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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

  1. 从宕机崩溃的Master保存二进制日志事件（binlog event）；
  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Slave；
  4. 应用从Master保存的二进制日志事件；
  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 {
      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=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

文章链接： https://www.mfisp.com/9824.html

文章标题：MySQL之高可用组件MHA

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