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MHA（Master High Availability）目前在 MySQL 高可用方面是一个相对成熟的解决方案是一套优秀的作为 MySQL 高可用性环境下故障切换和主从提升的高可用软件。
在 MySQL 故障切换过程中，MHA 能做到在 0~30 秒之内自动完成数据库的故障切换操作，并且在进行故障切换的过程中，MHA 能在最大程度上保证数据的一致性，以达到真正意义上的高可用。
该软件由两部分组成：MHA Manager（管理节点）和 MHA Node（数据节点）。MHA Manager 可以单独部署在一台独立的机器上管理多个 master-slave 集群，也可以部署在一台 slave 节点上。MHA Node 运行在每台 MySQL 服务器上，MHA Manager 会定时探测集群中的 master 节点，当 master 出现故障时，它可以自动将最新数据的 slave 提升为新的 master，然后将所有其他的 slave 重新指向新的 master。整个故障转移过程对应用程序完全透明。
在 MHA 自动故障切换过程中，MHA 试图从宕机的主服务器上保存二进制日志，最大程度的保证数据的不丢失，但这并不总是可行的。例如，如果主服务器硬件故障或无法通过 ssh 访问，MHA 没法保存二进制日志，只进行故障转移而丢失了最新的数据。使用 MySQL 5.5 的半同步复制，可以大大降低数据丢失的风险。MHA 可以与半同步复制结合起来。如果只有一个 slave 已经收到了最新的二进制日志，MHA 可以将最新的二进制日志应用于其他所有的 slave 服务器上，因此可以保证所有节点的数据一致性。
注意：从MySQL5.5开始，MySQL以插件的形式支持半同步复制。
同步概念
如何理解半同步呢？首先我们来看看异步，全同步的概念：
异步复制（Asynchronous replication） MySQL默认的复制即是异步的，主库在执行完客户端提交的事务后会立即将结果返给给客户端，并不关心从库是否已经接收并处理，这样就会有一个问题，主如果crash掉了，此时主上已经提交的事务可能并没有传到从上，如果此时，强行将从提升为主，可能导致新主上的数据不完整。
全同步复制（Fully synchronous replication） 指当主库执行完一个事务，所有的从库都执行了该事务才返回给客户端。因为需要等待所有从库执行完该事务才能返回，所以全同步复制的性能必然会收到严重的影响。
半同步复制（Semisynchronous replication） 介于异步复制和全同步复制之间，主库在执行完客户端提交的事务后不是立刻返回给客户端，而是等待至少一个从库接收到并写到relay log中才返回给客户端。相对于异步复制，半同步复制提高了数据的安全性，同时它也造成了一定程度的延迟，这个延迟最少是一个TCP/IP往返的时间。所以，半同步复制最好在低延时的网络中使用。
总结：异步与半同步异同 默认情况下MySQL的复制是异步的，Master上所有的更新操作写入Binlog之后并不确保所有的更新都被复制到Slave之上。异步操作虽然效率高，但是在Master/Slave出现问题的时候，存在很高数据不同步的风险，甚至可能丢失数据。 MySQL5.5引入半同步复制功能的目的是为了保证在master出问题的时候，至少有一台Slave的数据是完整的。在超时的情况下也可以临时转入异步复制，保障业务的正常使用，直到一台salve追赶上之后，继续切换到半同步模式。
工作原理
相较于其它HA软件，MHA的目的在于维持MySQL Replication中Master库的高可用性，其最大特点是可以修复多个Slave之间的差异日志，最终使所有Slave保持数据一致，然后从中选择一个充当新的Master，并将其它Slave指向它。
从宕机崩溃的master保存二进制日志事件(binlogevents)。
识别含有最新更新的slave。
应用差异的中继日志(relay log)到其它slave。
应用从master保存的二进制日志事件(binlogevents)。
提升一个slave为新master。
使其它的slave连接新的master进行复制。
目前 MHA 主要支持一主多从的架构，要搭建 MHA, 要求一个复制集群中必须最少有三台数据库服务器，一主二从，即一台充当 master，一台充当备用 master，另外一台充当从库，因为至少需要三台服务器，出于机器成本的考虑，淘宝也在该基础上进行了改造，目前淘宝 TMHA 已经支持一主一从。
环境拓扑
其中master1对外提供写服务，备选master（实际为slave，主机名master2）提供读服务，slave也提供相关的读服务，一旦master1宕机，将会把备选master提升为新的master，slave指向新的master，manager作为管理服务器。生产环境中，是有很多从，从的操作都是一样的，这里以两台slave为例，而备选master也作为slave。
环境准备
1、 在配置好IP地址后检查selinux，iptables设置，关闭 selinux ，iptables 服务以便后期主从同步不出错 注：时间要同步 。
2、 在四台机器都配置epel源
[root@manager ~]# wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repo
3、建立ssh无交互登录环境
manager
下面四台主机都需要执行互信，通过for循环把公钥传出去。（互信时直接按回车即可，但是传出去需要允许（yes），然后输入对端密码）
[root@manager ~]# ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):
Created directory '/root/.ssh'.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:8zzNm0tUTQ9bw/E9GQ6+1BbJIPOn5iWPsms6suwmFUU root@manager
The key's randomart image is:
+---[RSA 2048]----+
| .E o o===|
| . = +XO|
| . +oB=|
| . ..= .|
| S .= . |
| . + +o = |
| . +.+o . |
| ..o . +oo |
| ++o.+o=. |
+----[SHA256]-----+
[root@manager ~]# for i in 20 30 40 50;do ssh-copy-id -i ~/.ssh/id_rsa.pub [email protected].$i;done
master1
[root@master1 ~]# ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:cBhASzDVEouISwajm3/j3L3XjLvwYzQzEvkTi2800+k root@master1
The key's randomart image is:
+---[RSA 2048]----+
|o o+*+. |
|+o +.o.o |
|+o. o.o .. |
|o+ oo . |
|+ S+ + . |
| . o % o |
| . o .= % |
| + o . oB E |
| o . o=++ |
+----[SHA256]-----+
