MySQL高可用新玩法之MGR+Consul
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/bashport=$user="root"passwod="" comm="/usr/local/mysql/bin/mysql -u$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 $port is down....." exitfi # 判断节点状态node_state=`$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...." exitfi # 判断是不是主节点if [[ $server_uuid == $primary_member ]]then echo "MySQL $port Instance is master ........" exitelse echo "MySQL $port Instance is slave ........" exitfi从节点检查脚本：
#!/bin/bashport=$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 $port is down....." exitfi # 判断节点状态node_state=`$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...." exitfi # 判断是不是主节点if [[ $server_uuid != $primary_member ]]then echo "MySQL $port Instance is slave ........" exitelse node_num=`$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 fifi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。
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