1. Overview of MHA
1. Concept of MHA
MHA (MasterHigh Availability) is an excellent set of failover and master-slave replication software in a MySQL high-availability environment.
The emergence of MHA is to solve the single point problem of MySQL.
During the MySQL failover process, MHA can automatically complete the failover operation within 0-30 seconds.
MHA can ensure data consistency to the greatest extent during the failover process to achieve true high availability.
2. Composition of MHA
●MHA Node (data node)
MHA Node runs on every MySQL server.
●MHA Manager (management node)
MHA Manager can be deployed on an independent machine to manage multiple master-slave clusters; it can also be deployed on a slave node.
MHA Manager will periodically detect the master node in the cluster. When the master fails, it can automatically promote the slave with the latest data to the new master, and then redirect all other slaves to the new master. The entire failover process is completely transparent to the application.
3．Features of MHA
●During the automatic failover process, MHA attempts to save the binary log from the downed main server to ensure that data is not lost to the greatest extent
●Using semi-synchronous replication, the risk of data loss can be greatly reduced. If only one slave has received the latest binary log, MHA can apply the latest binary log to all other slave servers, thus ensuring that the data of all nodes is consistent. sex
●Currently MHA supports one master and multiple slaves architecture, with at least three services, that is, one master and two slaves
2. Steps to build MySQL MHA
1. Experimental ideas:
1.1. MHA architecture
1) Database installation
2) One master and two slaves
3)MHA construction
1.2. Fault simulation
1) The main database is invalid
2) The alternative main library becomes the main library
3) The original failed master database is restored and rejoins the MHA to become a slave database.
2. Environment preparation
MHA manager node server: CentOS7.4 (64-bit) manager/192.168.229.50, install MHA node and manager components
Master 节点服务器：CentOS7.4(64 位) mysql1/192.168.229.90，安装mysql5.7、MHA node 组件
Slave1 节点服务器：CentOS7.4(64 位) mysql2/192.168.229.80，安装mysql5.7、MHA node 组件
Slave2 节点服务器：CentOS7.4(64 位) mysql3/192.168.229.70，安装mysql5.7、MHA node 组件
systemctl stop firewalld
systemctldisable firewalld
setenforce 0
3、修改 Master、Slave1、Slave2 节点的主机名
Master、Slave1、Slave2 节点上安装 mysql5.7
hostnamectl set-hostname Mysql1
hostnamectl set-hostname Mysql2
hostnamectl set-hostname Mysql34、修改 Master、Slave1、Slave2 节点的 Mysql主配置文件/etc/my.cnf
##Master 节点##
vim /etc/my.cnf
[mysqld]
server-id = 1
log_bin = master-bin
log-slave-updates =true
systemctl restart mysqld
##Slave1、Slave2 节点##
vim /etc/my.cnf
server-id =2 #三台服务器的 server-id 不能一样
log_bin = master-bin
relay-log = relay-log-bin
relay-log-index = slave-relay-bin.index systemctl restart mysqld 5、在 Master、Slave1、Slave2 节点上都创建两个软链接
ln -s /usr/local/mysql/bin/mysql /usr/sbin/
ln -s /usr/local/mysql/bin/mysqlbinlog /usr/sbin/
6、配置 mysql 一主两从
(1)所有数据库节点进行 mysql 授权
mysql -uroot -p
grant replication slaveon *.* to 'myslave'@'192.168.229.%' identified by '12345'; #从数据库同步使用 grant all privileges on *.* to 'mha'@'192.168.229.%' identified by 'manager'; #manager 使用 grant all privileges on *.* to 'mha'@'Mysql1' identified by 'manager'; #防止从库通过主机名连接不上主库 grant all privileges on *.* to 'mha'@'Mysql2' identified by 'manager'; grant all privileges on *.* to 'mha'@'Mysql3' identified by 'manager'; flush privileges; (2)在 Master 节点查看二进制文件和同步点