[root@master1 ~]# for i in 20 30 40 50;do ssh-copy-id -i ~/.ssh/id_rsa.pub [email protected].$i;done
master2
[root@master2 ~]# ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:MHKw5P1AEBshLUAPUnIKQ/wPtXYAxfMOU/cNErvjZLo root@master2
The key's randomart image is:
+---[RSA 2048]----+
|X*+o@=. .. |
|o*++.% . o.. |
|. .o* % ..o o |
| o B B .. . |
| + = S= |
| . .= . |
| . . |
| . |
| E |
+----[SHA256]-----+
[root@master2 ~]# for i in 20 30 40 50;do ssh-copy-id -i ~/.ssh/id_rsa.pub [email protected].$i;done
slave
[root@slave ~]# ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:3RuS1syMJTLHKzqrHLph3xRDuCh7xDU05i6zqfqnFQM root@slave
The key's randomart image is:
+---[RSA 2048]----+
| + |
| + o . |
| E = . o + . |
| . = + = % |
|. * = o S B B |
| + = o + o . o |
|. * o + . |
| + *.+ o |
|+.=++.o |
+----[SHA256]-----+
[root@slave ~]# for i in 20 30 40 50;do ssh-copy-id -i ~/.ssh/id_rsa.pub [email protected].$i;done
测试ssh交互，远程查看各主机名称
[root@manager ~]# for i in 20 30 40 50 ;do ssh 192.168.8.$i hostname;done
manager
master1
master2
slave
4、配置hosts环境
[root@manager ~]# vim /etc/hosts
#插入四行数据
192.168.8.20 manager
192.168.8.30 master1
192.168.8.40 master2
192.168.8.50 slave
[root@manager ~]# for i in 20 30 40 50;do scp /etc/hosts [email protected].$i:/etc/;done
hosts 100% 240 201.6KB/s 00:00
hosts 100% 240 151.9KB/s 00:00
hosts 100% 240 160.9KB/s 00:00
hosts 100% 240 105.1KB/s 00:00
配置半同步复制
为了尽可能的减少主库硬件损坏宕机造成的数据丢失，因此在配置MHA的同时建议配置成MySQL的半同步复制。 注：mysql半同步插件是由谷歌提供，具体位置/usr/local/mysql/lib/plugin/下，一个是master用的semisync_master.so，一个是slave用的semisync_slave.so。 如果不清楚Plugin的目录，用下面命令查找。
mysql> show variables like '%plugin_dir%';
+---------------+------------------------------+
| Variable_name | Value |
+---------------+------------------------------+
| plugin_dir | /usr/local/mysql/lib/plugin/ |
+---------------+------------------------------+
1 row in set (0.00 sec)
1、分别在主从节点上安装相关的插件（master, Candicate master,slave） 在MySQL上安装插件需要数据库支持动态载入。检查是否支持，用下面命令检测：
mysql> show variables like '%have_dynamic%';
+----------------------+-------+
| Variable_name | Value |
+----------------------+-------+
| have_dynamic_loading | YES |
+----------------------+-------+
1 row in set (0.00 sec)
注意：在所有mysql数据库服务器，安装半同步插件(semisync_master.so,semisync_slave.so)
mysql> install plugin rpl_semi_sync_master soname 'semisync_master.so';
Query OK, 0 rows affected (0.01 sec)
mysql> install plugin rpl_semi_sync_slave soname 'semisync_slave.so';
Query OK, 0 rows affected (0.01 sec)
使用下面命令查看是否成功
mysql> show plugins;
或者
mysql> select * from information_schema.plugins;
查看半同步信息
mysql> show variables like '%rpl_semi_sync%';
+-------------------------------------------+------------+
| Variable_name | Value |
+-------------------------------------------+------------+
| rpl_semi_sync_master_enabled | OFF |
| rpl_semi_sync_master_timeout | 10000 |
| rpl_semi_sync_master_trace_level | 32 |
| rpl_semi_sync_master_wait_for_slave_count | 1 |
| rpl_semi_sync_master_wait_no_slave | ON |
| rpl_semi_sync_master_wait_point | AFTER_SYNC |
| rpl_semi_sync_slave_enabled | OFF |
| rpl_semi_sync_slave_trace_level | 32 |
+-------------------------------------------+------------+
8 rows in set (0.01 sec)
上面可以看到半同复制插件已经安装，只是还没有启用，所以是off 。
2、修改my.cnf文件，配置主从同步
若主MYSQL服务器已经存在，只是后期才搭建从MYSQL服务器，在置配数据同步前应先将主MYSQL服务器的要同步的数据库拷贝到从MYSQL服务器上（如先在主MYSQL上备份数据库，再用备份在从MYSQL服务器上恢复）
