香港服务器的MySQL之高可用组件MHA
1 简介
MHA（Master High Availability）是由日本人yoshinorim开发的一款成熟且开源的MySQL高可用程序，它实现了MySQL主从环境下MASTER宕机后能够自动进行单次故障转移的功能，其本身由perl语言编写，安装方便，使用简单
MHA Master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 Manager主要运行一些工具，比如masterha_manager工具实现自动监控MySQL Master和实现master故障切换，其它工具实现手动实现master故障切换、在线master转移、连接检查等
MHA Node部署在所有运行MySQL的服务器上，无论是master还是slave。主要作用有三个
Ⅰ、保存二进制日志 如果能够访问故障master，会拷贝master的二进制日志
II、应用差异中继日志 从拥有最新数据的slave上生成差异中继日志，然后应用差异日志
III、清除中继日志 在不停止SQL线程的情况下删除中继日志
MHA工作原理
从宕机崩溃的Master保存二进制日志事件（binlog event）；
识别含有最新更新的Slave；
应用差异的中继日志（relay log）到其他Slave；
应用从Master保存的二进制日志事件；
提升一个Slave为新的Master；
使其他的Slave连接新的Master进行复制；
MHA数据补偿
当SSH能连接,从库对比主库GTID 或者position号,立即将二进制日志保存至各个从节点并且应用(save_binary_logs )
当SSH不能连接, 对比从库之间的relaylog的差异(apply_diff_relay_logs)
2 环境部署
节点 ip
主节点 10.243.95.3
从节点1 10.243.95.4
从节点2 10.243.95.5
数据库复制一主两从架构，MHA node部署在每个节点上，MHA manager部署在从节点2上
2.1 建立SSH互信
#各节点生成rsa密钥
ssh-keygen -t rsa
#发送密钥至三台服务器实现互信
ssh-copy-id root@10.243.95.3
ssh-copy-id root@10.243.95.4
ssh-copy-id root@10.243.95.5
2.2 搭建主从复制
具体内容见上篇主从复制，注意mha57以下版本不支持GTID事务，需避雷，按需选择下面的部署方法
2.3 安装依赖包
2.3.1 MHA-0.57-el6版本
#1.所有节点安装以下依赖包
yum -y install perl-DBD-MySQL perl-ExtUtils-MakeMaker perl-CPAN
yum install -y perl-DBD-MySQL perl-Config-Tiny perl-Log-Dispatch perl-Parallel-ForkManager perl-Time-HiRes
#2.所有节点安装mha-node包
rpm -ivh mha4mysql-node-0.57-0.el6.noarch.rpm
#3.管理节点安装mha-manage包
rpm -ivh mha4mysql-manager-0.57-0.el6.noarch.rpm
2.3.2 MHA-0.55-el6版本
#1.解压mha包
unzip -u mha_pack.zip
cd mha_pack/mha_pack/rhel6/mha2
#2.安装依赖
rpm -ivh perl-DBI-1.609-4.el6.x86_64.rpm
rpm -ivh perl-DBD-MySQL-4.013-3.el6.x86_64.rpm
rpm -ivh mha4mysql-node-0.54-0.el6.noarch.rpm
rpm -ivh perl-DBI-1.609-4.el6.x86_64.rpm
rpm -ivh perl-DBD-MySQL-4.013-3.el6.x86_64.rpm
rpm -ivh mha4mysql-node-0.54-0.el6.noarch.rpm
rpm -ivh perl-Config-Tiny-2.12-7.1.el6.noarch.rpm
rpm -ivh perl-TimeDate-1.16-11.1.el6.noarch.rpm
rpm -ivh perl-MailTools-2.04-4.el6.noarch.rpm
rpm -ivh perl-Email-Date-Format-1.002-5.el6.noarch.rpm
rpm -ivh perl-MIME-Types-1.28-2.el6.noarch.rpm
rpm -ivh perl-MIME-Lite-3.027-2.el6.noarch.rpm
rpm -ivh perl-Mail-Sender-0.8.16-3.el6.noarch.rpm
rpm -ivh perl-Mail-Sendmail-0.79-12.el6.noarch.rpm
rpm -ivh perl-Params-Validate-0.92-3.el6.x86_64.rpm
rpm -ivh perl-Log-Dispatch-2.27-1.el6.noarch.rpm
rpm -ivh perl-Parallel-ForkManager-0.7.9-1.el6.noarch.rpm
rpm -ivh perl-Time-HiRes-1.9721-127.el6.x86_64.rpm
rpm -ivh mha4mysql-manager-0.55-0.el6.noarch.rpm
2.4 配置文件
新建mha配置文件：vi /etc/masterha/app1.cnf
[server default]
# mysql root user and password
user=root
password=123456
# mysql log locations
#master_binlog_dir=/mysql/data
# user to use SSH around the cluster
ssh_user=root
# repl user and password
repl_user=repl
repl_password=123456
# working directory on the manager
manager_log=/root/mha/log/manager.log
manager_workdir=/root/mha/log
#remote_workdir=/mysql/mha/log
# MHA ping interval
ping_interval=5
## scripts to support MHA functions
## secondary_check_script= /usr/bin/masterha_secondary_check -s remote_host1 -s remote_host2
master_ip_failover_script= /root/mha/scripts/master_ip_failover
## shutdown_script= /usr/local/masterha/scripts/power_manager
## report_script= /usr/local/masterha/scripts/send_report
master_ip_online_change_script= /root/mha/scripts/master_ip_online_change
