一、架构说明
MHA（Master High Availability）是一个用于 MySQL 主从复制管理和自动故障转移的开源工具集。MHA 的主要目的是提供 MySQL 环境的高可用性和自动故障转移功能，确保在主库发生故障时能够快速切换到备库，降低业务中断时间。
MHA 主要由以下几个组件组成：
1.Manager：管理节点，负责监控主库的状态，并处理自动故障转移。Manager 会不断检查数据库的主从同步状态，当主库发生故障时，会自动将备库提升为新的主库，并重新配置其他从库的复制关系。
如果主从延迟，则等待所有relay log全部应用后，将VIP漂移到新主库上，整个故障转移过程对应用程序完全透明。
2.Node：节点，即 MySQL 实例。MHA 通过在每个 MySQL 实例上部署 MHA 脚本来对节点进行监控和操作。
3.SSH：MHA 使用 SSH 协议来进行节点之间的通信和操作。确保在使用 MHA 之前，通过 SSH 配置了节点之间的互信。
MHA 的工作流程通常如下：
1.Manager 通过 SSH 登录到节点上监控 MySQL 主库的状态，包括主从复制延迟、节点健康状况等。
2.当发现主库发生故障或不可用时，Manager 会触发自动故障转移流程，将备库晋升为新的主库。
3.Manager 会更新其他从库的复制关系，确保它们能够正确复制新的主库。
主从复制（一主一从） + 增强半同步 + GTID + MHA（ping_type=INSERT）
| 架构 | 操作系统 | IP | VIP | 主机名 | 服务版本 | 端口 | 磁盘空间 | 内存 | CPU |
|---|---|---|---|---|---|---|---|---|---|
| MHA | redhat7.9 | 192.168.111.34 | 192.168.111.36 | mha-master01 | mysql-8.0.35、manager-0.58、node-0.58 | 3307 | 20G | 4G | 8C |
| – | – | 192.168.111.35 | 192.168.111.36 | mha-slave01 | mysql-8.0.35、manager-0.58、node-0.58 | 3307 | 20G | 4G | 8C |
注：该方案仅支持一主一从
缺点：
1.manager管理节点存在单点故障
2. io_threads异常或者延迟时，有丢失数据的风险（主要由网络故障引发，所以主从节点必须在同一个网段)
二、环境准备
2.1 环境准备、搭建主从在此链接跳转
删除依赖冲突yum remove mariadb*注意：搭建MHA需要的依赖包如下（两个节点都安装）
perl依赖
yum -y install perl-Module-Install perl-Module-BuildMySQL驱动
yum -y install perl-DBD-MySQL perl-Config-Tiny perl-Log-Dispatch perl-Parallel-ForkManageryum install perl-Class-Load perl-MIME-Lite perl-Mail-Send perl-Mail-Sender perl-Mail-Sendmail perl-Params-Validate perl-Sys-Syslog perl-Email-Date-Format perl-MIME-Types以上依赖包如果yum源没有则手动下载安装，依赖包可在以下网址搜索perl-DBD-MySQL-4.023-6.el7.x86_64perl-Config-Tiny-2.14-7.el7.noarchperl-Log-Dispatch-2.41-1.el7.1.noarchperl-Parallel-ForkManager-1.18-2.el7.noarchperl-MIME-Lite-3.030-1.el7.noarchperl-Mail-Sender-0.8.23-1.el7.noarchperl-Mail-Sendmail-0.79-21.el7.noarchperl-Email-Date-Format-1.002-15.el7.noarchperl-MIME-Types-1.38-2.el7.noarch若出现libmysqlclient.so.18报错问题以下是解决方式。
https://rpm.pbone.net/wget ftp://ftp.pbone.net/mirror/download.fedora.redhat.com/pub/fedora/epel/7/aarch64/Packages/p/perl-Log-Dispatch-2.41-1.el7.1.noarch.rpmwget ftp://ftp.pbone.net/mirror/archive.fedoraproject.org/epel/7.2020-10-05/x86_64/Packages/p/perl-Parallel-ForkManager-1.18-2.el7.noarch.rpmwget ftp://ftp.pbone.net/mirror/archive.fedoraproject.org/epel/7.2020-10-05/ppc64/Packages/p/perl-MIME-Lite-3.030-1.el7.noarch.rpmwget ftp://ftp.pbone.net/mirror/archive.fedoraproject.org/epel/7.2019-05-29/ppc64le/Packages/p/perl-Mail-Sender-0.8.23-1.el7.noarch.rpmwget ftp://ftp.pbone.net/mirror/download.fedora.redhat.com/pub/fedora/epel/7/aarch64/Packages/p/perl-Mail-Sendmail-0.79-21.el7.noarch.rpmwget ftp://ftp.pbone.net/mirror/download.fedora.redhat.com/pub/fedora/epel/7/ppc64le/Packages/p/perl-Email-Date-Format-1.002-15.el7.noarch.rpmwget