master1
[root@master1 ~]# vim /etc/my.cnf
server-id = 1
log-bin=mysql-bin
binlog_format=mixed
log-bin-index=mysql-bin.index
rpl_semi_sync_master_enabled=1
rpl_semi_sync_master_timeout=1000
rpl_semi_sync_slave_enabled=1
relay_log_purge=0
relay-log = relay-bin
relay-log-index = slave-relay-bin.index
[root@master1 ~]# systemctl restart mysqld
注：rpl_semi_sync_master_enabled=1 1表是启用，0表示关闭 rpl_semi_sync_master_timeout=10000：毫秒单位 ，该参数主服务器等待确认消息10秒后，不再等待，变为异步方式。
master2
[root@master2 ~]# vim /etc/my.cnf
server-id = 2
log-bin=mysql-bin
binlog_format=mixed
log-bin-index=mysql-bin.index
relay_log_purge=0
relay-log = relay-bin
relay-log-index = slave-relay-bin.index
rpl_semi_sync_master_enabled=1
rpl_semi_sync_master_timeout=10000
rpl_semi_sync_slave_enabled=1
[root@master2 ~]# systemctl restart mysqld
注：relay_log_purge=0，禁止 SQL 线程在执行完一个 relay log 后自动将其删除，对于MHA场景下，对于某些滞后从库的恢复依赖于其他从库的relay log，因此采取禁用自动删除功能.
slave
[root@slave ~]# vim /etc/my.cnf
server-id = 3
log-bin = mysql-bin
relay-log = relay-bin
relay-log-index = slave-relay-bin.index
read_only = 1
rpl_semi_sync_slave_enabled=1
[root@slave ~]# systemctl restart mysqld
查看状态
查看三台主机的半同步信息
mysql> show variables like '%rpl_semi_sync%';
+-------------------------------------------+------------+
| Variable_name | Value |
+-------------------------------------------+------------+
| rpl_semi_sync_master_enabled | ON |
| rpl_semi_sync_master_timeout | 1000 |
| rpl_semi_sync_master_trace_level | 32 |
| rpl_semi_sync_master_wait_for_slave_count | 1 |
| rpl_semi_sync_master_wait_no_slave | ON |
| rpl_semi_sync_master_wait_point | AFTER_SYNC |
| rpl_semi_sync_slave_enabled | ON |
| rpl_semi_sync_slave_trace_level | 32 |
+-------------------------------------------+------------+
8 rows in set (0.01 sec)
查看三台主机的半同步状态
mysql> show status like '%rpl_semi_sync%';
+--------------------------------------------+-------+
| Variable_name | Value |
+--------------------------------------------+-------+
| Rpl_semi_sync_master_clients | 0 |
| Rpl_semi_sync_master_net_avg_wait_time | 0 |
| Rpl_semi_sync_master_net_wait_time | 0 |
| Rpl_semi_sync_master_net_waits | 0 |
| Rpl_semi_sync_master_no_times | 0 |
| Rpl_semi_sync_master_no_tx | 0 |
| Rpl_semi_sync_master_status | ON |
| Rpl_semi_sync_master_timefunc_failures | 0 |
| Rpl_semi_sync_master_tx_avg_wait_time | 0 |
| Rpl_semi_sync_master_tx_wait_time | 0 |
| Rpl_semi_sync_master_tx_waits | 0 |
| Rpl_semi_sync_master_wait_pos_backtraverse | 0 |
| Rpl_semi_sync_master_wait_sessions | 0 |
| Rpl_semi_sync_master_yes_tx | 0 |
| Rpl_semi_sync_slave_status | OFF |
+--------------------------------------------+-------+
15 rows in set (0.01 sec)
有几个状态参数值得关注：
rpl_semi_sync_master_status ：显示主服务是异步复制模式还是半同步复制模式
rpl_semi_sync_master_clients ：显示有多少个从服务器配置为半同步复制模式
rpl_semi_sync_master_yes_tx ：显示从服务器确认成功提交的数量
rpl_semi_sync_master_no_tx ：显示从服务器确认不成功提交的数量
rpl_semi_sync_master_tx_avg_wait_time ：事务因开启 semi_sync ，平均需要额外等待的时间
rpl_semi_sync_master_net_avg_wait_time ：事务进入等待队列后，到网络平均等待时间
创建用户并指定主从
master1
第一条grant命令是创建一个用于主从复制的帐号，在master1和master2的主机上创建即可。 第二条grant命令是创建MHA管理账号，所有mysql服务器上都需要执行。MHA会在配置文件里要求能远程登录到数据库，所以要进行必要的赋权。
mysql> grant replication slave on *.* to mharep@'192.168.8.%' identified by '123';
Query OK, 0 rows affected, 1 warning (1.00 sec)
