MHA功能：
- 从故障的mysql保存二进制日志时间(binlog events);
- 识别含有最新更新的slave；
- 应用差异的中继日志（relay log）到其他的slave；
- 应用从master保存的二进制日志文事件；
- 提升一个slave为新的master；
- 是其他的slave连接新的master进行复制；
MHA环境搭建：
- manager节点：192.168.125.210
- node1节点:192.168.125.200
- node2节点：192.168.125.201
- node3节点:192.168.125.202
1，首先要配置mysql主从复制。
2，SSH免密钥互相访问配置：
1[root@localhost ~]# ssh-keygen -t rsa -P '' //生成公钥 2Generating public/private rsa key pair. 3Enter file in which to save the key (/root/.ssh/id_rsa): 4Created directory '/root/.ssh'. 5Your identification has been saved in /root/.ssh/id_rsa. 6Your public key has been saved in /root/.ssh/id_rsa.pub. 7The key fingerprint is: 8SHA256:LzSIfKtqa4fh70k5xAreOULBySucDWzUsHf4+6PlHmQ root@localhost.localdomain 9The key's randomart image is: 10+---[RSA 2048]----+ 11| oo | 12|= o.. | 13| X o . | 14|o Boo. . | 15|o= .=.oES | 16|+.oo.o+o o | 17| +.*+..o. . | 18| *.o++... | 19| oo*=.o+. | 20+----[SHA256]-----+ 21[root@localhost ~]# cat .ssh/id_rsa.pub > .ssh/authorized_keys //导入到本地认证文件 22[root@localhost ~]# chmod go= .ssh/authorized_keys 23[root@localhost ~]# scp .ssh/id_rsa .ssh/authorized_keys 192.168.125.200:/root/.ssh/ //SCP到各个节点就可以互相访问了。 24[root@localhost ~]# scp -p .ssh/id_rsa .ssh/authorized_keys 192.168.125.201:/root/.ssh/ 25[root@localhost ~]# scp -p .ssh/id_rsa .ssh/authorized_keys 192.168.125.202:/root/.ssh/
3，安装MHA；
下载地址： https://downloads.mariadb.com/MHA/mha4mysql-manager-0.55-0.el6.noarch.rpm https://downloads.mariadb.com/MHA/mha4mysql-node-0.54-0.el6.noarch.rpm 需要安装epel源，通过yum安装，在manager安装（manager和node包），在其他主从复制节点安装‘node’包。
4，配置MHA：
1root@manager ~]# cat /etc/masterha/app1.cnf 2[server default] 3manager_workdir=/etc/masterha/app1 #配置manager的工作目录 4manager_log=/etc/masterha/app1/manager.log #设置manager的日志 5master_binlog_dir=/var/lib/mysql/ #设置master保存binlog的位置，以便MHA可以找到master的日志 6user=mhaadmin #设置监控用的root权限账号，每个节点需要创建。 7password=123123 #密码 8ssh_user=root #设置ssh的登陆用户名。 9repl_user=glq #设置复制环境中的复制用户名。 10repl_password=123123 #密码 11 12[server1] 13hostname=192.168.125.200 14port=3306 15#master_binlog_dir=/var/lib64/mysql 16candidate_master=1 #设置为候选master，即使这个库不是集群中最新的slave，也会选择为master。 17#check_repl_delay=0 #默认情况下如果一个slave落后master 100M的relay logs的话，MHA将不会选择该slave作为一个新的master，因为对于这个slave的恢复需要花费很长时间，通过设置check_repl_delay=0,MHA触发切换在选择一个新的master的时候将会忽略复制延时，这个参数对于设置了candidate_master=1的主机非常有用，因为这个候选主在切换的过程中一定是新的master 18 19[server2] 20hostname=192.168.125.201 21port=3306 22#master_binlog_dir=/var/lib64/mysql 23candidate_master=1 24 25[server3] 26hostname=192.168.125.202 27port=3306 28#master_binlog_dir=/var/lib64/mysql 29#ignore_fail=1 30#no_master=1
5，测试MHA；
