背景介绍
高可用架构对于互联网服务基本是标配，无论是应用服务还是数据库服务都需要做到高可用。本文是对MySQL数据库的高可用方案中，基于主从复制的MHA软件理论部分进行梳理和小结。
MHA软件介绍
1.MHA软件是由MHA Manager（管理节点）和MHA Node（数据节点）组成
2.MHA Manager可以单独部署在一台独立的机器上，也可以部署在一台slave节点上
3.MHA Node运行在每台MySQL服务器上
4.MHA Manager会定时探测集群中的master节点，当master出现故障时，自动将数据最新的slave提升为新的master，然后将其他slave重新指向新的master恢复主从复制。
5.整个故障转移过程对应用程序完全透明
MHA架构介绍
1.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
2.在一主两从的MHA集群架构中，一台充当master，一台充当备用master，一台充当slave
3.因为至少需要三台服务器，出于机器成本的考虑，淘宝在该基础上做了改进，目前淘宝TMHA支持一主一从
4.我们自己使用时，也可以使用1主1从，但是master主机宕机后无法切换，以及无法补全binlog。不过，master的mysqld进程crash后，还是可以切换成功，以及补全binlog
MHA切换原理
自动故障切换过程
1.配置文件检查阶段，这个阶段会检查整个集群配置文件配置
2.宕机的master处理，这个阶段包括vip移除操作，主机关机操作
3.复制dead master和最新slave相差的relay log，并保存到MHA Manager定义的目录下
4.识别含有最新更新的slave
5.应用从master保存的二进制日志事件（binlog events）
6.提升一个slave为新的master
7.使其他的slave连接新的master进行复制
手工故障切换过程
注意事项：MHA Manager必须没有运行
1.手工调用MHA进行故障切换，masterha_master_switch
2.在经历配置文件检查、存活服务器检查、集群复制检查、备用master设置检查后，询问master阵亡，是否进行切换
3.宕机的master处理，这个阶段包括vip移除操作，主机关机操作
4.复制dead master和最新slave相差的relay log，并保存到MHA Manager定义的目录下
5.识别含有最新更新的slave
6.应用从master保存的二进制日志事件（binlog events）
7.提升一个slave为新的master
8.使其他的slave连接新的master进行复制
手工在线切换过程
1.检测集群复制设置和确定当前master
2.确定新的master
3.阻塞写入到当前master
4.等待所有slave赶上复制
5.授予写入到新的master
6.重新设置slave从新的master进行复制
本文主要介绍如何搭建MHA集群，希望给你带来帮助
基本环境介绍
Linux：CentOS 7.4
MySQL：5.7.21+传统复制（开启GTID不搭建binlog server) VIP：192.168.68.100| 角色 | ip地址 | 主机名 | server_id | 类型 |
|---|---|---|---|---|
| Master | 192.168.68.161 | server1 | 1413306 | 写 |
| Candicate master | 192.168.68.162 | server2 | 1423306 | 读 |
| Manager/Slave | 192.168.68.163 | server3 | 1433306 | 读/监控/管理 |
server1
主从复制搭建
#创建复制用户
grant replication slave on *.* to 'repl'@'192.168.68.%' identified by 'repl4slave'; flush privileges; #创建监控用户 grant all privileges on *.* to 'xmm'@'192.168.68.%' identified by 'xmmxmm'; flush privileges;MHA安装
#软件安装
yum localinstall -y mha4mysql-node-0.56-0.el6.noarch #SSH登陆检查 ssh server2 ssh server3如果不是一个新master
#master导出数据
mysqldump --master-data=2 --single-transaction -R --triggers -A >server1-all-180329.sqlVIP手工绑定
绑定：/sbin/ip addr add 192.168.68.100/32 dev ens32 解绑：/sbin/ip addr del 192.168.68.100/32 dev ens32 server2
主从复制搭建
#配置和开启复制
change master to master_host='192.168.68.161',master_port=3306,master_user='repl',master_password='repl4slave',master_auto_position=1; start slave; #slave开启read_only mysql -h127.0.0.1 -p -e 'set global read_only=1' mysql -h127.0.0.1 -p -e 'set global relay_log_purge=0'MHA安装
#软件安装
yum localinstall -y mha4mysql-node-0.56-0.el6.noarch #SSH登陆检查 ssh server1 ssh server3如果master不是新的
#导入数据
mysql -h127.0.0.1 -uroot -p < /tmp/data/server1-all-180329.sqlserver3
主从复制搭建
#导入数据、配置和开启复制
mysql -h127.0.0.1 -uroot -p < /tmp/data/server1-all-180329.sql change master to master_host='192.168.68.135',master_port=3306,master_user='repl',master_password='repl4slave',master_auto_position=1; start slave; #slave开启read_only mysql -h127.0.0.1 -p -e 'set global read_only=1' mysql -h127.0.0.1 -p -e 'set global relay_log_purge=0'MHA安装
#软件安装
yum localinstall -y mha4mysql-node-0.56-0.el6.noarch