mysql> grant all privileges on *.* to manager@'192.168.8.%' identified by '123';
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000005 | 742 | | | |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
master2
mysql> grant replication slave on *.* to mharep@'192.168.8.%' identified by '123';
Query OK, 0 rows affected, 1 warning (10.01 sec)
mysql> grant all privileges on *.* to manager@'192.168.8.%' identified by '123';
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> change master to
-> master_host='192.168.8.30',
-> master_port=3306,
-> master_user='mharep',
-> master_password='123',
-> master_log_file='mysql-bin.000005',
-> master_log_pos=742;
Query OK, 0 rows affected, 2 warnings (0.01 sec)
mysql> start slave;
Query OK, 0 rows affected (0.00 sec)
查看从（master2）的状态（切记不要搞混，master2也是从），以下两个值必须为yes,代表从服务器能正常连接主服务器 Slave_IO_Running:Yes,Slave_SQL_Running:Yes
slave
mysql> grant all privileges on *.* to manager@'192.168.8.%' identified by '123';
Query OK, 0 rows affected, 1 warning (0.04 sec)
mysql> change master to
-> master_host='192.168.8.30',
-> master_port=3306,
-> master_user='mharep',
-> master_password='123',
-> master_log_file='mysql-bin.000005',
-> master_log_pos=742;
Query OK, 0 rows affected, 2 warnings (0.01 sec)
mysql> start slave;
Query OK, 0 rows affected (0.01 sec)
查看从的状态，以下两个值必须为yes,代表从服务器能正常连接主服务器 Slave_IO_Running:Yes Slave_SQL_Running:Yes
查看master1半同步状态
mysql> show status like '%rpl_semi_sync%';
+--------------------------------------------+-------+
| Variable_name | Value |
+--------------------------------------------+-------+
| Rpl_semi_sync_master_clients | 2 |
| Rpl_semi_sync_master_net_avg_wait_time | 0 |
| Rpl_semi_sync_master_net_wait_time | 0 |
| Rpl_semi_sync_master_net_waits | 0 |
| Rpl_semi_sync_master_no_times | 1 |
| Rpl_semi_sync_master_no_tx | 2 |
| Rpl_semi_sync_master_status | ON |
| Rpl_semi_sync_master_timefunc_failures | 0 |
| Rpl_semi_sync_master_tx_avg_wait_time | 0 |
| Rpl_semi_sync_master_tx_wait_time | 0 |
| Rpl_semi_sync_master_tx_waits | 0 |
| Rpl_semi_sync_master_wait_pos_backtraverse | 0 |
| Rpl_semi_sync_master_wait_sessions | 0 |
| Rpl_semi_sync_master_yes_tx | 0 |
| Rpl_semi_sync_slave_status | OFF |
+--------------------------------------------+-------+
15 rows in set (0.01 sec)
配置mysql-mha
manager需要安装node包和manager包，data节点包括原有的MySQL复制结构中的主机，至少3台，即1主2从，当masterfailover后，还能保证主从结构；只需安装node包。manager server：运行监控脚本，负责monitoring 和 auto-failover；
1、 在所有主机上安装mha所依赖的软件包。
[root@manager ~]# yum -y install perl-DBD-MySQL perl-Config-Tiny perl-Log-Dispatch perl-Parallel-ForkManager perl-Config-IniFiles ncftp perl-Params-Validate perl-CPAN perl-Test-Mock-LWP.noarch perl-LWP-Authen-Negotiate.noarch perl-devel perl-ExtUtils-CBuilder perl-ExtUtils-MakeMaker
2、在管理节点（manager）需要两个都安装：mha4mysql-node-0.56.tar.gz和mha4mysql-manager-0.56.tar.gz ，在另外三台数据库节点只要安装MHA的node节点。
软件下载 yoshinorim (Yoshinori Matsunobu) · GitHub
管理节点安装mha4mysql-manager-0.58.tar.gz
[root@manager ~]# tar zxf mha4mysql-manager-0.58.tar.gz
[root@manager ~]# cd mha4mysql-manager-0.58/
[root@manager mha4mysql-manager-0.58]# perl Makefile.PL
[root@manager mha4mysql-manager-0.58]# make && make install
[root@manager mha4mysql-manager-0.58]# mkdir /etc/masterha
[root@manager mha4mysql-manager-0.58]# mkdir -p /masterha/app1
[root@manager mha4mysql-manager-0.58]# mkdir /scripts
