企业级高可用Web架构之HAProxy+Keepalived
细数下来，算是东莞的项目的话，HAProxy+Keepalived我差不多也有三套在线上跑了，另外，这套Web方案也是我的一拍网的备份方案之一，目前也在测试，如果速度和稳定性够强劲的话，我也考虑将LVS+Keepalived换成HAProxy+Keepalived，关于HAProxy的语法和安装步骤请参考我的专题系列文章http://network.iyunv.com/art/201101/241997.htm，另外，此篇文章跟刘天斯的不一样，我主要用其作为Web级别的负载均衡（七层应用）。一、线上跑的HAProxy配置文件，代码如下：
global
log 127.0.0.1 local0
maxconn 65535
chroot /usr/local/haproxy
uid 99
gid 99
daemon
nbproc 8
pidfile /usr/local/haproxy/haproxy.pid
debug
defaults
log 127.0.0.1 local3
mode http
option httplog
option httpclose
option dontlognull
option forwardfor
option redispatch
retries 2
maxconn 2000
balance source
stats uri /web-status
contimeout 5000
clitimeout 50000
srvtimeout 50000
listen www.1paituan.com
bind *:80
mode http
option httplog
log global
option httpchk HEAD /index.jsp HTTP/1.0
server web1 203.93.236.147:80 weight 5 check inter 2000 rise 2 fall 3
server web2 203.93.236.146:80 weight 3 check inter 2000 rise 2 fall 3
二、HAProxy的启动、关闭和重启脚本，代码如下：
#!/bin/sh
# chkconfig 35 on
# description: HAProxy is a TCP/HTTP reverse proxy which is particularly suited for high availability environments.
# 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
[ -f /usr/local/haproxy/conf/haproxy.cfg ] || exit 1
RETVAL=0
start() {
/usr/local/haproxy/sbin/haproxy -c -q -f /usr/local/haproxy/conf/haproxy.cfg
if [ $? -ne 0 ]; then
echo "Errors found in configuration file."
return 1
fi
echo -n "Starting HAproxy: "
daemon /usr/local/haproxy/sbin/haproxy -D -f /usr/local/haproxy/conf/haproxy.cfg -p /var/run/haproxy.pid
RETVAL=$?
echo
[ $RETVAL -eq 0 ] && touch /var/lock/subsys/haproxy
return $RETVAL
}
stop() {
echo -n "Shutting down HAproxy: "
killproc haproxy -USR1
RETVAL=$?
echo
[ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/haproxy
[ $RETVAL -eq 0 ] && rm -f /var/run/haproxy.pid
return $RETVAL
}
restart() {
/usr/local/haproxy/sbin/haproxy -c -q -f /usr/local/haproxy/conf/haproxy.cfg
if [ $? -ne 0 ]; then
echo "Errors found in configuration file, check it with 'haproxy check'."
return 1
fi
stop
start
}
check() {
/usr/local/haproxy/sbin/haproxy -c -q -V -f /usr/local/haproxy/conf/haproxy.cfg
}
rhstatus() {
status haproxy
}
condrestart() {
[ -e /var/lock/subsys/haproxy ] && restart || :
}
# See how we were called.
case "$1" in
start)
start
;;
stop)
stop
;;
restart)
restart
;;
reload)
restart
;;
condrestart)
condrestart
;;
status)
rhstatus
;;
check)
check
;;
*)
echo $"Usage: haproxy {start|stop|restart|reload|condrestart|status|check}"
RETVAL=1
esac
exit $RETVAL
三、HAProxy的监控脚本我没有做，这个实施起来也简单，我们可以用curl -s --head http://www.1paituan.com/index.jsp | awk '/HTTP/ {print $2}'的方法，判断是否返回了正常的200代码。
四、加上日志支持，代码如下：
#vim /etc/syslog.conf
添加：
local3.* /var/log/haproxy.log
local0.* /var/log/haproxy.log
#vim /etc/sysconfig/syslog
修改：
SYSLOGD_OPTIONS="-r -m 0"
service syslog restart
五、大家需要注意的几个地方是：
1)HAProyx采用的是balance source机制，它跟Nginx的ip_hash机制原理类似，是让客户机访问时始终访问后端的某一台真实的web服务器，这样让session就固定下来了；
2)option httpchk HEAD /index.jsp HTTP/1.0 是网页监控，如果HAProxy检测不到Web的根目录下没有index.jsp，就会产生503报错。
3)有网友说HAProxy必须采用listen 203.93.236.141:80这样类似的格式，这样其实不好，做集群时会导致从机启动不了，我们可以用bind *:80的方式代替。
4)HAProxy的并发监控和日志收集分析是下一步考虑的事情。
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