192.168.205.37: as MHA server
192.168.205.47: as Master server
192.168.205.57: as Slave1 server
192.168.205.67: as Slave2 server

OS: centos 7 1810 with mini install
mariadb-server 5.5.60
mha4mysql-manager-0.56-0.el6.noarch.rpm
mha4mysql-node-0.56-0.el6.noarch.rpm

MHA使用perl脚本写的程序，当主节点down时如果从节点复制没有完成时，当他成为主节点后，它需要尝试将主节点的二进制日志复制到新的主节点，从而保证数据的完整性，所以它需要sshkey验证。我们使用一台做为管理节点，其中三个为数据库节点，一主两从，模拟主节点down机，看从是如何被提升为主节点的。

安装mariadb使用如下脚本：

[root@master data]#cat maridb_yum.sh #!/bin/bashID=`ip a show dev eth0 | sed -r '3!d;s@(.*inet)(.*)(/.*)@\2@' | cut -d. -f4`rpm -q mariadb-server ||yum install -y mariadb-server[ -d /data/mysql ] || mkdir -p /data/mysql[ -d /data/logs ] || mkdir -p /data/logschown mysql:mysql /data/{mysql,logs}sed -i 's@datadir=/var/lib/mysql@datadir=/data/mysql@' /etc/my.cnfgrep "log-bin" /etc/my.cnf || sed -i '/\[mysqld\]/a log-bin=/data/logs/bin' /etc/my.cnfgrep "innodb_file_per_table" /etc/my.cnf || sed -i '/\[mysqld\]/a innodb_file_per_table = on' /etc/my.cnfgrep "skip_name_resolve" /etc/my.cnf || sed -i '/\[mysqld\]/a skip_name_resolve = on' /etc/my.cnfgrep "server-id" /etc/my.cnf || sed -i "/\[mysqld\]/a server-id=$ID" /etc/my.cnfservice mariadb restart

修改两个从节点的配置文件

[root@slave1 data]#vi /etc/my.cnf[mysqld]read_only relay_log_purge=0 #不删除中继日志

建立主节点的复制位置和帐号

MariaDB [(none)]> show master logs;+------------+-----------+| Log_name | File_size |+------------+-----------+| bin.000001 | 30373 || bin.000002 | 1038814 || bin.000003 | 245 |+------------+-----------+3 rows in set (0.00 sec)MariaDB [(none)]> grant replication slave on *.* to repluser@'192.168.205.%' identified by 'centos';Query OK, 0 rows affected (0.00 sec)MariaDB [(none)]> grant all on *.* to mhauser@'192.168.205.%' identified by 'centos'; Query OK, 0 rows affected (0.00 sec)

配置从节点的change master to并启动线程

MariaDB [(none)]> CHANGE MASTER TO-> MASTER_HOST='192.168.205.47',-> MASTER_USER='repluser',-> MASTER_PASSWORD='centos',-> MASTER_PORT=3306,-> MASTER_LOG_FILE='bin.000003',-> MASTER_LOG_POS=245;Query OK, 0 rows affected (0.01 sec)MariaDB [(none)]> start slave;Query OK, 0 rows affected (0.00 sec)MariaDB [(none)]> show slave status\G*************************** 1. row *************************** Slave_IO_State: Waiting for master to send eventMaster_Host: 192.168.205.47Master_User: repluserMaster_Port: 3306Connect_Retry: 60Master_Log_File: bin.000003Read_Master_Log_Pos: 401 Relay_Log_File: mariadb-relay-bin.000002Relay_Log_Pos: 679Relay_Master_Log_File: bin.000003 Slave_IO_Running: YesSlave_SQL_Running: Yes

MHA实现安装包，mha依赖epel源，我们要把epel起用

[root@MHA ~]#yum install mha4mysql-manager-0.56-0.el6.noarch.rpm mha4mysql-node-0.56-0.el6.noarch.rpm 

在所有的sql节点上安装node包

[root@master ~]#yum install mha4mysql-node-0.56-0.el6.noarch.rpm [root@slave1 data]#yum install mha4mysql-node-0.56-0.el6.noarch.rpm [root@slave2 data]#yum install mha4mysql-node-0.56-0.el6.noarch.rpm 

配置ssh key 验证

[root@MHA ~]#ssh-keygen [root@MHA ~]#ssh-copy-id 192.168.205.37[root@MHA ~]#cat .ssh/authorized_keys [root@MHA ~]#scp -r .ssh 192.168.205.47:/root/[root@MHA ~]#scp -r .ssh 192.168.205.57:/root/[root@MHA ~]#scp -r .ssh 192.168.205.67:/root/

生成配置MHA文件

[root@MHA ~]#mkdir /etc/mha[root@MHA ~]#vim /etc/mha/app1.cnf[server default]master_binlog_dir=/data/logs/ user=mhauserpassword=centosmanager_workdir=/data/mastermha/app1/manager_log=/data/mastermha/app1/manager.logremote_workdir=/data/mastermha/app1/ssh_user=rootrepl_user=repluserrepl_password=centosping_interval=1[server1]hostname=192.168.205.47candidate_master=1[server2]hostname=192.168.205.57[server3]hostname=192.168.205.67candidate_master=1

