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 [email protected]
ssh-copy-id [email protected]
ssh-copy-id [email protected]

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 {
    print
  “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=portn”;
    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

  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