ftp://ftp.pbone.net/mirror/archive.fedoraproject.org/epel/7.2020-04-20/x86_64/Packages/p/perl-MIME-Types-1.38-2.el7.noarch.rpm安装mysql驱动wget ftp://ftp.pbone.net/mirror/dev.mysql.com/pub/Downloads/MySQL-8.0/mysql-community-libs-8.0.28-1.el7.x86_64.rpmwget ftp://ftp.pbone.net/mirror/dev.mysql.com/pub/Downloads/MySQL-8.0/mysql-community-common-8.0.28-1.el7.x86_64.rpmwget ftp://ftp.pbone.net/mirror/dev.mysql.com/pub/Downloads/MySQL-8.0/mysql-community-libs-compat-8.0.28-1.el7.x86_64.rpmwget ftp://ftp.pbone.net/mirror/dev.mysql.com/pub/Downloads/MySQL-8.0/mysql-community-client-plugins-8.0.28-1.el7.x86_64.rpmwget ftp://ftp.pbone.net/mirror/dev.mysql.com/pub/Downloads/MySQL-5.6/MySQL-shared-5.6.51-1.el7.x86_64.rpmwget ftp://ftp.pbone.net/mirror/dev.mysql.com/pub/Downloads/MySQL-8.0/mysql-community-client-plugins-8.0.28-1.el7.x86_64.rpmrpm -ivh mysql-community-common-8.0.28-1.el7.x86_64.rpmrpm -ivh mysql-community-client-plugins-8.0.28-1.el7.x86_64.rpmrpm -ivh mysql-community-libs-8.0.28-1.el7.x86_64.rpmrpm -ivh mysql-community-libs-compat-8.0.28-1.el7.x86_64.rpmrpm -ivh MySQL-shared-5.6.51-1.el7.x86_64.rpm 与mysql-community-libs 互补2.2 数据库用户权限管理
2.2.1 权限管理
在主从环境按照以下建议赋予权限，禁止赋予all privileges权限
普通用户DDL权限控制
管理员账号，账号名统一为admin_root,由项目负责人管理，用于数据初始化等临时操作
create user 'admin_root'@'%' identified by 'myttrepl@2222#TO'; grant alter,Alter routine,Create,Create routine,Create view,Delete,Drop,Select,Insert,Show view,Update on *.* to 'admin_root'@'%';grant Event,Execute,Index,Lock tables,Process,References,Reload,Show databases,Trigger on *.* to 'admin_root'@'%';应用账号权限
#无特殊需求是，默认赋予以下权限
create user 'app_du'@'%' identified by 'myttrepl@2222#TO'; grant select,update,delete,insert,Show view,Trigger,Execute,Alter routine on db.* to 'app_du'@'%';grant event on *.* to 'app_du'@'%';如果主库宕机后，能够快速上线，要避免业务写从库，这样主库可以以slave身份重新加入，并保持数据同步。
处理方式：不给业务分配超级权限账号，就可以避免从库写入（因为从库始终处于read_only模式）
2.3 配置互信
方法1：使用ssh-copy命令配置（分别在2个节点执行）
ssh-keygen -t rsassh-copy-id -i /root/.ssh/id_rsa.pub root@192.168.111.34ssh-copy-id -i /root/.ssh/id_rsa.pub root@192.168.111.35方法2：手工配置
执行ssh-keygen -t rsa生成一对密钥
然后将公钥（id_rsa.pub）分别写入34、35两台机器的/root/.ssh/authorized_keys中
测试是否成功
ssh 192.168.111.34 date&& ssh 192.168.111.35 date三、安装MHA
3.1 创建目录
mkdir -p /data/mha/{scripts,conf,manager}3.2 配置在线切换、故障切换检测脚本
vi /data/mha/scripts/master_ip_failover_vip需要修改的地方my $vip = '192.168.111.36/24';my $ssh_start_vip = "/usr/sbin/ifconfig ens32:$key $vip";my $ssh_stop_vip = "/usr/sbin/ifconfig ens32:$key down";#!/usr/bin/env perluse 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); my $vip = '192.168.111.36/24';my $key = '1';my $ssh_start_vip = "/sbin/ifconfig ens32:$key $vip";my $ssh_stop_vip = "/sbin/ifconfig ens32:$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" ) { 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 \" $ssh_start_vip \"`;}sub stop_vip() { return 0unless($ssh_user);`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";}vi /data/mha/scripts/master_ip_online_change_vip需要修改的地方my $vip = '192.168.111.36/24';my $ssh_start_vip = "/usr/sbin/ifconfig ens32:$key $vip";my $ssh_stop_vip = "/usr/sbin/ifconfig ens32:$key down";#!