在实际项目中，Mycat 服务也需要考虑高可用性，如果 Mycat 所在服务器出现宕机，或 Mycat 服务故障，需要有备机提供服务，需要考虑 Mycat 集群。

6.1、高可用方案

我们可以使用 HAProxy + Keepalived配合两台Mycat搭起Mycat集群，实现高可用性。HAProxy实现了 MyCat 多节点的集群高可用和负载均衡， 而 HAProxy 自身的高可用则可以通过Keepalived 来实现。

6.2、安装置 配置 HAProxy

1、 安装HAProxy；

#1准备好HAProxy安装包，传到/opt目录下
#2解压到/usr/local/src
tar -zxvf haproxy-1.5.18.tar.gz -C /usr/local/src
#3进入解压后的目录，查看内核版本，进行编译
cd /usr/local/src/haproxy-1.5.18
uname -r
make TARGET=linux310 PREFIX=/usr/local/haproxy ARCH=x86_64
# ARGET=linux310，内核版本，使用uname -r查看内核，如：3.10.0-514.el7，此时该参数就为linux310；
#ARCH=x86_64，系统位数；
#PREFIX=/usr/local/haprpxy/usr/local/haprpxy，为haprpxy安装路径。
#4编译完成后，进行安装
make install PREFIX=/usr/local/haproxy
#5安装完成后，创建目录、创建HAProxy配置文件
mkdir -p /usr/data/haproxy/
vim /usr/local/haproxy/haproxy.conf
#6向配置文件中插入以下配置信息,并保存
global
log 127.0.0.1 local0
#log 127.0.0.1 local1 notice
#log loghost local0 info
maxconn 4096
chroot /usr/local/haproxy
pidfile /usr/data/haproxy/haproxy.pid
uid 99
gid 99
daemon
#debug
#quiet

defaults
log  global
mode tcp
option abortonclose
option redispatch
retries 3
maxconn 2000
timeout connect 5000
timeout client 50000
timeout server 50000
listen proxy_status
bind :48066
mode tcp
balance roundrobin
server mycat_1 192.168.140.128:8066 check inter 10s
server mycat_2 192.168.140.127:8066 check inter 10s
frontend admin_stats
bind :7777
mode http
stats enable
option httplog
maxconn 10
stats refresh 30s
stats uri /admin
stats auth admin:123123
stats hide-version
stats admin if TRUE

2、 启动验证；

#1启动HAProxy
/usr/local/haproxy/sbin/haproxy -f /usr/local/haproxy/haproxy.conf
#2查看HAProxy进程
ps -ef|grep haproxy
#3打开浏览器访问
http://192.168.140.125:7777/admin
#在弹出框输入用户名：admin密码：123123
#如果Mycat主备机均已启动，则可以看到如下图
 
#4验证负载均衡，通过HAProxy访问Mycat
mysql -umycat -p123456 -h 192.168.140. 126 -P 48066

6.3、配置 Keepalived

1、 安装Keepalived；

# 1准备好Keepalived安装包，传到/opt目录下
wget http://www.keepalived.org/software/keepalived-1.4.2.tar.gz
# 2解压到/usr/local/src
tar -zxvf keepalived-1.4.2.tar.gz -C /usr/local/src
# 3安装依赖插件
yum install -y gcc openssl-devel popt-devel
# 3进入解压后的目录，进行配置，进行编译
cd /usr/local/src/keepalived-1.4.2
./configure --prefix=/usr/local/keepalived
# 4进行编译，完成后进行安装
make && make install
# 5运行前配置
cp /usr/local/src/keepalived-1.4.2/keepalived/etc/init.d/keepalived /etc/init.d/
mkdir /etc/keepalived
cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/
cp /usr/local/src/keepalived-1.4.2/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
cp /usr/local/keepalived/sbin/keepalived /usr/sbin/
# 6修改配置文件
vim /etc/keepalived/keepalived.conf
#修改内容如下
! Configuration File for keepalived
global_defs {
  notification_email {
      xlcocoon@foxmail.com
  }
  notification_email_from keepalived@showjoy.com
  smtp_server 127.0.0.1
  smtp_connect_timeout 30
  router_id LVS_DEVEL
  vrrp_skip_check_adv_addr
  vrrp_garp_interval 0
  vrrp_gna_interval 0
}
vrrp_instance VI_1 {
 主机配MASTER，备机配BACKUP
  state MASTER
 所在机器网卡
  interface ens33
  virtual_router_id 51
 数值越大优先级越高
  priority 100
  advert_int 1
  authentication {
    auth_type PASS
    auth_pass 1111
  }
  virtual_ipaddress {
 虚拟IP
    192.168.140.200
    }
}
virtual_server 192.168.140.200 48066 {
  delay_loop 6
  lb_algo rr
  lb_kind NAT
  persistence_timeout 50
  protocol TCP
  real_server 192.168.140.125 48066 {
  weight 1
      TCP_CHECK {
        connect_timeout 3
        retry 3 
        delay_before_retry 3
      }
  }
  real_server 192.168.140.126 48600 {
      weight 1
    TCP_CHECK {
      connect_timeout 3
      nb_get_retry 3
      delay_before_retry 3
    }
    }
}

2、 启动验证；

#1启动Keepalived
service keepalived start
#2登录验证
mysql -umycat -p123456 -h 192.168.140.200 -P 48066

6.4 、测试高可用

1、测试步骤
#1关闭mycat
#2通过虚拟ip查询数据
mysql -umycat -p123456 -h 192.168.140.200 -P 48066