MySQL高可用新玩法之MGR+Consul

前面的文章有提到过利用consul+mha实现mysql的高可用，以及利用consul+sentinel实现redis的高可用，具体的请查看：http://www.cnblogs.com/gomysql/p/8010552.html。本次给大家带来mysql高可用的新玩法，利用mysql 5.7的mgr+consul实现，至于mgr是什么，有什么优势，如何搭建这里就不说了，大家自己google，我这里就是介绍利用mgr+consul实现高可用及故障自动切换。至于consul是什么可以参考前面的文章。

环境：mgr至少需要3个节点。数据库版本：mysql 5.7.19

我这里使用单主模式。

192.168.100.78
192.168.100.75
192.168.100.74

mgr搭建完成以后查看状态：

[root@localhost][performance_schema]> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-----------------+-------------+--------------+
| CHANNEL_NAME              | MEMBER_ID                            | MEMBER_HOST     | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-----------------+-------------+--------------+
| group_replication_applier | 8e4d93b8-4dd1-11e8-8306-6c92bf7e18e2 | ym_DB_16_100075 |        3306 | ONLINE       |
| group_replication_applier | 9062a0ef-4dd1-11e8-8822-6c92bf744dd6 | ym_DB_15_100074 |        3306 | ONLINE       |
| group_replication_applier | 9a7e7cd5-4dd1-11e8-b28c-6c92bf7e0d2e | ym_DB_19_100078 |        3306 | ONLINE       |
+---------------------------+--------------------------------------+-----------------+-------------+--------------+

查看主节点是哪个（我的环境是单主，官方也是推荐使用单主）

[root@localhost][performance_schema]> select * from  performance_schema.replication_group_members where member_id =(select variable_value from performance_schema.global_status WHERE VARIABLE_NAME= 'group_replication_primary_member');
+---------------------------+--------------------------------------+-----------------+-------------+--------------+
| CHANNEL_NAME              | MEMBER_ID                            | MEMBER_HOST     | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-----------------+-------------+--------------+
| group_replication_applier | 8e4d93b8-4dd1-11e8-8306-6c92bf7e18e2 | ym_DB_16_100075 |        3306 | ONLINE       |
+---------------------------+--------------------------------------+-----------------+-------------+--------------+
1 row in set (0.00 sec)

可以看见我目前的主节点是100.75。到此mgr环境ok。下面到部署consul，前面的文章提到过，需要服务发现的机器都需要安装consul客户端，也就是3台服务器都需要安装。其中涉及到2个检查脚本（脚本不够完善，比如复制延时是否进行注册）。
主节点检查脚本：

#!/bin/bash
port=$
user="root"
passwod=""

comm="/usr/local/mysql/bin/mysql -u$user -h 127.0.0.1 -P $port -p$passwod"
value=`$comm -Nse "select 1"`
primary_member=`$comm -Nse "select variable_value from performance_schema.global_status WHERE VARIABLE_NAME= 'group_replication_primary_member'"`
server_uuid=`$comm -Nse "select variable_value from performance_schema.global_variables where VARIABLE_NAME='server_uuid';"`

# 判断mysql是否存活
if [ -z $value ]
then
   echo "mysql $port is down....."
   exit
fi

# 判断节点状态
node_state=`$comm -Nse "select MEMBER_STATE from performance_schema.replication_group_members where MEMBER_ID='$server_uuid'"`
if [ $node_state != "ONLINE" ]
then
   echo "MySQL $port state is not online...."
   exit
fi

# 判断是不是主节点
if [[ $server_uuid == $primary_member ]]
then
   echo "MySQL $port  Instance is master ........"
   exit
else
   echo "MySQL $port  Instance is slave ........"
   exit
fi

从节点检查脚本：

#!/bin/bash
port=$
user="root"
passwod=""

comm="/usr/local/mysql/bin/mysql -u$user -h 127.0.0.1 -P $port -p$passwod"
value=`$comm -Nse "select 1"`
primary_member=`$comm -Nse "select variable_value from performance_schema.global_status WHERE VARIABLE_NAME= 'group_replication_primary_member'"`
server_uuid=`$comm -Nse "select variable_value from performance_schema.global_variables where VARIABLE_NAME='server_uuid';"`