/usr/bin/env perluse strict;use warnings FATAL =>'all';use Getopt::Long; my $vip = '192.168.111.36/24';# Virtual IPmy $key = "1";my $ssh_start_vip = "/sbin/ifconfig ens32:$key $vip";my $ssh_stop_vip = "/sbin/ifconfig ens32:$key down";my $exit_code = 0;my ($command,$orig_master_is_new_slave, $orig_master_host,$orig_master_ip, $orig_master_port, $orig_master_user,$orig_master_password, $orig_master_ssh_user, $new_master_host,$new_master_ip,$new_master_port,$new_master_user,$new_master_password,$new_master_ssh_user,);GetOptions('command=s'=> \$command,'orig_master_is_new_slave' => \$orig_master_is_new_slave,'orig_master_host=s' => \$orig_master_host,'orig_master_ip=s' => \$orig_master_ip,'orig_master_port=i' => \$orig_master_port,'orig_master_user=s' => \$orig_master_user,'orig_master_password=s' => \$orig_master_password,'orig_master_ssh_user=s' => \$orig_master_ssh_user,'new_master_host=s'=> \$new_master_host,'new_master_ip=s'=> \$new_master_ip,'new_master_port=i'=> \$new_master_port,'new_master_user=s'=> \$new_master_user,'new_master_password=s'=> \$new_master_password,'new_master_ssh_user=s'=> \$new_master_ssh_user,);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 "\n\n\n***************************************************************\n";print "Disabling the VIP - $vip on old master: $orig_master_host\n";print "***************************************************************\n\n\n\n";&stop_vip();$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 "\n\n\n***************************************************************\n";print "Enabling the VIP - $vip on new master: $new_master_host \n";print "***************************************************************\n\n\n\n";&start_vip();$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 $orig_master_ssh_user\@$orig_master_host \" $ssh_start_vip \"`;exit 0;}else {&usage();exit 1;}}# A simple system call that enable the VIP on the new mastersub start_vip() {`ssh $new_master_ssh_user\@$new_master_host \" $ssh_start_vip \"`;}# A simple system call that disable the VIP on the old_mastersub stop_vip() {`ssh $orig_master_ssh_user\@$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";}chmod +x /data/mha/scripts/master_ip_failover_vipchmod +x /data/mha/scripts/master_ip_online_change_vip3.3 安装MHA软件
mha4mysql-node-0.58.tar.gz —> 两节点都安装
mha4mysql-manager-0.58.tar.gz —> 两节点都安装