show masterstatus;
(3)在 Slave1、Slave2 节点执行同步操作
change masterto master_host='192.168.229.90',master_user='myslave',master_password='12345',master_log_file='master-bin.000001',master_log_pos=1215; start slave; (4)在 Slave1、Slave2 节点查看数据同步结果
show slave status\G
//确保 IO 和 SQL 线程都是 Yes，代表同步正常。 Slave_IO_Running: Yes Slave_SQL_Running: Yes (5)两个从库必须设置为只读模式：
set global read_only=1;
(6)插入数据测试数据库同步
##在 Master 主库插入条数据，测试是否同步##
create database test_db;
use test_db;
create table test(id int);
insert into test(id) values (1); 7、安装 MHA 软件
(1)所有服务器上都安装 MHA 依赖的环境，首先安装 epel 源
yuminstall epel-release --nogpgcheck -y
yum install -y perl-DBD-MySQL \
perl-Config-Tiny \
perl-Log-Dispatch \
perl-Parallel-ForkManager \
perl-ExtUtils-CBuilder \ perl-ExtUtils-MakeMaker \ perl-CPAN (2)安装 MHA 软件包，先在所有服务器上必须先安装 node 组件
对于每个操作系统版本不一样，这里 CentOS7.4 必须选择 0.57 版本。
在所有服务器上必须先安装 node 组件，最后在 MHA-manager 节点上安装 manager 组件，因为 manager 依赖 node 组件。
cd /opt
tar zxvf mha4mysql-node-0.57.tar.gz
cd mha4mysql-node-0.57
perl Makefile.PL
make && make install
(3)在 MHA manager 节点上安装 manager 组件
cd /opt
tar zxvf mha4mysql-manager-0.57.tar.gz
cd mha4mysql-manager-0.57
perl Makefile.PL
make && make install
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#manager 组件安装后在/usr/local/bin 下面会生成几个工具，主要包括以下几个：
masterha_check_ssh 检查 MHA 的 SSH 配置状况
masterha_check_repl 检查 MySQL 复制状况
masterha_manger 启动 manager的脚本
masterha_check_status 检测当前 MHA 运行状态
masterha_master_monitor 检测 master 是否宕机
masterha_master_switch 控制故障转移(自动或者手动)
masterha_conf_host 添加或删除配置的 server 信息
masterha_stop 关闭manager
#node 组件安装后也会在/usr/local/bin 下面会生成几个脚本(这些工具通常由 MHAManager 的脚本触发，无需人为操作)主要如下：
save_binary_logs 保存和复制 master 的二进制日志
apply_diff_relay_logs 识别差异的中继日志事件并将其差异的事件应用于其他的 slave
filter_mysqlbinlog 去除不必要的 ROLLBACK 事件(MHA 已不再使用这个工具)
purge_relay_logs 清除中继日志(不会阻塞 SQL 线程)
8．在所有服务器上配置无密码认证
(1)在 manager 节点上配置到所有数据库节点的无密码认证
ssh-keygen -t rsa#一路按回车键
ssh-copy-id 192.168.229.80
ssh-copy-id 192.168.229.70 ssh-copy-id 192.168.229.90 (2)在 mysql1 上配置到数据库节点 mysql2 和 mysql3 的无密码认证
ssh-keygen -t rsa
ssh-copy-id 192.168.229.80 ssh-copy-id 192.168.229.70 (3)在 mysql2 上配置到数据库节点 mysql1 和 mysql3 的无密码认证
ssh-keygen -t rsa
ssh-copy-id 192.168.229.90 ssh-copy-id 192.168.229.80 (4)在 mysql3 上配置到数据库节点 mysql1 和 mysql2 的无密码认证
ssh-keygen -t rsa
ssh-copy-id 192.168.229.90 ssh-copy-id 192.168.229.80 9．在 manager 节点上配置 MHA
(1)在 manager 节点上复制相关脚本到/usr/local/bin 目录
cp -rp /opt/mha4mysql-manager-0.57/samples/scripts /usr/local/bin
//拷贝后会有四个执行文件
ll /usr/local/bin/scripts/
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master_ip_failover #自动切换时 VIP 管理的脚本
master_ip_online_change #在线切换时 vip 的管理
power_manager #故障发生后关闭主机的脚本
send_report #因故障切换后发送报警的脚本
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(2)复制上述的自动切换时 VIP 管理的脚本到 /usr/local/bin 目录，这里使用master_ip_failover脚本来管理 VIP 和故障切换
cp /usr/local/bin/scripts/master_ip_failover /usr/local/bin
(3)修改内容如下：(删除原有内容，直接复制并修改vip相关参数)
vim /usr/local/bin/master_ip_failover
#!/usr/bin/env perl
use strict;
