MySQL的高可用(MHA)

MHA简介

MHA:Master High Availability,对主节点进行监控，可实现自动故障转移至其他从节点；通过提升某一从节点为新的主节点，基于主从复制实现，还需要客户端配合实现，目前MHA主要支持一主二从，即一台充当master，一台充当备用master，另外一台充当从数据库，出于机器成本的考虑，淘宝进行了改造，目前淘宝TMHA已经一主一从。

MHA架构

MHA的工作原理

MHA是由一台manager服务器远程监控主服务器,当主服务器挂了提升一台从服务器作为主服务器。
当主节点挂了，manager首先要查看哪台从节点，同步的数据最多，然后提升同步最多的从节点为主节点，再将其余的MySQL服务器对他做从节点。
如果原主节点没彻底死透，manager会让新的主机通过ssh协议远程连接到原先的主节点，拉取二进制日志进行同步。如果主节死透了那就放弃。　　

MHA搭建

环境准备

一、准备4台主机，管理节点1台，主节点MySQL服务器1台，从节点MySQL服务器2台

二、将Manager管理节点配置为时间服务器，向所有MySQL服务器提供时间同步。

1.安装chrony服务

<code class="language-bash">[root@Manager ~]# yum install -y chrony</code>

2.修改chrony配置文件

<code class="language-bash">[root@Manager ~]# vim /etc/chrony.conf 
server 172.22.0.1 iburst
allow 192.168.0.0/16
local stratum 10</code>

3.启动chrony服务

<code class="language-bash">[root@Manager ~]# systemctl start chronyd</code>

4.将MySQL服务器与Manager服务器进行时间同步
4.1在所有MySQL主机上修改配置文件并启动，并启动服务

<code class="language-bash">[root@Master ~]# sed -i ‘/^server 0/i server 192.168.73.111 iburst‘ /etc/chrony.conf
[root@Master ~]# systemctl start chronyd</code>

4.2确认时间同步

<code class="language-bash">[root@Master ~]# chronyc sources -v
210 Number of sources = 1
  .-- Source mode  ‘^‘ = server, ‘=‘ = peer, ‘#‘ = local clock.
 / .- Source state ‘*‘ = current synced, ‘+‘ = combined , ‘-‘ = not combined,
| /   ‘?‘ = unreachable, ‘x‘ = time may be in error, ‘~‘ = time too variable.
||                                                 .- xxxx [ yyyy ] +/- zzzz
||      Reachability register (octal) -.           |  xxxx = adjusted offset,
||      Log2(Polling interval) --.      |          |  yyyy = measured offset,
||                                \     |          |  zzzz = estimated error.
||                                 |    |           MS Name/IP address         Stratum Poll Reach LastRx Last sample               
===============================================================================
^* 192.168.73.111                4   6   377    54    +25us[  +41us] +/-  105ms</code>

三、配置ssh为的密钥认证登陆

当主节点宕机，manager会让从节点通过ssh协议去尝试连接主节点，并拉取二进制日志，所以要时用密钥的认证方式让从节点登陆到主节点拉取数据。
1.在manager服务器上生成私钥文件

<code class="language-bash">[root@Manager ~]# ssh-keygen 
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:yAvC2PJUlRyAf1udlrVXzmIsUljTdUdW6X6FVpQ3Ajo root@Manager
The key‘s randomart image is:
+---[RSA 2048]----+
|   ..ooo   ++. +%|
|  .  .o   o oo.=*|
|   ..    E = oo*o|
| + ...... B o B.+|
|o = ..ooS. . =...|
| + . ...       ..|
|  .   .         .|
|                 |
|                 |
+----[SHA256]-----+</code>

2.将公钥文件复制给自己

<code class="language-bash">[root@Manager ~]# ssh-copy-id 127.0.0.1</code>

3.将整个~/.ssh目录复制给所有的MySQL主机

<code class="language-bash">[root@Manager ~]# scp -r ~/.ssh 192.168.73.110:/root</code>

至此所有环境准备完毕

一、配置主从复制

主节点配置

1.修改配置文件

<code class="language-bash">[root@Master ~]# vim /etc/my.cnf
[mysqld]
server-id=1
log-bin
binlog-format=row
skip_name_resolve</code>

2.启动数据库服务

<code class="language-bash">[root@Master ~]# systemctl start mariadb</code>

3.创建主从复制账号

<code class="language-bash">[root@Master ~]# mysql -e "GRANT REPLICATION SLAVE ON *.* TO ‘repluser‘@‘192.168.73.%‘ IDENTIFIED BY ‘centos‘;"</code>

4.添加mha的管理账号，让管理节点远程连接到主机用来设置主从调整

<code class="language-bash">[root@Master ~]# mysql -e "GRANT ALL ON *.* TO ‘mhauser‘@‘192.168.73.%‘ IDENTIFIED BY ‘centos‘;"</code>

从节点配置

1.修改配置文件

<code class="language-bash">[root@Slave1 ~]# vim /etc/my.cnf
[mysqld]
server-id=2
read-only
log-bin
relay_log_purge=0
skip_name_resolve</code>

2.启动服务

<code class="language-bash">[root@Slave1 ~]# systemctl start mariadb</code>

3.配置CHANGE MASTER TO

<code class="language-bash">MariaDB [(none)]> CHANGE MASTER TO MASTER_HOST=‘192.168.73.110‘, MASTER_USER=‘repluser‘,MASTER_PASSWORD=‘centos‘,MASTER_PORT=3306,MASTER_LOG_FILE=‘mariadb-bin.000001‘,MASTER_LOG_POS=245;
Query OK, 0 rows affected (0.00 sec)</code>

4.启动线程

<code class="language-bash">MariaDB [(none)]> START SLAVE;
Query OK, 0 rows affected (0.00 sec)</code>