启动之前进行检查ssh，repl复制是否准备好

[root@MHA ~]#masterha_check_ssh --conf=/etc/mha/app1.cnf[root@MHA ~]#masterha_check_repl --conf=/etc/mha/app1.cnf

起动进程，此进程前台运行，当主节点失败时切换完成后它会终止，所以要想持续要重启进程

[root@MHA ~]#masterha_manager --conf=/etc/mha/app1.cnfMon Aug 12 23:33:22 2019 - [warning] Global configuration file /etc/masterha_default.cnf not found. Skipping.Mon Aug 12 23:33:22 2019 - [info] Reading application default configuration from /etc/mha/app1.cnf..Mon Aug 12 23:33:22 2019 - [info] Reading server configuration from /etc/mha/app1.cnf..

测试

我们模拟一个正在写入操作时，主节点down, 看服务器能不能正常切换并不能复制丢失的数据

MariaDB [(none)]> use test;Database changedMariaDB [test]> create table testlog (id int auto_increment primary key,name char(10),age int default 20);Query OK, 0 rows affected (0.01 sec)MariaDB [test]> MariaDB [test]> delimiter $$MariaDB [test]> MariaDB [test]> create proceduresp_testlog() -> begin-> declare i int;-> set i = 1; -> while i <= 100000 -> doinsert into testlog(name,age) values (concat('wang',i),i); -> set i = i +1; -> end while; -> end$$Query OK, 0 rows affected (0.00 sec)MariaDB [test]> MariaDB [test]> delimiter ;MariaDB [test]> call sp_testlog;

正在写入数据时我们及时关闭47服务器，MHA检测到节点，并响应，成功提升其它的为主后退出程序。

[root@MHA ~]#masterha_manager --conf=/etc/mha/app1.cnfMon Aug 12 23:33:22 2019 - [warning] Global configuration file /etc/masterha_default.cnf not found. Skipping.Mon Aug 12 23:33:22 2019 - [info] Reading application default configuration from /etc/mha/app1.cnf..Mon Aug 12 23:33:22 2019 - [info] Reading server configuration from /etc/mha/app1.cnf..Mon Aug 12 23:45:16 2019 - [warning] Global configuration file /etc/masterha_default.cnf not found. Skipping.Mon Aug 12 23:45:16 2019 - [info] Reading application default configuration from /etc/mha/app1.cnf..Mon Aug 12 23:45:16 2019 - [info] Reading server configuration from /etc/mha/app1.cnf..[root@MHA ~]#

我们可以查看日志看一下发生的情况，slave2提升为主

[root@MHA data]#cat mastermha/app1/manager.log ----- Failover Report -----app1: MySQL Master failover 192.168.205.47(192.168.205.47:3306) to 192.168.205.67(192.168.205.67:3306) succeededMaster 192.168.205.47(192.168.205.47:3306) is down!Check MHA Manager logs at MHA:/data/mastermha/app1/manager.log for details.Started automated(non-interactive) failover.The latest slave 192.168.205.57(192.168.205.57:3306) has all relay logs for recovery.Selected 192.168.205.67(192.168.205.67:3306) as a new master.192.168.205.67(192.168.205.67:3306): OK: Applying all logs succeeded.192.168.205.57(192.168.205.57:3306): This host has the latest relay log events.Generating relay diff files from the latest slave succeeded.192.168.205.57(192.168.205.57:3306): OK: Applying all logs succeeded. Slave started, replicating from 192.168.205.67(192.168.205.67:3306)192.168.205.67(192.168.205.67:3306): Resetting slave info succeeded.Master failover to 192.168.205.67(192.168.205.67:3306) completed successfully.

我们来核实一下，在slave2上看一下slave的状态，发现已经没了，因为它是主

MariaDB [(none)]> show slave status\GEmpty set (0.00 sec)

检查一下slave1，发现主节点指向了slave2

MariaDB [test]> show slave status\G*************************** 1. row *************************** Slave_IO_State: Waiting for master to send eventMaster_Host: 192.168.205.67Master_User: repluserMaster_Port: 3306Connect_Retry: 60Master_Log_File: bin.000005Read_Master_Log_Pos: 245 Relay_Log_File: mariadb-relay-bin.000002Relay_Log_Pos: 523Relay_Master_Log_File: bin.000005 Slave_IO_Running: YesSlave_SQL_Running: Yes

在新主节点上看一下是否将read_only off掉，发现是，但不要忘记改回配置文件，如果重启的话又会变成read_only

MariaDB [(none)]> show variables like 'read_only';+---------------+-------+| Variable_name | Value |+---------------+-------+| read_only | OFF |+---------------+-------+1 row in set (0.00 sec)