应用场景:
网站流量不高，压力不大，但是对服务器的可靠性要求极其高，例如实时在线OA系统，*部门网站系统，医院实时报医系统，*局在线报案系统，股市后台网站系统等等，他们的压力不是很大，但是对可靠性要求是非常高的.
特性:
通过vip飘移，实现故障切换。只能支持2个节点，不支持更多节点管理；容易发生脑裂.
优点:
数据同步非常简单，不像负载均衡对数据一致性要求非常高，实现起来相对复杂维护也颇为不便，双机热备用rsync就可以实现了操作和维护非常简单.
缺点:
脑裂无法解决，需要引入第三方仲裁节点，有一个节点空闲.
前提:
存在互为主从的mysql实例(A:192.168.255.134 B:192.168.255.135)A实例:192.168.255.134
1.首先安装keepalived
a.源码安装
b.yum安装(yum install keepalived -y)
2.安装MySQL-python(检测mysql是否启动是基于python的)
yum install MySQL-python
3.修改keepalived.conf(/etc/keepalived/keepalived.conf)
vrrp_script vs_mysql_134 {
script "/home/keepalived/checkMySQL.py -h 192.168.255.134 -P 3306" //监控脚本
interval 60 // 监控时间
}
vrrp_instance VI_134 {
state BACKUP
nopreempt
interface eth0 //绑定虚拟IP的网络接口
virtual_router_id 134 //VRRP组名，两个节点的设置必须一样，以指明各个节点属于同一VRRP组
priority 100
advert_int 5
authentication {
auth_type PASS // 加密
auth_pass 1111 // 加密的密码，两台服务器一定要一样，不然会出错
}
track_script {
vs_mysql_134 // 执行监控的服务
}
virtual_ipaddress {
192.168.255.150 //VIP 地址
}
}
4.创建/home/keepalived/checkMySQL.py文件，内容如下：
#!/usr/bin/python
#coding: utf-8
#
import sys
import os
import getopt
import MySQLdb
import logging
dbhost='localhost'
dbport=3306
dbuser='monitor'
dbpassword='m0n1tor'
def checkMySQL():
global dbhost
global dbport
global dbuser
global dbpassword
shortargs='h:P:'
opts, args=getopt.getopt(sys.argv[1:],shortargs)
for opt, value in opts:
if opt=='-h':
dbhost=value
elif opt=='-P':
dbport=value
#print "host : %s, port: %d, user: %s, password: %s" % (dbhost, int(dbport), dbuser, dbpassword)
db = instanceMySQL(dbhost, dbport, dbuser, dbpassword)
st = db.ishaveMySQL()
#if ( db.connect() != 0 ):
# return 1
#db.disconnect()
return st
class instanceMySQL:
conn = None
def __init__(self, host=None,port=None, user=None, passwd=None):
self.dbhost= host
self.dbport = int(port)
self.dbuser = user
self.dbpassword = passwd
def ishaveMySQL(self):
cmd="ps -ef | egrep -i \"mysqld\" | egrep -iv \"mysqld_safe\" | grep -v grep | wc -l"
mysqldNum = os.popen(cmd).read()
cmd ="netstat -tunlp | grep \":%s\" | wc -l" % self.dbport
mysqlPortNum= os.popen(cmd).read()
#print mysqldNum, mysqlPortNum
if ( int(mysqldNum) <= 0):
print "error"
return 1
if ( int(mysqldNum) > 0 and mysqlPortNum <= 0):
return 1
return 0
def connect(self):
# print "in db conn"
# print "host : %s, port: %d, user: %s, password: %s" % (self.dbhost, self.dbport, self.dbuser, self.dbpassword)
try:
self.conn=MySQLdb.connect(host="%s"%self.dbhost, port=self.dbport,user="%s"%dbuser, passwd="%s"%self.dbpassword)
except Exception, e:
# print " Error"
print e
return 1
return 0
def disconnect(self):
if (self.conn):
self.conn.close()
self.conn = None
if __name__== "__main__":
st=checkMySQL()
sys.exit(st)
5. 将步骤4中创建的文件赋予可自行的权限
chmod 755 /home/keepalived/checkMySQL.py
6.在mysql创建一个监控用户：
GRANT REPLICATION CLIENT ON *.* TO 'monitor'@'%' IDENTIFIED BY 'm0n1tor';
7.启动keepalived，提示如下(tail -f /var/log/messages):
则表示成功。
B实例:192.168.255.135
1.同实例A
2.同实例A
3.修改keepalived.conf(/etc/keepalived/keepalived.conf)
vrrp_script vs_mysql_135 {
script "/home/keepalived/checkMySQL.py -h 192.168.255.135 -P 3306"
interval 60
}
vrrp_instance VI_135 {
state BACKUP
nopreempt
interface eth0
virtual_router_id 134
priority 100
advert_int 5
authentication {
auth_type PASS
auth_pass 1111
}
track_script {
vs_mysql_135
}
virtual_ipaddress {
192.168.255.150
}
}
4.同实例A
5.同实例A
6.同实例A
7.启动keepalived，提示如下(tail -f /var/log/messages):
则表示成功