在Slave2节点上也执行相同的操作，此处步骤省略，需要注意server-id需要修改为和其他主从节点不同

5.测试
主节点导入hellodb库

<code class="language-bash">[root@Master ~]# mysql < hellodb_innodb.sql</code>

从节点查看是否同步
slave1

<code class="language-bash">[root@Slave1 ~]# mysql -e "SHOW DATABASES;"
+--------------------+
| Database           |
+--------------------+
| information_schema |
| hellodb            |
| mysql              |
| performance_schema |
| test               |
+--------------------+</code>

Slave2

<code class="language-bash">[root@Slave2 ~]# mysql -e "SHOW DATABASES;"
+--------------------+
| Database           |
+--------------------+
| information_schema |
| hellodb            |
| mysql              |
| performance_schema |
| test               |
+--------------------+</code>

二、配置管理节点及被管理节点

1.在管理节上安装mha4mysql-manager、mha4mysql-node，将两个包放在同一目录下

<code class="language-bash">[root@Manager ~]# yum install *.rpm -y  #这两个包有依赖管理需要一起安装</code>

2.在所有被管理节点上安装mha4mysql-node

<code class="language-bash">[root@Master ~]# yum install mha4mysql-node-0.56-0.el6.noarch.rpm -y</code>

<code class="language-bash">[root@Slave1 ~]# yum install mha4mysql-node-0.56-0.el6.noarch.rpm -y</code>

<code class="language-bash">[root@Slave2 ~]# yum install mha4mysql-node-0.56-0.el6.noarch.rpm -y</code>

3.在管理节点上创建配置文件

<code class="language-bash">[root@Manager ~]# vim /etc/mha/aap1.conf
[server default] 
user=mhauser 
password=centos
manager_workdir=/data/mastermha/app1/ 
manager_log=/data/mastermha/app1/manager.log 
remote_workdir=/data/mastermha/app1/ 
ssh_user=root 
repl_user=repluser 
repl_password=centos
ping_interval=1
[server1] 
hostname=192.168.73.110
candidate_master=1 
[server2] 
hostname=192.168.73.112
candidate_master=1 
[server3]
hostname=192.168.73.113
candidate_master=1 </code>

4.做检查
4.1检查ssh连接

<code class="language-bash">[root@Manager ~]# masterha_check_ssh --conf=/etc/mha/aap1.conf </code>

4.2检查主从复制

<code class="language-bash">[root@Manager ~]# masterha_check_repl --conf=/etc/mha/aap1.conf </code>

5.以上两项全部成功后启动程序
mha这个程序是跑在前台的，一次性的可以使用nohub或screen来解决跑在前台的问题

<code class="language-bash">[root@Manager ~]# masterha_manager --conf=/etc/mha/aap1.conf </code>

三、测试

1.在master上跑个存储过程，导入存储过程

<code class="language-bash">[root@Master ~]# mysql hellodb < testlog.sql </code>

2.调用存储过程

<code class="language-bash">MariaDB [(none)]> USE hellodb
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
MariaDB [hellodb]> call pro_testlog;</code>

3.另起一个主节点窗口将主节点断网

<code class="language-bash">[root@Master ~]# ifdown ens33</code>

4.manager端完成切换退出，查看日志，查看新的主节点是哪台slave

<code class="language-bash">[root@Manager app1]# tail /data/mastermha/app1/manager.log
Started automated(non-interactive) failover.
The latest slave 192.168.73.112(192.168.73.112:3306) has all relay logs for recovery.
Selected 192.168.73.112(192.168.73.112:3306) as a new master.
192.168.73.112(192.168.73.112:3306): OK: Applying all logs succeeded.
192.168.73.113(192.168.73.113:3306): This host has the latest relay log events.
Generating relay diff files from the latest slave succeeded.
192.168.73.113(192.168.73.113:3306): OK: Applying all logs succeeded. Slave started, replicating from 192.168.73.112(192.168.73.112:3306)
192.168.73.112(192.168.73.112:3306): Resetting slave info succeeded.
Master failover to 192.168.73.112(192.168.73.112:3306) completed successfully.
#此处显示最新的主节点为192.168.73.112</code>

由于从节点在配置文件中定义的为read-only，此时被提升为主能执行写操作时应为管理服务器上有管理账号，他将从节点的服务器全局变量read_only给关闭了

<code class="language-bash">[root@Slave1 ~]# mysql -e "SELECT @@read_only;"
+-------------+
| @@read_only |
+-------------+
|           0 |
+-------------+</code>

为了防止服务服务重启再次变为read-only，此时需要对新主节点的配置文件进行修改将read-only行注释

<code class="language-bash">[mysqld]
server-id=2
#read-only
log-bin
relay_log_purge=0
skip_name_resolve</code>

四、测试新的主节点

1.对hellodb.teachers表插入数据

<code class="language-bash">[root@Slave1 ~]# mysql -e "INSERT hellodb.teachers VALUES(5,‘Tang San‘,30,‘M‘);"</code>

2.Slave2主机上查看是否同步

<code class="language-bash">[root@Slave2 ~]# mysql -e "SELECT * FROM hellodb.teachers;"
+-----+---------------+-----+--------+
| TID | Name          | Age | Gender |
+-----+---------------+-----+--------+
|   1 | Song Jiang    |  45 | M      |
|   2 | Zhang Sanfeng |  94 | M      |
|   3 | Miejue Shitai |  77 | F      |
|   4 | Lin Chaoying  |  93 | F      |
|   5 | Tang San      |  30 | M      |    #已经同步
+-----+---------------+-----+--------+</code>

其他事项

当原主节点被修复后，将其添加为从节点使用。

MySQL的高可用(MHA)

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