MySQL 高可用之MHA 工作原理和架构，实现MHA高可用实战案例_mha4mysql-manager

1 MHA 工作原理和架构

MHA集群架构

MHA工作原理

1. MHA利用 SELECT 1 As Value 指令判断master服务器的健康性,一旦master 宕机,MHA 从宕机崩溃
   的master保存二进制日志事件（binlog events）
2. 识别含有最新更新的slave
3. 应用差异的中继日志（relay log）到其他的slave
4. 应用从master保存的二进制日志事件（binlog events）
5. 提升一个slave为新的master
6. 使其他的slave连接新的master进行复制

MHA软件
MHA软件由两部分组成，Manager工具包和Node工具包
Manager工具包主要包括以下几个工具：

**Node工具包：**这些工具通常由MHA Manager的脚本触发，无需人为操作）主要包括以下几个工具：

MHA自定义扩展：

MHA配置文件：
global配置，为各application提供默认配置，默认文件路径 /etc/masterha_default.cnf
application配置：为每个主从复制集群

2 实现 MHA 实战案例

环境:四台主机

• 192.168.100.120 CentOS7 MHA管理端
• 192.168.100.104 CentOS8 MySQL8.0 Master
• 192.168.100.105 CentOS8 MySQL8.0 Slave1
• 192.168.100.106 CentOS8 MySQL8.0 Slave2

2.1 在管理节点上安装两个包mha4mysql-manager和mha4mysql-node

mha4mysql-manager和mha4mysql-node安装包：

链接：https://pan.baidu.com/s/1BvaQBQEdx-9N3w1fy3YnTA?pwd=grc0 提取码：grc0

[root@mha-manager ~]#yum -y install mha4mysql-manager-0.58-0.el7.centos.noarch.rpm
[root@mha-manager ~]#yum -y install mha4mysql-node-0.58-0.el7.centos.noarch.rpm
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2.2 在所有MySQL服务器上安装mha4mysql-node包

[root@master ~]#yum -y install mha4mysql-node-0.58-0.el7.centos.noarch.rpm
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2.3 在所有节点实现相互之间ssh key验证

[root@mha-manager ~]#ssh-keygen
[root@mha-manager ~]#ssh-copy-id 127.0.0.1
[root@mha-manager ~]#rsync -av .ssh 192.168.100.104:/root/
[root@mha-manager ~]#rsync -av .ssh 192.168.100.105:/root/
[root@mha-manager ~]#rsync -av .ssh 192.168.100.106:/root/
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2.4 在管理节点建立配置文件

[root@mha-manager ~]#mkdir /etc/mastermha/
[root@mha-manager ~]#vim /etc/mastermha/app1.cnf
[server default]
user=mhauser
password=magedu
manager_workdir=/data/mastermha/app1/
manager_log=/data/mastermha/app1/manager.log
remote_workdir=/data/mastermha/app1/
ssh_user=root
repl_user=repluser
repl_password=123456
ping_interval=1
master_ip_failover_script=/usr/local/bin/master_ip_failover
report_script=/usr/local/bin/sendmail.sh
check_repl_delay=0
master_binlog_dir=/data/mysql/
[server1]
hostname=192.168.100.104
candidate_master=1
[server2]
hostname=192.168.100.105
candidate_master=1
[server3]
hostname=192.168.100.106
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2.5 相关脚本

实现邮件通信

yum -y install postfix mailx 
systemctl enable --now postfix 
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vim /etc/mail.rc
#在下面加上
set from=邮箱
set smtp=smtp.qq.com
set smtp-auth-user=邮箱
set smtp-auth-password=授权码
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获取授权码：
再邮箱里面打开IMAP/SMTP服务，获取授权码！