[root@manager mha4mysql-manager-0.58]# cp samples/conf/* /etc/masterha/
[root@manager mha4mysql-manager-0.58]# cp samples/scripts/* /scripts
注意：在所有数据库（包括管理节点的四台服务器）上安装mha4mysql-node-0.56.tar.gz
[root@manager ~]# tar zxf mha4mysql-node-0.58.tar.gz
[root@manager ~]# cd mha4mysql-node-0.58/
[root@manager mha4mysql-node-0.58]# perl Makefile.PL
[root@manager mha4mysql-node-0.58]# make && make install
配置mha
与绝大多数Linux应用程序类似，MHA的正确使用依赖于合理的配置文件。MHA的配置文件与mysql的my.cnf文件配置相似，采取的是param=value的方式来配置，配置文件位于管理节点，通常包括每一个mysql server的主机名，mysql用户名，密码，工作目录等等。 编辑/etc/masterha/app1.conf，内容如下：
[root@manager ~]# vim /etc/masterha/app1.cnf
[server default]
manager_workdir=/masterha/app1
manager_log=/masterha/app1/manager.log
user=manager
password=123
ssh_user=root
repl_user=mharep
repl_password=123
ping_interval=1
[server1]
hostname=192.168.8.30
port=3306
master_binlog_dir=/usr/local/mysql/data
candidate_master=1
[server2]
hostname=192.168.8.40
port=3306
master_binlog_dir=/usr/local/mysql/data
candidate_master=1
[server3]
hostname=192.168.8.50
port=3306
master_binlog_dir=/usr/local/mysql/data
no_master=1
配关配置项的解释如下：
manager_workdir=/masterha/app1 #设置manager的工作目录
manager_log=/masterha/app1/manager.log #设置manager的日志
user=manager #设置监控用户manager
password=123 #监控用户manager的密码
ssh_user=root #ssh连接用户
repl_user=mharep #主从复制用户
repl_password=123 #主从复制用户密码
ping_interval=1 #设置监控主库，发送ping包的时间间隔，默认是3秒，尝试三次没有回应的时候自动进行
railover master_binlog_dir=/usr/local/mysql/data #设置master 保存binlog的位置，以便MHA可以找到master的日志，我这里的也就是mysql的数据目录
candidate_master=1 #设置为候选master，如果设置该参数以后，发生主从切换以后将会将此从库提升为主库
验证
SSH 有效性验证
[root@manager ~]# masterha_check_ssh --global_conf=/etc/masterha/masterha_default.cnf --conf=/etc/masterha/app1.cnf
Tue Apr 4 13:44:58 2023 - [info] Reading default configuration from /etc/masterha/masterha_default.cnf..
Tue Apr 4 13:44:58 2023 - [info] Reading application default configuration from /etc/masterha/app1.cnf..
Tue Apr 4 13:44:58 2023 - [info] Reading server configuration from /etc/masterha/app1.cnf..
Tue Apr 4 13:44:58 2023 - [info] Starting SSH connection tests..
Tue Apr 4 13:45:01 2023 - [debug]
Tue Apr 4 13:44:59 2023 - [debug] Connecting via SSH from [email protected](192.168.8.50:22) to [email protected](192.168.8.30:22)..
Tue Apr 4 13:45:00 2023 - [debug] ok.
Tue Apr 4 13:45:00 2023 - [debug] Connecting via SSH from [email protected](192.168.8.50:22) to [email protected](192.168.8.40:22)..
Tue Apr 4 13:45:00 2023 - [debug] ok.
Tue Apr 4 13:45:01 2023 - [debug]
Tue Apr 4 13:44:59 2023 - [debug] Connecting via SSH from [email protected](192.168.8.40:22) to [email protected](192.168.8.30:22)..
Tue Apr 4 13:44:59 2023 - [debug] ok.
Tue Apr 4 13:44:59 2023 - [debug] Connecting via SSH from [email protected](192.168.8.40:22) to [email protected](192.168.8.50:22)..
Tue Apr 4 13:45:00 2023 - [debug] ok.
Tue Apr 4 13:45:01 2023 - [debug]
Tue Apr 4 13:44:58 2023 - [debug] Connecting via SSH from [email protected](192.168.8.30:22) to [email protected](192.168.8.40:22)..
Tue Apr 4 13:44:59 2023 - [debug] ok.
Tue Apr 4 13:44:59 2023 - [debug] Connecting via SSH from [email protected](192.168.8.30:22) to [email protected](192.168.8.50:22)..
Tue Apr 4 13:45:00 2023 - [debug] ok.
Tue Apr 4 13:45:01 2023 - [info] All SSH connection tests passed successfully.