use warnings FATAL => 'all'; use Getopt::Long; my ( $command, $ssh_user, $orig_master_host, $orig_master_ip, $orig_master_port, $new_master_host, $new_master_ip, $new_master_port ); #############################添加内容部分######################################### my $vip = '192.168.229.200'; #指定vip的地址 my $brdc = '192.168.229.255'; #指定vip的广播地址 my $ifdev = 'ens33'; #指定vip绑定的网卡 my $key = '1'; #指定vip绑定的虚拟网卡序列号 my $ssh_start_vip = "/sbin/ifconfig ens33:$key $vip"; #代表此变量值为ifconfig ens33:1 192.168.229.200 my $ssh_stop_vip = "/sbin/ifconfig ens33:$key down"; #代表此变量值为ifconfig ens33:1 192.168.229.200 down my $exit_code = 0; #指定退出状态码为0 #my $ssh_start_vip = "/usr/sbin/ip addr add $vip/24 brd $brdc dev $ifdev label $ifdev:$key;/usr/sbin/arping -q -A -c 1 -I $ifdev $vip;iptables -F;"; #my $ssh_stop_vip = "/usr/sbin/ip addr del $vip/24 dev $ifdev label $ifdev:$key"; ################################################################################## GetOptions( 'command=s' => \$command, 'ssh_user=s' => \$ssh_user, 'orig_master_host=s' => \$orig_master_host, 'orig_master_ip=s' => \$orig_master_ip, 'orig_master_port=i' => \$orig_master_port, 'new_master_host=s' => \$new_master_host, 'new_master_ip=s' => \$new_master_ip, 'new_master_port=i' => \$new_master_port, ); exit &main(); sub main { print "\n\nIN SCRIPT TEST====$ssh_stop_vip==$ssh_start_vip===\n\n"; if ( $command eq "stop" || $command eq "stopssh" ) { my $exit_code = 1; eval { print "Disabling the VIP on old master: $orig_master_host \n"; &stop_vip(); $exit_code = 0; }; if ($@) { warn "Got Error: $@\n"; exit $exit_code; } exit $exit_code; } elsif ( $command eq "start" ) { my $exit_code = 10; eval { print "Enabling the VIP - $vip on the new master - $new_master_host \n"; &start_vip(); $exit_code = 0; }; if ($@) { warn $@; exit $exit_code; } exit $exit_code; } elsif ( $command eq "status" ) { print "Checking the Status of the script.. OK \n"; exit 0; } else { &usage(); exit 1; } } sub start_vip() { `ssh $ssh_user\@$new_master_host \" $ssh_start_vip \"`; } ## A simple system call that disable the VIP on the old_master sub stop_vip() { `ssh $ssh_user\@$orig_master_host \" $ssh_stop_vip \"`; } sub usage { print "Usage: master_ip_failover --command=start|stop|stopssh|status --orig_master_host=host --orig_master_ip=ip --orig_master_port=port --new_master_host=host --new_master_ip=ip --new_master_port=port\n"; } (4)创建 MHA 软件目录并拷贝配置文件，这里使用app1.cnf配置文件来管理 mysql 节点服务器
mkdir /etc/masterha
cp /opt/mha4mysql-manager-0.57/samples/conf/app1.cnf /etc/masterha
vim /etc/masterha/app1.cnf#删除原有内容，直接复制并修改节点服务器的IP地址
[server default]
manager_log=/var/log/masterha/app1/manager.log
manager_workdir=/var/log/masterha/app1
master_binlog_dir=/usr/local/mysql/data
master_ip_failover_script=/usr/local/bin/master_ip_failover
master_ip_online_change_script=/usr/local/bin/master_ip_online_change
password=manager
ping_interval=1
remote_workdir=/tmp
repl_password=12345
repl_user=myslave
secondary_check_script=/usr/local/bin/masterha_secondary_check -s 192.168.229.80 -s 192.168.229.70
shutdown_script=""
ssh_user=root
user=mha
[server1]
hostname=192.168.229.90
port=3306
[server2]
candidate_master=1
check_repl_delay=0
hostname=192.168.229.80
port=3306
[server3]
hostname=192.168.229.70
port=3306
-------------------------------解释---------------------------------------------------------------------------
[server default]
manager_log=/var/log/masterha/app1/manager.log #manager日志