yum localinstall -y mha4mysql-manager-0.56-0.el6.noarch #SSH无密钥验证登陆 ssh-keygen cd ~/.ssh/ cat id_rsa.pub > authorized_keys chmod 600 * scp -r ~/.ssh/ root@192.168.68.161:~/ scp -r ~/.ssh/ root@192.168.68.162:~/ ssh server2 ssh server3 #创建MHA工作目录，上传配置文件和脚本 mkdir -p /etc/masterha masterha_default.cnf app1.cnf master_ip_failover master_ip_online_change chmod +x master_ip* #开启debug masterha_default.cnf --> log_level=debug #manager上检查ssh/rple/开启mha进程 masterha_check_ssh xxx masterha_check_repl xxx masterha_manager xxx配置文件和脚本详细
masterha_default.cnf
[server default]
#MySQL的用户和密码
user=xmm
password=xmmxmm
#系统ssh用户 ssh_user=root #复制用户 repl_user=repl repl_password=repl4slave #监控 ping_interval=1 #shutdown_script="" #日志输出 log_level=debug #报警脚本 report_script=/etc/masterha/send_report #切换调用的脚本 master_ip_failover_script= /etc/masterha/master_ip_failover master_ip_online_change_script= /etc/masterha/master_ip_online_changeapp1.cnf
[server default]
#mha manager工作目录
manager_workdir = /var/log/masterha/app1
manager_log = /var/log/masterha/app1/app1.log
remote_workdir = /var/log/masterha/app1 [server1] hostname=node1 master_binlog_dir = /data/mysql/mysql3306/logs candidate_master = 0 check_repl_delay = 0 [server2] hostname=node2 master_binlog_dir=/data/mysql/mysql3306/logs candidate_master = 1 check_repl_delay = 0 [server3] hostname=node1 master_binlog_dir = /data/mysql/mysql3306/logs candidate_master = 0 check_repl_delay = 0master_ip_failover
#!/usr/bin/env perl
# Copyright (C) 2011 DeNA Co.,Ltd.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by # the Free Software Foundation; either version 2 of the License, or # (at your option) any later version. # # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program; if not, write to the Free Software # Foundation, Inc., # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA ## Note: This is a sample script and is not complete. Modify the script based on your environment. use strict; use warnings FATAL => 'all'; use Getopt::Long; use MHA::DBHelper; #自定义该组机器的vip my $vip = "192.168.68.100"; my $if = "ens32"; my ( $command, $ssh_user, $orig_master_host, $orig_master_ip, $orig_master_port, $new_master_host, $new_master_ip, $new_master_port, $new_master_user, $new_master_password ); 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, 'new_master_user=s' => \$new_master_user, 'new_master_password=s' => \$new_master_password, ); sub add_vip { my $output1 = `ssh -o ConnectTimeout=15 -o ConnectionAttempts=3 $orig_master_host /sbin/ip addr del $vip/32 dev $if`; my $output2 = `ssh -o ConnectTimeout=15 -o ConnectionAttempts=3 $new_master_host /sbin/ip addr add $vip/32 dev $if`; } exit &main(); sub main { 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 { # updating global catalog, etc $exit_code = 0; }; if ($@) { 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 { my $new_master_handler = new MHA::DBHelper(); # args: hostname, port, user, password, raise_error_or_not $new_master_handler->connect( $new_master_ip, $new_master_port, $new_master_user, $new_master_password, 1 ); ## Set read_only=0 on the new master $new_master_handler->disable_log_bin_local(); print "Set read_only=0 on the new master.\n"; $new_master_handler->disable_read_only(); ## Creating an app user on the new master #print "Creating app user on the new master..\n"; #FIXME_xxx_create_user( $new_master_handler->{dbh} ); $new_master_handler->enable_log_bin_local(); $new_master_handler->disconnect(); ## Update master ip on the catalog database, etc &add_vip(); $exit_code = 0; }; if ($@) { warn $@; # If you want to continue failover, exit 10. exit $exit_code; } exit $exit_code; } elsif ( $command eq "status" ) { # do nothing exit 0; } else { &usage(); exit 1; } } 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"; }master_ip_online_change
#!/usr/bin/env perl
