MHA集羣

MHA Manager（管理節點）

——可以單獨部署在一臺獨立的機器上，管理其他節點

——也可以試部署在一臺slave節點上

MHA Node(數據節點)

——運行在每臺MySQL服務器上

MHA工作過程

由Manager定時探測集羣中的master節點

當master故障時，master自動將擁有最新數據的slave提升爲新的master

關鍵點

從宕機崩潰的master保存二進制日誌事件
識別含有最新更新的slave
應用差異的中繼日誌（relay log）到其他的slave
應用從master保存的二進制日誌事件
提升一個slave爲新的master
使其他的slave連接新的master進行復制

拓撲圖：

一、配置所有數據節點主機之間可以互相以ssh密鑰對方式認證登陸

二、配置manager56主機無密碼ssh登錄所有數據節點主機

三、配置主從同步,要求如下：

51 主庫開半同步複製
52 從庫（備用主庫）開半同步複製
53 從庫（備用主庫）開半同步複製
54 從庫不做備用主庫所以不用開半同步複製
55 從庫不做備用主庫所以不用開半同步複製

不讓從庫把中繼日誌刪掉，默認會刪掉

mysql> set global relay_log_purge=off;
Query OK, 0 rows affected (0.13 sec)

配置數據庫服務器：(51~55)
           yum -y install perl-DBD-mysql // 安裝依賴包
           rpm -ivh mha4mysql-node-0.56-0.el6.noarch.rpm
配置管理服務器:(56)
           yum -y install perl-DBD-mysql // 安裝依賴包
           rpm -ivh mha4mysql-node-0.56-0.el6.noarch.rpm //先裝Noed在安裝Manager
           yum -y install perl-ExtUtils-* perl-CPAN-*
           tar -zxvf mha4mysql-manager-0.56.tar.gz //源碼安裝Manager
           cd mha4mysql-manager-0.56/
perl Makefile.PL
           make
           make install

[root@mha ~]# mkdir /etc/mha_manager/

[root@mha ~]# cp /opt/mha4mysql-manager-0.56/samples/conf/app1.cnf /etc/mha_manager/

[root@mha ~]# cp /opt/mha4mysql-manager-0.56/samples/conf/master_ip_failover /etc/mha_manager/

[root@mha ~]# vim /etc/mha_manager/app1.cnf //修改MHA配置文件

[server default]
manager_workdir=/etc/mha_manager //定義軟件路徑
manager_log=/etc/mha_manager/manager.log //指定log日誌位置
master_ip_failover_script=/etc/mha_manager/master_ip_failover //自動failover的切換腳本

ssh_user=root //ssh用戶名
ssh_port=22
repl_user=replication //主從同步用戶名
repl_password=123qqq...A // 主從密碼
user=root // 數據庫用戶名
password=123qqq...A // 數據庫密碼

[server1] //添加管理主機
hostname=192.168.4.50
candidate_master=1 //設置爲候選master

[server2]
hostname=192.168.4.51
candidate_master=1

[server3]
hostname=192.168.4.52
candidate_master=1

[server4]
hostname=192.168.4.53
no_master=1 //不競選master

[server5]
hostname=192.168.4.54
no_master=1

添加授權用戶： //用於MHA檢測集羣狀態

mysql> grant all on *.* to root@"%" identified by "123qqq...A";
Query OK, 0 rows affected (0.10 sec)

添加授權用戶： //用於主從授權

grant replication slave on *.* to replication@"%" identified by "123qqq...A";
Query OK, 0 rows affected (0.12 sec)

測試：

SSH測試：

[root@mha ~]# masterha_check_ssh --conf=/etc/mha_manager/app1.cnf

主從配置測試：

[root@mha ~]# masterha_check_repl --conf=/etc/mha_manager/app1.cnf

編輯VIP轉換腳本： vim /etc/mha_manager/master_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錛�
#  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;

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
);

my $vip = '192.168.4.100/24';  # Virtual IP 
my $key = "1"; 
my $ssh_start_vip = "/sbin/ifconfig eth0:$key $vip";
my $ssh_stop_vip = "/sbin/ifconfig eth0:$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,
  'new_master_user=s'     => \$new_master_user,
  'new_master_password=s' => \$new_master_password,
);

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
      &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 {
      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";
      $new_master_handler->enable_log_bin_local();
      $new_master_handler->disconnect();

      ## Update master ip on the catalog database, etc
      &start_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 start_vip() {
    `ssh $ssh_user\@$new_master_host \" $ssh_start_vip \"`;
}
sub stop_vip() {
    return 0 unless ($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";
}

啓動MHA：

[root@mha ~] # masterha_manager --conf=/etc/mha_manager/app1.cnf --remove_dead_master_conf --ignore_last_failover

--remove_dead_master_conf //當主庫壞掉，會自動將這個數據庫踢出集羣，在配置文件app1.cnf中將主庫的配置刪除，當你修復好之後需要在配置文件app1.cnf中添加回去

--ignore_last_failover // 默認一臺壞掉另外一臺頂上去，在8個小時之內又壞了，就不會再切換主機了，所以需要把這個關掉

[root@mha ~] # masterha_check_status --conf=/etc/mha_manager/app1.cnf //查看服務器狀態

停止master50，主庫會動態遷移

將被刪除的50添加到集羣

mysql>change master to master_host="192.168.4.51",master_user="replication",master_password="123qqq...A",master_log_file="master51.000003",master_log_pos=154; // 將50設置爲現在的主庫51的從庫

mysql> start slave;
mysql> show slave status\G;

在56中將刪除的50信息添加回去
       ]# vim /etc/mha_manager/app1.cnf
               [server1]
               candidate_master=1
               hostname=192.168.4.50

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