# 判断mysql是否存活
if [ -z $value ]
then
   echo "mysql $port is down....."
   exit
fi

# 判断节点状态
node_state=`$comm -Nse "select MEMBER_STATE from performance_schema.replication_group_members where MEMBER_ID='$server_uuid'"`
if [ $node_state != "ONLINE" ]
then
   echo "MySQL $port state is not online...."
   exit
fi

# 判断是不是主节点
if [[ $server_uuid != $primary_member ]]
then
   echo "MySQL $port  Instance is slave ........"
   exit
else
   node_num=`$comm -Nse "select count(*) from  performance_schema.replication_group_members"`
   # 判断如果没有任何从节点，主节点也注册从角色服务。
   if [ $node_num -eq  ]
   then
       echo "MySQL $port  Instance is slave ........"
       exit
   else
       echo "MySQL $port  Instance is master ........"
       exit
   fi
fi

其中一台服务器的consul配置文件，有master和slave，如下：

[root@ym_DB_16_100075 conf]# cat payment--mydb-ser.json
{
  "services": [
    {
      "name": "payment-3306-mydb-ser",
      "tags": [
        "充值-3306"
      ],
      "address": "192.168.100.75",
      "port": ,
      "checks": [
        {
          "script": "/usr/local/consul/shell/check_mysql_mgr_master.sh 3306",
          "interval": "15s"
        }
      ]
    }
  ]
}

[root@ym_DB_16_100075 conf]# cat r-payment--mydb-ser.json
{
  "services": [
    {
      "name": "r-payment-3306-mydb-ser",
      "tags": [
        "充值-3306"
      ],
      "address": "192.168.100.75",
      "port": ,
      "checks": [
        {
          "script": "/usr/local/consul/shell/check_mysql_mgr_slave.sh 3306",
          "interval": "15s"
        }
      ]
    }
  ]
}

其他两台服务器配置文件一样，只是"address"改成对应服务器的地址就完事。启动consul。ping其中一个域名，比如：payment-3306-mydb-ser.service.consul，那么返回的是主节点的ip，因为这个域名是写的。如果ping r-payment-3306-mydb-ser.service.consul，那么返回的是另外两个从节点的ip。

从上面可以看到写的域名解析到的主节点，读的域名解析到了2个从节点，从节点可以实现负载均衡的效果。

故障测试：

1. 把主节点停掉，查看写的域名payment-3306-mydb-ser.service.consul会解析到哪里。

[root@localhost][(none)]> select * from  performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-----------------+-------------+--------------+
| CHANNEL_NAME              | MEMBER_ID                            | MEMBER_HOST     | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-----------------+-------------+--------------+
| group_replication_applier | 9062a0ef-4dd1-11e8-8822-6c92bf744dd6 | ym_DB_15_100074 |        3306 | ONLINE       |
| group_replication_applier | 9a7e7cd5-4dd1-11e8-b28c-6c92bf7e0d2e | ym_DB_19_100078 |        3306 | ONLINE       |
+---------------------------+--------------------------------------+-----------------+-------------+--------------+
2 rows in set (0.00 sec)

停掉以后发现之前的100.75主节点已经被移除，已经自动选出新的节点：

[root@localhost][(none)]> select * from  performance_schema.replication_group_members where member_id =(select variable_value from performance_schema.global_status WHERE VARIABLE_NAME= 'group_replication_primary_member');
+---------------------------+--------------------------------------+-----------------+-------------+--------------+
| CHANNEL_NAME              | MEMBER_ID                            | MEMBER_HOST     | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-----------------+-------------+--------------+
| group_replication_applier | 9062a0ef-4dd1-11e8-8822-6c92bf744dd6 | ym_DB_15_100074 |        3306 | ONLINE       |
+---------------------------+--------------------------------------+-----------------+-------------+--------------+

可以看到现在的主节点已经是100.74，那么我们看看域名payment-3306-mydb-ser.service.consul解析到哪里：

可以看到没有问题，正常。再看看读域名：r-payment-3306-mydb-ser.service.consul

可以看到一切正常。后续检查脚本可以判断是否延时，如果延时就不注册服务。