# Copyright (C) 2011 DeNA Co.,Ltd.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by # the Free Software Foundation; either version 2 of the License, or # (at your option) any later version. # # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program; if not, write to the Free Software # Foundation, Inc., # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA ## Note: This is a sample script and is not complete. Modify the script based on your environment. use strict; use warnings FATAL => 'all'; use Getopt::Long; use MHA::DBHelper; use MHA::NodeUtil; use Time::HiRes qw( sleep gettimeofday tv_interval ); use Data::Dumper; my $_tstart; my $_running_interval = 0.1; #添加vip定义 my $vip = "192.168.68.100"; my $if = "ens32"; 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 drop_vip { my $output = `ssh -o ConnectTimeout=15 -o ConnectionAttempts=3 $orig_master_host /sbin/ip addr del $vip/32 dev $if`; #mysql里的连接全部干掉 #FIXME } sub add_vip { my $output = `ssh -o ConnectTimeout=15 -o ConnectionAttempts=3 $new_master_host /sbin/ip addr add $vip/32 dev $if`; } sub current_time_us { my ( $sec, $microsec ) = gettimeofday(); my $curdate = localtime($sec); return $curdate . " " . sprintf( "%06d", $microsec ); } sub sleep_until { my $elapsed = tv_interval($_tstart); if ( $_running_interval > $elapsed ) { sleep( $_running_interval - $elapsed ); } } sub get_threads_util { my $dbh = shift; my $my_connection_id = shift; my $running_time_threshold = shift; my $type = shift; $running_time_threshold = 0 unless ($running_time_threshold); $type = 0 unless ($type); my @threads; my $sth = $dbh->prepare("SHOW PROCESSLIST"); $sth->execute(); while ( my $ref = $sth->fetchrow_hashref() ) { my $id = $ref->{Id}; my $user = $ref->{User}; my $host = $ref->{Host}; my $command = $ref->{Command}; my $state = $ref->{State}; my $query_time = $ref->{Time}; my $info = $ref->{Info}; $info =~ s/^\s*(.*?)\s*$/$1/ if defined($info); next if ( $my_connection_id == $id ); next if ( defined($query_time) && $query_time < $running_time_threshold ); next if ( defined($command) && $command eq "Binlog Dump" ); next if ( defined($user) && $user eq "system user" ); next if ( defined($command) && $command eq "Sleep" && defined($query_time) && $query_time >= 1 ); if ( $type >= 1 ) { next if ( defined($command) && $command eq "Sleep" ); next if ( defined($command) && $command eq "Connect" ); } if ( $type >= 2 ) { next if ( defined($info) && $info =~ m/^select/i ); next if ( defined($info) && $info =~ m/^show/i ); } push @threads, $ref; } return @threads; } sub main { if ( $command eq "stop" ) { ## Gracefully killing connections on the current master # 1. Set read_only= 1 on the new master # 2. DROP USER so that no app user can establish new connections # 3. Set read_only= 1 on the current master # 4. Kill