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=$1
user="root"
passwod="123"

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 2
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 2
fi


# 判断是不是主节点
if [[ $server_uuid == $primary_member ]]
then
   echo "MySQL $port  Instance is master ........"
   exit 0
else
   echo "MySQL $port  Instance is slave ........"
   exit 2
fi

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