cd /data/mhawget https://github.com/yoshinorim/mha4mysql-node/releases/download/v0.58/mha4mysql-node-0.58.tar.gzwget https://github.com/yoshinorim/mha4mysql-manager/releases/download/v0.58/mha4mysql-manager-0.58.tar.gztar -zxvf mha4mysql-node-0.58.tar.gzcd mha4mysql-node-0.58perl Makefile.PLmake && make installln -s /data/mha/mha4mysql-node-0.58/bin/* /usr/local/bin/ll /usr/local/bin/tar -zxvf mha4mysql-manager-0.58.tar.gzcd mha4mysql-manager-0.58perl Makefile.PLmake && make installln -s /data/mha/mha4mysql-manager-0.58/bin/* /usr/local/bin/ll /usr/local/bin/3.4 在manager节点配置masterha.cnf、app.cnf（两个节点都配置）
创建mha管理账号(仅在节点1创建)
create user 'i_mha'@'192.168.%.%' identified by "myttrepl@2222#TO";GRANT ALL PRIVILEGES ON *.* TO 'i_mha'@'192.168.%.%' with grant option;mkdir -p /data/mha/masterha/vi /data/mha/conf/masterha.cnf[server default]user=i_mha#设置监控用户mhapassword=myttrepl@2222#TO#设置mysql中mha用户的密码，这个密码是前文中创建监控用户的那个密码repl_user=repl#设置复制用户的用户replrepl_password=myttrepl@2222#TO#设置复制用户repl的密码ssh_user=root#设置ssh的登录用户名ping_interval=10#设置监控主库，发送ping包的时间间隔10秒，默认是3秒，尝试三次没有回应的时候自动进行failoverping_type=CONNECTremote_workdir=/data/mha/masterha/#manager工作目录vi /data/mha/conf/app.cnfmanager_workdir=/data/mha/manager/#manager工作目录manager_log=/data/mha/manager/manager.log#manager日志#workdir on the node for mysql servermaster_binlog_dir=/data/mysql8.0.35/3307/binlog/#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#自动故障切换master脚本master_ip_failover_script=/data/mha/scripts/master_ip_failover_vip#手动切换时运行的脚本master_ip_online_change_script= /data/mha/scripts/master_ip_online_change_vip#指定检查的从服务器IP地址secondary_check_script = /usr/local/bin/masterha_secondary_check -s 192.168.111.34 -s 192.168.111.35[server1]hostname=192.168.111.34ssh_port=22port=3307#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，即使这个主库不是集群中最新的slavecandidate_master=1#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mastercheck_repl_delay=0 #忽略relay logs日志的复制延迟[server2]hostname=192.168.111.35ssh_port=22port=3307candidate_master=1check_repl_delay=03.5 检测互信
[root@mhaserver01 conf]# masterha_check_ssh --global_conf=/data/mha/conf/masterha.cnf --conf=/data/mha/conf/app.cnfThu Feb 22 16:34:13 2024 - [warning] Global configuration file /etc/masterha_default.cnf not found. Skipping.Thu Feb 22 16:34:13 2024 - [info] Reading application default configuration from /data/mha/conf/app.cnf..Thu Feb 22 16:34:13 2024 - [info] Reading server configuration from /data/mha/conf/app.cnf..Thu Feb 22 16:34:13 2024 - [info] Starting SSH connection tests..Thu Feb 22 16:34:13 2024 - [debug]Thu Feb 22 16:34:13 2024 - [debug]Connecting via SSH from root@192.168.111.34(192.168.111.34:22) to root@192.168.111.35(192.168.111.35:22)..Thu Feb 22 16:34:13 2024 - [debug] ok.Thu Feb 22 16:34:14 2024 - [debug]Thu Feb 22 16:34:13 2024 - [debug]Connecting via SSH from root@192.168.111.35(192.168.111.35:22) to root@192.168.111.34(192.168.111.34:22)..Thu Feb 22 16:34:14 2024 - [debug] ok.Thu Feb 22 16:34:14 2024 - [info] All SSH connection tests passed successfully.3.6 检测主从状态