1[root@manager ~]# masterha_check_ssh --conf=/etc/masterha/app1.cnf #测试ssh连接是否正常。 2Wed Mar 14 15:44:16 2018 - [info] All SSH connection tests passed successfully. 3[root@manager ~]# masterha_check_repl --conf=/etc/masterha/app1.cnf #测试主从配置是否正常 4Wed Mar 14 15:45:09 2018 - [info] 5192.168.125.200 (current master) 6 +--192.168.125.201 7 +--192.168.125.202 8Wed Mar 14 15:45:09 2018 - [info] Checking replication health on 192.168.125.201.. 9Wed Mar 14 15:45:09 2018 - [info] ok. 10Wed Mar 14 15:45:09 2018 - [info] Checking replication health on 192.168.125.202.. 11Wed Mar 14 15:45:09 2018 - [info] ok. 12Wed Mar 14 15:45:09 2018 - [warning] master_ip_failover_script is not defined. 13Wed Mar 14 15:45:09 2018 - [warning] shutdown_script is not defined. 14Wed Mar 14 15:45:09 2018 - [info] Got exit code 0 (Not master dead). 15MySQL Replication Health is OK.
6，启动MHA；
1[root@manager ~]# masterha_manager --conf=/etc/masterha/app1.cnf 2Wed Mar 14 15:46:24 2018 - [warning] Global configuration file /etc/masterha_default.cnf not found. Skipping. 3Wed Mar 14 15:46:24 2018 - [info] Reading application default configurations from /etc/masterha/app1.cnf.. 4Wed Mar 14 15:46:24 2018 - [info] Reading server configurations from /etc/masterha/app1.cnf..
####停止master的mysql之后的状态：
1[root@manager ~]# masterha_manager --conf=/etc/masterha/app1.cnf 2Wed Mar 14 15:46:24 2018 - [warning] Global configuration file /etc/masterha_default.cnf not found. Skipping. 3Wed Mar 14 15:46:24 2018 - [info] Reading application default configurations from /etc/masterha/app1.cnf.. 4Wed Mar 14 15:46:24 2018 - [info] Reading server configurations from /etc/masterha/app1.cnf.. 5 Creating /var/tmp if not exists.. ok. #检测到master不存在 6 Checking output directory is accessible or not.. 7 ok. 8 Binlog found at /var/lib/mysql/, up to master-bin.000003 #发现二进制日志。 9Wed Mar 14 15:47:08 2018 - [warning] Global configuration file /etc/masterha_default.cnf not found. Skipping. 10Wed Mar 14 15:47:08 2018 - [info] Reading application default configurations from /etc/masterha/app1.cnf.. 11Wed Mar 14 15:47:08 2018 - [info] Reading server configurations from /etc/masterha/app1.cnf..
后台运行MHA指令：
1[root@manager ~]# nohup master_manager --conf=/etc/masterha/app1.cnf >/etc/masterha/app1/manager.log 2>&1 & 2[1] 2832
手动切换从节点为主节点：
1[root@manager ~]# masterha_master_switch --master_state=alive --conf=/etc/masterha/app1.cnf --orig_master_is_new_slave --running_updates_limit=3600 --interactive=0 2Wed Mar 14 15:52:45 2018 - [info] 3Wed Mar 14 15:52:45 2018 - [info] * Phase 5: New master cleanup phase.. 4Wed Mar 14 15:52:45 2018 - [info] 5Wed Mar 14 15:52:45 2018 - [info] 192.168.125.201: Resetting slave info succeeded. 6Wed Mar 14 15:52:45 2018 - [info] Switching master to 192.168.125.201(192.168.125.201:3306) completed successfully.
停止MHA manager监控：
[root@manager ~]# masterha_stop --conf=/etc/masterha/app1.cnf