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 30sstats 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
#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

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