[root@mhaserver01 conf]# masterha_check_repl --global_conf=/data/mha/conf/masterha.cnf --conf=/data/mha/conf/app.cnfFri Feb 23 10:50:09 2024 - [warning] Global configuration file /etc/masterha_default.cnf not found. Skipping.Fri Feb 23 10:50:09 2024 - [info] Reading application default configuration from /data/mha/conf/app.cnf..Fri Feb 23 10:50:09 2024 - [info] Reading server configuration from /data/mha/conf/app.cnf..Fri Feb 23 10:50:09 2024 - [info] MHA::MasterMonitor version 0.58.Fri Feb 23 10:50:10 2024 - [info] GTID failover mode = 1Fri Feb 23 10:50:10 2024 - [info] Dead Servers:Fri Feb 23 10:50:10 2024 - [info] Alive Servers:Fri Feb 23 10:50:10 2024 - [info] 192.168.111.34(192.168.111.34:3307)Fri Feb 23 10:50:10 2024 - [info] 192.168.111.35(192.168.111.35:3307)Fri Feb 23 10:50:10 2024 - [info] Alive Slaves:Fri Feb 23 10:50:10 2024 - [info] 192.168.111.35(192.168.111.35:3307)Version=8.0.35 (oldest major version between slaves) log-bin:enabledFri Feb 23 10:50:10 2024 - [info] GTID ONFri Feb 23 10:50:10 2024 - [info] Replicating from 192.168.111.34(192.168.111.34:3307)Fri Feb 23 10:50:10 2024 - [info] Primary candidate for the new Master (candidate_master is set)Fri Feb 23 10:50:10 2024 - [info] Current Alive Master: 192.168.111.34(192.168.111.34:3307)Fri Feb 23 10:50:10 2024 - [info] Checking slave configurations..Fri Feb 23 10:50:10 2024 - [info]read_only=1 is not set on slave 192.168.111.35(192.168.111.35:3307).Fri Feb 23 10:50:10 2024 - [info] Checking replication filtering settings..Fri Feb 23 10:50:10 2024 - [info]binlog_do_db= , binlog_ignore_db=Fri Feb 23 10:50:10 2024 - [info]Replication filtering check ok.Fri Feb 23 10:50:10 2024 - [info] GTID (with auto-pos) is supported. Skipping all SSH and Node package checking.Fri Feb 23 10:50:10 2024 - [info] Checking SSH publickey authentication settings on the current master..Fri Feb 23 10:50:11 2024 - [info] HealthCheck: SSH to 192.168.111.34 is reachable.Fri Feb 23 10:50:11 2024 - [info]192.168.111.34(192.168.111.34:3307) (current master) +--192.168.111.35(192.168.111.35:3307)Fri Feb 23 10:50:11 2024 - [info] Checking replication health on 192.168.111.35..Fri Feb 23 10:50:11 2024 - [info]ok.Fri Feb 23 10:50:11 2024 - [info] Checking master_ip_failover_script status:Fri Feb 23 10:50:11 2024 - [info] /data/mha/scripts/master_ip_failover_vip --command=status --ssh_user=root --orig_master_host=192.168.111.34 --orig_master_ip=192.168.111.34 --orig_master_port=3307IN SCRIPT TEST====/usr/sbin/ifconfig ens32:1 down==/usr/sbin/ifconfig ens32:1 192.168.111.36/24===Checking the Status of the script.. OKFri Feb 23 10:50:11 2024 - [info]OK.Fri Feb 23 10:50:11 2024 - [warning] shutdown_script is not defined.Fri Feb 23 10:50:11 2024 - [info] Got exit code 0 (Not master dead).MySQL Replication Health is OK.3.7 开启MHA-manager监控进程（mhamaster02启用manager管理）