集群复制的有效性验证
所有mysql必须都启动，验证成功的话会自动识别出所有服务器和主从状况 注：验证成功的话会自动识别出所有服务器和主从状况 在验证时，若遇到这个错误：Can't exec "mysqlbinlog" ...... 解决方法是在所有服务器上执行：
ln -s /usr/local/mysql/bin/* /usr/local/bin/
[root@manager ~]# masterha_check_repl --global_conf=/etc/masterha/masterha_default.cnf --conf=/etc/masterha/app1.cnf
Tue Apr 4 13:48:03 2023 - [info] Reading default configuration from /etc/masterha/masterha_default.cnf..
Tue Apr 4 13:48:03 2023 - [info] Reading application default configuration from /etc/masterha/app1.cnf..
Tue Apr 4 13:48:03 2023 - [info] Reading server configuration from /etc/masterha/app1.cnf..
Tue Apr 4 13:48:03 2023 - [info] MHA::MasterMonitor version 0.58.
Tue Apr 4 13:48:04 2023 - [info] GTID failover mode = 0
Tue Apr 4 13:48:04 2023 - [info] Dead Servers:
Tue Apr 4 13:48:04 2023 - [info] Alive Servers:
Tue Apr 4 13:48:04 2023 - [info] 192.168.8.30(192.168.8.30:3306)
Tue Apr 4 13:48:04 2023 - [info] 192.168.8.40(192.168.8.40:3306)
Tue Apr 4 13:48:04 2023 - [info] 192.168.8.50(192.168.8.50:3306)
Tue Apr 4 13:48:04 2023 - [info] Alive Slaves:
Tue Apr 4 13:48:04 2023 - [info] 192.168.8.40(192.168.8.40:3306) Version=5.7.40-log (oldest major version between slaves) log-bin:enabled
Tue Apr 4 13:48:04 2023 - [info] Replicating from 192.168.8.30(192.168.8.30:3306)
Tue Apr 4 13:48:04 2023 - [info] Primary candidate for the new Master (candidate_master is set)
Tue Apr 4 13:48:04 2023 - [info] 192.168.8.50(192.168.8.50:3306) Version=5.7.40-log (oldest major version between slaves) log-bin:enabled
Tue Apr 4 13:48:04 2023 - [info] Replicating from 192.168.8.30(192.168.8.30:3306)
Tue Apr 4 13:48:04 2023 - [info] Not candidate for the new Master (no_master is set)
Tue Apr 4 13:48:04 2023 - [info] Current Alive Master: 192.168.8.30(192.168.8.30:3306)
Tue Apr 4 13:48:04 2023 - [info] Checking slave configurations..
Tue Apr 4 13:48:04 2023 - [info] read_only=1 is not set on slave 192.168.8.40(192.168.8.40:3306).
Tue Apr 4 13:48:04 2023 - [warning] relay_log_purge=0 is not set on slave 192.168.8.50(192.168.8.50:3306).
Tue Apr 4 13:48:04 2023 - [info] Checking replication filtering settings..
Tue Apr 4 13:48:04 2023 - [info] binlog_do_db= , binlog_ignore_db=
Tue Apr 4 13:48:04 2023 - [info] Replication filtering check ok.
Tue Apr 4 13:48:04 2023 - [info] GTID (with auto-pos) is not supported
Tue Apr 4 13:48:04 2023 - [info] Starting SSH connection tests..
Tue Apr 4 13:48:07 2023 - [info] All SSH connection tests passed successfully.
Tue Apr 4 13:48:07 2023 - [info] Checking MHA Node version..
Tue Apr 4 13:48:07 2023 - [info] Version check ok.
Tue Apr 4 13:48:07 2023 - [info] Checking SSH publickey authentication settings on the current master..
Tue Apr 4 13:48:08 2023 - [info] HealthCheck: SSH to 192.168.8.30 is reachable.
Tue Apr 4 13:48:08 2023 - [info] Master MHA Node version is 0.58.
Tue Apr 4 13:48:08 2023 - [info] Checking recovery script configurations on 192.168.8.30(192.168.8.30:3306)..
Tue Apr 4 13:48:08 2023 - [info] Executing command: save_binary_logs --command=test --start_pos=4 --binlog_dir=/usr/local/mysql/data --output_file=/data/log/masterha/save_binary_logs_test --manager_version=0.58 --start_file=mysql-bin.000005
Tue Apr 4 13:48:08 2023 - [info] Connecting to [email protected](192.168.8.30:22)..
Creating /data/log/masterha if not exists.. ok.
Checking output directory is accessible or not..
ok.
Binlog found at /usr/local/mysql/data, up to mysql-bin.000005
Tue Apr 4 13:48:08 2023 - [info] Binlog setting check done.
Tue Apr 4 13:48:08 2023 - [info] Checking SSH publickey authentication and checking recovery script configurations on all alive slave servers..