current queries # * Any database access failure will result in script die. my $exit_code = 1; eval { ## Setting read_only=1 on the new master (to avoid accident) my $new_master_handler = new MHA::DBHelper(); # args: hostname, port, user, password, raise_error(die_on_error)_or_not $new_master_handler->connect( $new_master_ip, $new_master_port, $new_master_user, $new_master_password, 1 ); print current_time_us() . " Set read_only on the new master.. "; $new_master_handler->enable_read_only(); if ( $new_master_handler->is_read_only() ) { print "ok.\n"; } else { die "Failed!\n"; } $new_master_handler->disconnect(); # Connecting to the orig master, die if any database error happens my $orig_master_handler = new MHA::DBHelper(); $orig_master_handler->connect( $orig_master_ip, $orig_master_port, $orig_master_user, $orig_master_password, 1 ); ## Drop application user so that nobody can connect. Disabling per-session binlog beforehand $orig_master_handler->disable_log_bin_local(); # print current_time_us() . " Drpping app user on the orig master..\n"; print current_time_us() . " drop vip $vip..\n"; #drop_app_user($orig_master_handler); &drop_vip(); ## Waiting for N * 100 milliseconds so that current connections can exit my $time_until_read_only = 15; $_tstart = [gettimeofday]; my @threads = get_threads_util( $orig_master_handler->{dbh}, $orig_master_handler->{connection_id} ); while ( $time_until_read_only > 0 && $#threads >= 0 ) { if ( $time_until_read_only % 5 == 0 ) { printf "%s Waiting all running %d threads are disconnected.. (max %d milliseconds)\n", current_time_us(), $#threads + 1, $time_until_read_only * 100; if ( $#threads < 5 ) { print Data::Dumper->new( [$_] )->Indent(0)->Terse(1)->Dump . "\n" foreach (@threads); } } sleep_until(); $_tstart = [gettimeofday]; $time_until_read_only--; @threads = get_threads_util( $orig_master_handler->{dbh}, $orig_master_handler->{connection_id} ); } ## Setting read_only=1 on the current master so that nobody(except SUPER) can write print current_time_us() . " Set read_only=1 on the orig master.. "; $orig_master_handler->enable_read_only(); if ( $orig_master_handler->is_read_only() ) { print "ok.\n"; } else { die "Failed!\n"; } ## Waiting for M * 100 milliseconds so that current update queries can complete my $time_until_kill_threads = 5; @threads = get_threads_util( $orig_master_handler->{dbh}, $orig_master_handler->{connection_id} ); while ( $time_until_kill_threads > 0 && $#threads >= 0 ) { if ( $time_until_kill_threads % 5 == 0 ) { printf "%s Waiting all running %d queries are disconnected.. (max %d milliseconds)\n", current_time_us(), $#threads + 1, $time_until_kill_threads * 100; if ( $#threads < 5 ) { print Data::Dumper->new( [$_] )->Indent(0)->Terse(1)->Dump . "\n" foreach (@threads); } } sleep_until(); $_tstart = [gettimeofday]; $time_until_kill_threads--; @threads = get_threads_util( $orig_master_handler->{dbh}, $orig_master_handler->{connection_id} ); } ## Terminating all threads print current_time_us() . " Killing all application threads..\n"; $orig_master_handler->kill_threads(@threads) if ( $#threads >= 0 ); print current_time_us() . " done.\n"; $orig_master_handler->enable_log_bin_local(); $orig_master_handler->disconnect();