manager_workdir=/var/log/masterha/app1.log #manager工作目录 master_binlog_dir=/usr/local/mysql/data/ #master保存binlog的位置，这里的路径要与master里配置的binlog的路径一致，以便MHA能找到 master_ip_failover_script=/usr/local/bin/master_ip_failover #设置自动failover时候的切换脚本，也就是上面的那个脚本 master_ip_online_change_script=/usr/local/bin/master_ip_online_change #设置手动切换时候的切换脚本 password=manager #设置mysql中root用户的密码，这个密码是前文中创建监控用户的那个密码 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failover remote_workdir=/tmp #设置远端mysql在发生切换时binlog的保存位置 repl_password=12345 #设置复制用户的密码 repl_user=myslave #设置复制用户的用户 report_script=/usr/local/send_report #设置发生切换后发送的报警的脚本 secondary_check_script=/usr/local/bin/masterha_secondary_check -s 192.168.229.80 -s 192.168.229.70 #指定检查的从服务器IP地址 shutdown_script="" #设置故障发生后关闭故障主机脚本(该脚本的主要作用是关闭主机防止发生脑裂,这里没有使用) ssh_user=root #设置ssh的登录用户名 user=mha #设置监控用户root [server1] hostname=192.168.229.90 port=3306 [server2] hostname=192.168.229.80 port=3306 candidate_master=1 #设置为候选master，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，即使这个从库不是集群中最新的slave check_repl_delay=0 #默认情况下如果一个slave落后master 超过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 [server3] hostname=192.168.229.70 port=3306 10．第一次配置需要在 Master 节点上手动开启虚拟IP
/sbin/ifconfig ens33:1 192.168.229.200/2411、在 manager 节点上测试 ssh 无密码认证，如果正常最后会输出 successfully，如下所示。
masterha_check_ssh-conf=/etc/masterha/app1.cnf Tue Nov 26 23:09:45 2020 - [warning] Global configuration file /etc/masterha_default.cnf not found. Skipping. Tue Nov 26 23:09:45 2020 - [info] Reading application default configuration from /etc/masterha/app1.cnf.. Tue Nov 26 23:09:45 2020 - [info] Reading server configuration from /etc/masterha/app1.cnf.. Tue Nov 26 23:09:45 2020 - [info] Starting SSH connection tests.. Tue Nov 26 23:09:46 2020 - [debug] Tue Nov 26 23:09:45 2020 - [debug] Connecting via SSH from root@192.168.229.80(192.168.229.80:22) to root@192.168.229.70(192.168.229.70:22).. Tue Nov 26 23:09:46 2020 - [debug] ok. Tue Nov 26 23:09:47 2020 - [debug] Tue Nov 26 23:09:46 2020 - [debug] Connecting via SSH from root@192.168.229.80(192.168.229.80:22) to root@192.168.229.70(192.168.229.70:22).. Tue Nov 26 23:09:47 2020 - [debug] ok. Tue Nov 26 23:09:47 2020 - [info] All SSH connection tests passed successfully. 12、在 manager 节点上测试 mysql 主从连接情况，最后出现 MySQL Replication Health is OK 字样说明正常。如下所示。
masterha_check_repl -conf=/etc/masterha/app1.cnf
[root@192 masterha]# masterha_check_ssh -conf=/etc/masterha/app1.cnf Tue Sep 7 12:51:38 2021 - [warning] Global configuration file /etc/masterha_default.cnf not found. Skipping. Tue Sep 7 12:51:38 2021 - [info] Reading application default configuration from /etc/masterha/app1.cnf.. Tue Sep 7 12:51:38 2021 - [info] Reading server configuration from /etc/masterha/app1.cnf.. Tue Sep 7 12:51:38 2021 - [info] Starting SSH connection tests.. Tue Sep 7 12:51:39 2021 - [debug] Tue Sep 7 12:51:38 2021 - [debug] Connecting via SSH from root@192.168.229.90(192.168.229.90:22) to root@192.168.229.80(192.168.229.80:22).. Tue Sep 7 12:51:38 2021 - [debug] ok. Tue Sep 7 12:51:38 2021 - [debug] Connecting via SSH from root@192.168.229.90(192.168.229.90:22) to root@192.168.229.70(192.168.229.70:22).. Tue Sep 7 12:51:38 2021 - [debug] ok. Tue Sep 7 12:51:39 2021 - [debug] Tue Sep 7 12:51:38 2021 - [debug] Connecting via SSH from root@192.168.229.80(192.168.229.80:22) to root@192.168.229.90(192.168.229.90:22).. Tue Sep 7 12:51:38 2021 - [debug] ok. Tue Sep 7 12:51:38 2021 - [debug] Connecting via SSH from root@192.168.229.80(192.168.229.80:22) to root@192.168.229.70(192.168.229.70:22).. Tue Sep 7 12:51:39 2021 - [debug] ok. Tue Sep 7 12:51:40 2021 - [debug] Tue Sep 7 12:51:39 2021 - [debug] Connecting via SSH from root@192.168.229.70(192.168.229.70:22) to root@192.168.229.90(192.168.229.90:22).. Tue Sep 7 12:51:39 2021 - [debug] ok. Tue Sep 7 12:51:39 2021 - [debug] Connecting via SSH from root@192.168.229.70(192.168.229.70:22) to root@192.168.229.80(192.168.229.80:22).. Tue Sep 7 12:51:39 2021 - [debug] ok. Tue Sep 7 12:51: