keepalived+MySQL实现高可用

keepalived+MySQL实现高可用插图



(一)keepalived概述

Keepalived通过VRRP(虚拟路由冗余协议)协议实现虚拟IP漂移。当master故障后,VIP会自动漂移到backup,这时通知下端主机刷新ARP表,如果业务是通过VIP连接到服务器的,则此时依然能够连接到正常运行的主机,RedHat给出的VRRP工作原理如下图:

keepalived+MySQL实现高可用插图(1)

本来对VIP漂移有一定了解的我,看了上面的图后,越来越懵了。因此只能根据我的个人理解,来对keepalived的VIP漂移做一个解释了,假设我现在有一套这样的环境:
主机A的IP地址为:192.168.10.11
主机B的IP地址为:192.168.10.12

我们再单独定义一个keepalived使用的VIP:192.168.10.10

当2台主机安装了keepalive并正常运行时,keepalive会选择一个节点做为主节点(这里假设为主机A,IP为192.168.10.11),由于A是主节点,所以主机A上还会生成一个IP地址192.168.10.10,即虚拟IP(Virtual IP,也称VIP),此时我们使用192.168.10.10访问主机,访问到的主机是A;假如A主机上的keepalived由于某些原因(例如服务器宕机、用户主动关闭…)关闭了,keepalived备用节点会检查与主节点keepalived的通信是否正常,检测到不正常,则会提升一个备节点为主节点,相应的虚拟IP也会在对应的主机上生成,从而实现高可用的目的。

keepalived+MySQL实现高可用插图(2)

(二)MySQL是如何结合keepalived实现高可用的

在MySQL中,通过搭建MySQL双主复制,保持2台主机上的MySQL数据库一模一样,并在2台主机上安装keepalived软件,启用VIP,用户应用程序通过VIP访问数据库。当包含VIP的主机上的数据库发生故障时,关闭keepalived,从而将VIP漂移到另一个节点,用户依然可以正常访问数据库。 (这里需要注意,虽然MySQL架构双主复制,2个节点都可以写入数据,但是我们在使用的时候,是通过VIP访问其中一个实例,并没有2个数据库实例一起使用)。这里我简单画了一个流程图,来说明keepalive与MySQL实现高可用的过程:

keepalived+MySQL实现高可用插图(3)

(三)keepalived+MySQL实现高可用过程实现

基础环境规划:

主机名 IP地址 备注
服务器A hosta 192.168.10.11 keepalive主节点
服务器B hostb 192.168.10.12 keepalive备节点
192.168.10.10 虚拟IP,会在keepalive启动后分配到上面2台机器的主节点上

(3.1)搭建MySQL双主复制环境

STEP1:安装MySQL过程见:https://www.cnblogs.com/lijiaman/p/10743102.html

STEP2:配置双主复制参数

服务器A 服务器B

[mysqld]
basedir=/usr/local/mysql
datadir=/mysql/data

server_id = 1
binlog_format=ROW
log_bin=/mysql/binlog/master-bin
auto-increment-increment = 2            #字段变化增量值
auto-increment-offset = 1               #初始字段ID为1
slave-skip-errors = all                 #忽略所有复制产生的错误
gtid_mode=ON
enforce-gtid-consistency=ON

[mysqld]
basedir=/usr/local/mysql
datadir=/mysql/data

server_id = 2
binlog_format=ROW
log_bin=/mysql/binlog/master-bin
auto-increment-increment = 2            #字段变化增量值
auto-increment-offset = 2               #初始字段ID为2
slave-skip-errors = all                 #忽略所有复制产生的错误
gtid_mode=ON
enforce-gtid-consistency=ON

STEP3:创建复制用户,2个数据库上都要创建

grant replication slave on *.* to 'rep'@'%' identified by '123';

STEP4:将hosta的数据拷贝到hostb,并应用

[[email protected] ~]# mysqldump -uroot -p123456 -h 192.168.10.11 --single-transaction --all-databases --master-data=2  > hosta.sql
[[email protected] ~]# mysql -uroot -p123456 < hosta.sql