# masters
[server1]
hostname=10.243.95.3
port=3306
candidate_master=1
master_binlog_dir=/opt/mysql/binlog
remote_workdir=/root/mha/log
[server2]
hostname=10.243.95.4
port=3306
candidate_master=1
check_repl_delay=0
master_binlog_dir=/opt/mysql/binlog
remote_workdir=/root/mha/log
[server3]
hostname=10.243.95.5
port=3306
candidate_master=1
check_repl_delay=0
master_binlog_dir=/opt/mysql/binlog
remote_workdir=/root/mha/log
2.5 切换脚本
1）创建一些目录
#建立mha的文件夹
mkdir -p /root/mha/conf
mkdir -p /root/mha/log
mkdir -p /root/mha/scripts
chmod -R 777 /root/mha/scripts
2）新建脚本
在线切换脚本
vi /root/mha/scripts/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;
my (
$command, $ssh_user, $orig_master_host, $orig_master_ip,
$orig_master_port, $orig_master_user, $orig_master_password,
$new_master_host, $new_master_ip, $new_master_port,
$new_master_user, $new_master_password
);
my $vip = ‘192.168.90.30’; # writer Virtual IP
my $gw = `route|grep default|awk ‘{print \$2}’`;
chomp($gw);
my $interface = ‘eth0’; # network interface
my $ssh_start_vip = “ip addr add $vip/32 dev $interface”;
my $ssh_ping = “arping -U -I $interface -s $vip $gw -c 5”;
my $ssh_stop_vip = “ip addr del $vip/32 dev $interface”;
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,
‘orig_master_user=s’ => \$orig_master_user,
‘orig_master_password=s’ => \$orig_master_password,
‘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,
);
$ssh_user = ‘root’ unless ($ssh_user);
exit &main();
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. Set read_only= 1 on the current master
# 3. Kill current queries
# 4. Deegister original master’s ip to the catalog database
# * 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();
## 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();
## Deregister original master’s VIP
print “Disabling the VIP on old master: $orig_master_host \n”;
&stop_vip();
$exit_code = 10;
## After finishing the script, MHA executes FLUSH TABLES WITH READ LOCK
$exit_code = 0;
};
if ($@) {
warn “Got Error: $@\n”;
exit $exit_code;
}
exit $exit_code;
}
elsif ( $command eq “start” ) {
# 1. Register new master’s ip to the catalog database
# We don’t return error even though activating updatable accounts/ip failed so that we don’t interrupt slaves’ recovery.
# If exit code is 0 or 10, MHA does not abort
my $exit_code = 10;
eval {
## Update master ip on the catalog database, etc
print “Enabling the VIP – $vip on the new master – $new_master_host \n”;
&start_vip();
$exit_code = 0;
};
if ($@) {
warn “Got Error: $@\n”;
exit $exit_code;
}
exit $exit_code;
}
elsif ( $command eq “status” ) {
# do nothing
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 \”`;
`ssh $ssh_user\@$new_master_host \” $ssh_ping \”`;
}
# 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 {
“Usage: master_ip_online_change –command=start|stop|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”;
die;
}
注：若提示用户无repl权限且确认已添加，检查mysql.user表下的repl用户是否存在其它host存在repl权限为N的行，因为mha检查到任意行存在N即返回失败
2.6.3 故障自动切换验证
1、开启三个数据库节点实例，确保主从复制状态正常(执行2.6.2操作)
2、后台打开监控程序，并持续监控日志
4、完成切换
MySQL之高可用组件MHA
故障切换内容：
检查到master不通，尝试继续ping检查，达到阈值5触发自动切换
若配置文件未指定候选节点，根据日志量选举新的master主节点
若主节点未宕机，移除原master节点的vip
其他节点与新的master建立复制关系，主从复制同步中
新master节点启动vip，完成切换
2.6.4 手动切换
1）主节点已宕机
2）主节点未宕机