注意：第一次启动，主库上的VIP 不会自动绑定，需要手动去绑定，主库发生故障切换会进行vip的漂移
#起服务nohup masterha_manager --global_conf=/data/mha/conf/masterha.cnf--conf=/data/mha/conf/app.cnf --ignore_last_failover /data/mha/run.log 2>&1 start slave;//启动slave进程 --查看slave状态确认IO线程、SQL线程都以运行mysql> show slave status\G;//查看当前的从库状态Slave_IO_Running: Yes//IO线程已运行 Slave_SQL_Running: Yes//SQL线程已运行mysql> show slave status\G;//查看当前的从库状态4.2.4 主库启动manager服务并查看MHA状态
nohup masterha_manager --global_conf=/data/mha/conf/masterha.cnf--conf=/data/mha/conf/app.cnf --ignore_last_failover /data/mha/run.log 2>&1 &masterha_check_status --global_conf=/data/mha/conf/masterha.cnf--conf=/data/mha/conf/app.cnfapp (pid:14837) is running(0:PING_OK), master:192.168.111.34五、MHA 日常维护命令集：
1 查看ssh 登陆是否成功
masterha_check_ssh --global_conf=/data/mha/conf/masterha.cnf --conf=/data/mha/conf/app.cnf2 查看主从同步情况
masterha_check_repl--global_conf=/data/mha/conf/masterha.cnf --conf=/data/mha/conf/app.cnf3 检查启动的状态
masterha_check_status--global_conf=/data/mha/conf/masterha.cnf --conf=/data/mha/conf/app.cnf4 停止mha
masterha_stop --global_conf=/data/mha/conf/masterha.cnf --conf=/data/mha/conf/app.cnf5 启动mha
nohup masterha_manager --global_conf=/data/mha/conf/masterha.cnf--conf=/data/mha/conf/app.cnf --ignore_last_failover /data/mha/run.log 2>&1 &注意：当有slave 节点宕掉的情况是启动不了的，加上–ignore_fail_on_start 即使有节点宕掉也能启动mha，需要在配置文件中设置ignore_fail=1
6 failover 后下次重启
每次failover 切换后会在管理目录生成文件app.failover.complete ，下次在切换的时候会发现有这个文件导致切换不成功，需要手动清理掉。rm -rf /masterha/app1/app1.failover.complete也可以加上参数--ignore_last_failover7 手工failover
手工failover 场景，master 死掉，但是masterha_manager 没有开启，可以通过手工failover：masterha_master_switch --global_conf=/data/mha/conf/masterha.cnf--conf=/data/mha/conf/app.cnf --dead_master_host=old_ip --dead_port=port --master_state=dead --new_master_host=new_ip --new_master_port=port --ignore_last_failover8 masterha_manager 是一种监视和故障转移的程序。另一方面,masterha_master_switch 程序不监控主库。masterha_master_switch 可以用于主库故障转移,也可用于在线总开关。
9 手动在线切换(比如做维护切换时)
masterha_master_switch ---global_conf=/data/mha/conf/masterha.cnf--conf=/data/mha/conf/app.cnf --master_state=alive --new_master_host=192.168.111.34 --orig_master_is_new_slave或者masterha_master_switch --global_conf=/data/mha/conf/masterha.cnf--conf=/data/mha/conf/app.cnf --master_state=alive --new_master_host=192.168.111.34 -orig_master_is_new_slave --running_updates_limit=10000--orig_master_is_new_slave 切换时加上此参数是将原master 变为slave 节点，如果不加此参数，原来的master 将不启动--running_updates_limit=10000 切换时候选master 如果有延迟的话，mha 切换不能成功，加上此参数表示延迟在此时间范围内都可切换（单位为s），但是切换的时间长短是由recover时relay 日志的大小决定手动在线切换mha，切换时需要将在运行的mha 停掉后才能切换。在备库先执行DDL，一般先stop slave，一般不记录mysql 日志，可以通过set SQL_LOG_BIN =0 实现。然后进行一次主备切换操作，再在原来的主库上执行DDL。这种方法适用于增减索引，如果是增加字段就需要额外注意。