STEP5:hostb上开启复制,以下脚本在hostb上执行

-- 配置复制
mysql> CHANGE MASTER TO
     ->   master_host='192.168.10.11',
     ->   master_port=3306,
     ->   master_user='rep',
     ->   master_password='123',
     ->   MASTER_AUTO_POSITION = 1;
Query OK, 0 rows affected, 2 warnings (0.01 sec)

-- 开启复制
mysql> start slave;
 Query OK, 0 rows affected (0.00 sec)


-- 查看复制状态
mysql> show slave status G
 *************************** 1. row ***************************
                Slave_IO_State: Waiting for master to send event
                   Master_Host: 192.168.10.11
                   Master_User: rep
                   Master_Port: 3306
                 Connect_Retry: 60
               Master_Log_File: master-bin.000001
           Read_Master_Log_Pos: 322
                Relay_Log_File: hostb-relay-bin.000002
                 Relay_Log_Pos: 417
         Relay_Master_Log_File: master-bin.000001
              Slave_IO_Running: Yes

             Slave_SQL_Running: Yes

STEP6:hosta上开启复制,以下脚本在hosta上执行

mysql> CHANGE MASTER TO
    ->    master_host='192.168.10.12',
    ->    master_port=3306,
    ->    master_user='rep',
    ->    master_password='123',
    ->    MASTER_AUTO_POSITION = 1;
Query OK, 0 rows affected, 2 warnings (0.01 sec)

mysql> start slave;
Query OK, 0 rows affected (0.01 sec)

mysql> show slave status G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.10.12
                  Master_User: rep
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: master-bin.000001
          Read_Master_Log_Pos: 154
               Relay_Log_File: hosta-relay-bin.000002
                Relay_Log_Pos: 369
        Relay_Master_Log_File: master-bin.000001
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes

STEP7:测试双主复制

在hosta上创建数据库testdb,到hostb服务器上查看数据库是否已经创建

-- hosta上创建数据库
create database testdb;


--hostb上查看数据库,发现已经创建
mysql> show databases;
 +--------------------+
 | Database           |
 +--------------------+
 | information_schema |
 | db1                |
 | lijiamandb         |
 | mysql              |
 | performance_schema |
 | sbtest             |
 | sys                |
 | testdb             |
 +--------------------+
 8 rows in set (0.01 sec)

在hostb的testdb数据库上创建表t1,并插入数据,到hosta上查看是否复制过来

-- 在hostb上创建表并插入数据
mysql> use testdb
Database changed
mysql> create table t1(id int,name varchar(20));
Query OK, 0 rows affected (0.01 sec)

mysql> insert into t1 values(1,'a');
Query OK, 1 row affected (0.01 sec)


-- 在hosta上查看数据,数据已经过来
mysql> select * from testdb.t1;
+------+------+
| id   | name |
+------+------+
|    1 | a    |
+------+------+
1 row in set (0.00 sec)

到这,双主复制已经搭建完成,接下来安装配置keepalived。

(3.2)安装配置keepalived

(3.2.1)keepalived的安装与管理

keepalived可以使用源码安装,也可以使用yum在线安装,这里直接使用yum在线安装:

[[email protected] data]# yum install -y keepalived

使用如下命令查看安装路径:

[[email protected] data]# rpm -ql keepalived
/etc/keepalived
/etc/keepalived/keepalived.conf
/etc/sysconfig/keepalived
/usr/bin/genhash
/usr/lib/systemd/system/keepalived.service
/usr/libexec/keepalived
/usr/sbin/keepalived
/usr/share/doc/keepalived-1.3.5
… 略

使用如下命令管理keepalived

# 开启keepalived
systemctl start keepalived 或者 service keepalived start 

# 关闭keepalived
systemctl stop keepalived 或者 service keepalived stop 

# 查看keepalived运行状态
systemctl status keepalived 或者 service keepalived status

# 重新启动keepalived
systemctl restart keepalived 或者 service keepalived restart

(3.2.2)keepalived的配置

keepalived的配置文件为:/etc/keepalived/keepalived.conf,我的配置文件如下:

