"
#
# We perform a simple query that should return a few results
#/usr/local/mysql/bin/mysql -hlocalhost –urepdb63 –pmylqs9eyex7s -e "show slave status\G;" > /tmp/rep.txt
mysql -urepdb63 -pmylqs9eyex7s -e "show full processlist;" >/tmp/processlist.txt
mysql -urepdb63 -pmylqs9eyex7s -e "show slave status\G;" >/tmp/rep.txt
iostat=`grep "Slave_IO_Running" /tmp/rep.txt |awk '{print $2}'`
sqlstat=`grep "Slave_SQL_Running" /tmp/rep.txt |awk '{print $2}'`
result=$(cat /tmp/processlist.txt|wc -l)
#echo iostat:$iostat and sqlstat:$sqlstat
# if slave_IO_Running and Slave_sql_Running ok,then return 200 code
if [ "$result" -lt "20" ] && [ "$iostat" = "Yes" ] && [ "$sqlstat" = "Yes" ];
then
# mysql is fine, return http 200
/bin/echo -e "HTTP/1.1 200 OK\r\n"

else
# mysql is down, return http 503
/bin/echo -e "HTTP/1.1 503 Service Unavailable\r\n"
fi
注意：在mysql slave另行建立一个具有process和slave_client权限的账号。