Tue Apr 4 13:48:08 2023 - [info] Executing command : apply_diff_relay_logs --command=test --slave_user='manager' --slave_host=192.168.8.40 --slave_ip=192.168.8.40 --slave_port=3306 --workdir=/data/log/masterha --target_version=5.7.40-log --manager_version=0.58 --relay_log_info=/usr/local/mysql/data/relay-log.info --relay_dir=/usr/local/mysql/data/ --slave_pass=xxx
Tue Apr 4 13:48:08 2023 - [info] Connecting to [email protected](192.168.8.40:22)..
Creating directory /data/log/masterha.. done.
Checking slave recovery environment settings..
Opening /usr/local/mysql/data/relay-log.info ... ok.
Relay log found at /usr/local/mysql/data, up to relay-bin.000002
Temporary relay log file is /usr/local/mysql/data/relay-bin.000002
Checking if super_read_only is defined and turned on.. not present or turned off, ignoring.
Testing mysql connection and privileges..
mysql: [Warning] Using a password on the command line interface can be insecure.
done.
Testing mysqlbinlog output.. done.
Cleaning up test file(s).. done.
Tue Apr 4 13:48:09 2023 - [info] Executing command : apply_diff_relay_logs --command=test --slave_user='manager' --slave_host=192.168.8.50 --slave_ip=192.168.8.50 --slave_port=3306 --workdir=/data/log/masterha --target_version=5.7.40-log --manager_version=0.58 --relay_log_info=/usr/local/mysql/data/relay-log.info --relay_dir=/usr/local/mysql/data/ --slave_pass=xxx
Tue Apr 4 13:48:09 2023 - [info] Connecting to [email protected](192.168.8.50:22)..
Creating directory /data/log/masterha.. done.
Checking slave recovery environment settings..
Opening /usr/local/mysql/data/relay-log.info ... ok.
Relay log found at /usr/local/mysql/data, up to relay-bin.000002
Temporary relay log file is /usr/local/mysql/data/relay-bin.000002
Checking if super_read_only is defined and turned on.. not present or turned off, ignoring.
Testing mysql connection and privileges..
mysql: [Warning] Using a password on the command line interface can be insecure.
done.
Testing mysqlbinlog output.. done.
Cleaning up test file(s).. done.
Tue Apr 4 13:48:09 2023 - [info] Slaves settings check done.
Tue Apr 4 13:48:09 2023 - [info]
192.168.8.30(192.168.8.30:3306) (current master)
+--192.168.8.40(192.168.8.40:3306)
+--192.168.8.50(192.168.8.50:3306)
Tue Apr 4 13:48:09 2023 - [info] Checking replication health on 192.168.8.40..
Tue Apr 4 13:48:09 2023 - [info] ok.
Tue Apr 4 13:48:09 2023 - [info] Checking replication health on 192.168.8.50..
Tue Apr 4 13:48:09 2023 - [info] ok.
Tue Apr 4 13:48:09 2023 - [warning] master_ip_failover_script is not defined.
Tue Apr 4 13:48:09 2023 - [warning] shutdown_script is not defined.
Tue Apr 4 13:48:09 2023 - [info] Got exit code 0 (Not master dead).
MySQL Replication Health is OK.
启动manager
注：在应用Unix/Linux时，我们一般想让某个程序在后台运行，于是我们将常会用 & 在程序结尾来让程序自动运行。比如我们要运行mysql在后台： /usr/local/mysql/bin/mysqld_safe –user=mysql &。可是有很多程序并不想mysqld一样，这样我们就需要nohup命令。
[root@manager mha4mysql-manager-0.58]# cd /masterha/
[root@manager masterha]# nohup masterha_manager --conf/etc/masterha/app1.cnf &> /tmp/mha_manager.log &
[2] 99442
检查状态
[root@manager masterha]# masterha_check_status --conf=/etc/masterha/app1.cnf
app1 (pid:99277) is running(0:PING_OK), master:192.168.8.30
故障转移验证
(自动failover) master dead后，MHA当时已经开启，master2（Slave）会自动failover为Master. 验证的方式是先停掉 master1，因为之前的配置文件中，把master2作为了候选人，那么就到 slave 上查看 master 的 IP 是否变为了master2 的 IP
1、停掉 master 在master1上把 mysql 停掉
[root@master1 ~]# systemctl stop mysqld
2、查看 MHA 日志 上面的配置文件中指定了日志位置为/masterha/app1/manager.log
[root@manager ~]# cat /masterha/app1/manager.log
----- Failover Report -----
app1: MySQL Master failover 192.168.8.30(192.168.8.30:3306) to 192.168.8.40(192.168.8.40:3306) succeeded
Master 192.168.8.30(192.168.8.30:3306) is down!
Check MHA Manager logs at manager:/masterha/app1/manager.log for details.
Started automated(non-interactive) failover.
The latest slave 192.168.8.40(192.168.8.40:3306) has all relay logs for recovery.
Selected 192.168.8.40(192.168.8.40:3306) as a new master.