[root@mha-manager ~]#vim /usr/local/bin/sendmail.sh
#!/bin/bash
echo "MySQL is down" | mail -s "MHA Warning" 邮箱
[root@mha-manager ~]#chmod +x /usr/local/bin/sendmail.sh
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[root@mha-manager ~]#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
);
#执行时必须删除下面三行注释
my $vip = '192.168.100.150/24';#设置Virtual IP
my $gateway = '192.168.100.2';#网关Gateway IP
my $interface = 'eth0';    #指定VIP所在网卡
my $key = "1";
my $ssh_start_vip = "/sbin/ifconfig $interface:$key $vip;/sbin/arping -I 
$interface -c 3 -s $vip $gateway >/dev/null 2>&1";
my $ssh_stop_vip = "/sbin/ifconfig $interface:$key down";
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" ) {
# $orig_master_host, $orig_master_ip, $orig_master_port are passed.
# If you manage master ip address at global catalog database,
# invalidate orig_master_ip here.
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" ) {
# all arguments are passed.
# If you manage master ip address at global catalog database,
# activate new_master_ip here.
# You can also grant write access (create user, set read_only=0, etc) here.
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";
`ssh $ssh_user\@$orig_master_host \" $ssh_start_vip \"`;
exit 0;
}
else {
&usage();
exit 1;
}
}
#A simple system call that enable the VIP on the new master
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";
}
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授予执行权限：

[root@mha-manager ~]#chmod +x /usr/local/bin/master_ip_failover
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2.6 实现Master

[root@master ~]#mkdir /data/mysql/
[root@master ~]#chown mysql.mysql /data/mysql/
[root@master ~]#dnf -y install mysql-server
[root@master ~]#vim /etc/my.cnf
[mysqld]
server_id=1
log-bin=/data/mysql/mysql-bin
skip_name_resolve=1
general_log     #观察结果,非必须项,生产无需启用
[root@master ~]#systemctl enable --now mysqld
mysql>show master logs;
mysql>create user repluser@'192.168.100.%' identified by '123456';
mysql>grant replication slave on *.* to repluser@'192.168.100.%' ;
mysql>create user mhauser@'192.168.100.%' identified by '123456';
mysql>grant all on *.* to mhauser@'192.168.100.%' ;
#配置VIP
[root@master ~]#ifconfig eth0:1 192.168.100.150/24
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2.7 实现slave

[root@slave ~]#mkdir /data/mysql
[root@slave ~]#chown mysql.mysql /data/mysql/
[root@slave ~]#dnf -y install mysql-server
[root@slave ~]#vim /etc/my.cnf
[mysqld]
server_id=2   #不同节点此值各不相同
log-bin=/data/mysql/mysql-bin
read_only
relay_log_purge=0
skip_name_resolve=1    #禁止反向解析
general_log  #方便观察的设置,生产无需启用
[root@slave ~]#systemctl enable --now mysqld
mysql>CHANGE MASTER TO MASTER_HOST='MASTER_IP', MASTER_USER='repluser', 
MASTER_PASSWORD='123456', MASTER_LOG_FILE='mysql-bin.000001', 
MASTER_LOG_POS=245;
mysql>START SLAVE;
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2.8 检查MHA的环境

#检查环境

[root@mha-manager ~]#masterha_check_ssh --conf=/etc/mastermha/app1.cnf
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[root@mha-manager ~]#masterha_check_repl --conf=/etc/mastermha/app1.cnf
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#查看状态

[root@mha-manager ~]#masterha_check_status --conf=/etc/mastermha/app1.cnf
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2.9 启动MHA

#开启MHA,默认是前台运行,生产环境一般为后台执行
nohup masterha_manager --conf=/etc/mastermha/app1.cnf &> /dev/null 
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#查看状态
masterha_check_status --conf=/etc/mastermha/app1.cnf  
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2.10 排错日志

tail /data/mastermha/app1/manager.log
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2.11 模拟故障检验

#当 master down机后,mha管理程序自动退出
通过查看日志可以看到主节点（192.168.100.104）已经切换为（192.168.100.105）

tail -f /data/mastermha/app1/manager.log
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#查看状态
masterha_check_status --conf=/etc/mastermha/app1.cnf  
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在192.168.100.105查看开启的进程

可以看到192.168.100.105已经成为主节点

在192.168.100.106查看从节点状态信息

可以看到192.168.100.106的主节点变成了192.168.100.105