192.168.8.40(192.168.8.40:3306): OK: Applying all logs succeeded.
192.168.8.50(192.168.8.50:3306): This host has the latest relay log events.
Generating relay diff files from the latest slave succeeded.
192.168.8.50(192.168.8.50:3306): OK: Applying all logs succeeded. Slave started, replicating from 192.168.8.40(192.168.8.40:3306)
192.168.8.40(192.168.8.40:3306): Resetting slave info succeeded.
Master failover to 192.168.8.40(192.168.8.40:3306) completed successfully.
从日志信息中可以看到 master failover 已经成功了，并可以看出故障转移的大体流程
3、检查 slave2 的复制 登录 slave（192.168.8.50） 的Mysql，查看 slave 状态
可以看到 master 的 IP 现在为 192.168.8.40, 已经切换到和192.168.8.40同步了，本来是和192.168.8.30同步的，说明 MHA 已经把master2提升为了新的 master，IO线程和SQL线程也正确运行，MHA搭建成功。
MHA Manager 端日常操作
1、检查是否有下列文件，有则删除。 发生主从切换后，MHAmanager服务会自动停掉，且在manager_workdir（/masterha/app1）目录下面生成文件app1.failover.complete，若要启动MHA，必须先确保无此文件。
主从转移后，需要删除下面两个文件。
ll /masterha/app1/app1.failover.complete
ll /masterha/app1/app1.failover.error
2、检查MHA复制检查：（需要把master设置成candicatade的从服务器）
mysql> change master to
-> master_host='192.168.8.40',
-> master_port=3306,
-> master_user='mharep',
-> master_password='123',
-> master_log_file='mysql-bin.000007',
-> master_log_pos=154;
Query OK, 0 rows affected, 2 warnings (0.03 sec)
mysql> start slave;
Query OK, 0 rows affected (0.01 sec)
3、登录manager
[root@manager ~]# masterha_check_repl --conf=/etc/masterha/app1.cnf
#省略部分内容
Thu Apr 6 19:58:27 2023 - [info] Checking replication health on 192.168.8.30..
Thu Apr 6 19:58:27 2023 - [info] ok.
Thu Apr 6 19:58:27 2023 - [info] Checking replication health on 192.168.8.50..
Thu Apr 6 19:58:27 2023 - [info] ok.
Thu Apr 6 19:58:27 2023 - [warning] master_ip_failover_script is not defined.
Thu Apr 6 19:58:27 2023 - [warning] shutdown_script is not defined.
Thu Apr 6 19:58:27 2023 - [info] Got exit code 0 (Not master dead).
MySQL Replication Health is OK.
4、停止MHA：
[root@manager ~]# masterha_stop --conf=/etc/masterha/app1.cnf
Stopped app1 successfully.
5、启动MHA：
[root@manager ~]# nohup masterha_manager --conf=/etc/masterha/app1.cnf &>/tmp/mha_manager.log &
[1] 101196
当有slave 节点宕掉时，默认是启动不了的，加上 --ignore_fail_on_start 即使有节点宕掉也能启动MHA，如下：
nohup masterha_manager --conf=/etc/masterha/app1.cnf --ignore_fail_on_start &>/tmp/mha_manager.log &
6、检查状态：
[root@manager ~]# masterha_check_status --conf=/etc/masterha/app1.cnf
app1 (pid:101303) is running(0:PING_OK), master:192.168.8.40
7、检查日志：
[root@manager ~]# tail -f /masterha/app1/manager.log
8、主从切换后续工作
重构： 重构就是你的主挂了，切换到Candicate master上，Candicate master变成了主，因此重构的一种方案原主库修复成一个新的slave 主库切换后，把原主库修复成新从库，然后重新执行以上5步。
登录master1主机
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.8.40
Master_User: mharep
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000007
Read_Master_Log_Pos: 154
Relay_Log_File: relay-bin.000002
Relay_Log_Pos: 320
Relay_Master_Log_File: mysql-bin.000007
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
启动manager
[root@manager ~]# nohup masterha_manager --conf=/etc/masterha/app1.cnf &> /tmp/mha_manager.log &
[root@manager ~]# masterha_check_status --conf=/etc/masterha/app1.cnf
app1 (pid:101303) is running(0:PING_OK), master:192.168.8.40
注意：如果正常，会显示"PING_OK"，否则会显示"NOT_RUNNING"，这代表MHA监控没有开启。定期删除中继日志 在配置主从复制中，slave上设置了参数relay_log_purge=0，所以slave节点需要定期删除中继日志，建议每个slave节点删除中继日志的时间错开。
[root@manager ~]# crontab -e
0 5 * * * /usr/local/bin/purge_relay_logs - -user=root --password=123 --port=3306 --disable_relay_log_purge >> /var/log/purge_relay.log 2>&1
本文转载自: https://blog.csdn.net/qq_61116007/article/details/130057994
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版权归原作者 大虾好吃吗 所有， 如有侵权，请联系我们删除。