【hosta主机的配置文件】

[[email protected] keepalived]# cat keepalived.conf
! Configuration File for keepalived
       
global_defs {
notification_email {
[email protected]
[email protected]
}
       
notification_email_from [email protected]
smtp_server 127.0.0.1 
smtp_connect_timeout 30
router_id MASTER-HA
}
       
vrrp_script chk_mysql_port {       #检测mysql服务是否在运行。有很多方式,比如进程,用脚本检测等等
    script "/mysql/chk_mysql.sh"   #这里通过脚本监测
    interval 2                     #脚本执行间隔,每2s检测一次
    weight –5                      #脚本结果导致的优先级变更,检测失败(脚本返回非0)则优先级 -5
    fall 2                         #检测连续2次失败才算确定是真失败。会用weight减少优先级(1-255之间)
    rise 1                         #检测1次成功就算成功。但不修改优先级
}
       
vrrp_instance VI_1 {
    state BACKUP                  #这里所有节点都定义为BACKUP
    interface ens34               #指定虚拟ip的网卡接口
    mcast_src_ip 192.168.10.11    #本地IP 
    virtual_router_id 51          #路由器标识,MASTER和BACKUP必须是一致的
    priority 101                  #定义优先级,数字越大,优先级越高,在同一个vrrp_instance下,MASTER的优先级必须大于BACKUP的优先级。 
    advert_int 1
    nopreempt                     #不抢占模式,在优先级高的机器上设置即可,优先级低的机器可不设置         
    authentication {   
        auth_type PASS 
        auth_pass 1111     
    }
    virtual_ipaddress {    
        192.168.10.10             #虚拟IP 
    }
      
track_script {               
   chk_mysql_port             
}
}


【hostb主机的配置文件】

[[email protected] keepalived]# cat keepalived.conf
! Configuration File for keepalived
       
global_defs {
notification_email {
[email protected]
[email protected]
}
       
notification_email_from [email protected]
smtp_server 127.0.0.1 
smtp_connect_timeout 30
router_id MASTER-HA
}
       
vrrp_script chk_mysql_port {
    script "/mysql/chk_mysql.sh"
    interval 2            
    weight -5                 
    fall 2                 
    rise 1               
}
       
vrrp_instance VI_1 {
    state BACKUP
    interface ens34 
    mcast_src_ip 192.168.10.12
    virtual_router_id 51    
    priority 99          
    advert_int 1         
    authentication {   
        auth_type PASS 
        auth_pass 1111     
    }
    virtual_ipaddress {    
        192.168.10.10
    }
      
track_script {               
   chk_mysql_port             
}
}

需要特别注意:nopreempt这个参数只能用于state为BACKUP的情况,所以在配置的时候要把master和backup的state都设置成BACKUP,这样才会实现keepalived的非抢占模式!

在配置完成之后,启动MySQL数据库和keepalive,需要注意,先启动MySQL,再启动keepalive,因为keepalive启动后会检测MySQL的运行状态,如果MySQL运行异常,keepalive会自动关闭。

(3.3)高可用测试






时间轴

(时间递增)

hosta操作 hostb操作
时间1

# 数据库运行正常
[[email protected] ~]# service mysqld status
  SUCCESS! MySQL running (8530)


#keepalived运行正常
[[email protected] ~]# service keepalived status
    Active: active (running) since Mon 2020-08-03 22:29:10 CST; 1min 32s ago


# 此时虚拟IP在hosta上
[[email protected] ~]# ip addr
3: ens34: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
     link/ether 00:0c:29:fb:62:0a brd ff:ff:ff:ff:ff:ff
     inet 192.168.10.11/24 brd 192.168.10.255 scope global ens34
        valid_lft forever preferred_lft forever
     inet 192.168.10.10/32 scope global ens34
        valid_lft forever preferred_lft forever
     inet6 fe80::20c:29ff:fefb:620a/64 scope link
        valid_lft forever preferred_lft forever

# 数据库运行正常

[[email protected] ~]# service mysqld status
  SUCCESS! MySQL running (8022)
 

#keepalived运行正常

[[email protected] ~]# service keepalived status
    Active: active (running) since Mon 2020-08-03 22:31:09 CST; 8s ago


[[email protected] ~]# ip addr
3: ens34: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
     link/ether 00:0c:29:92:3d:5a brd ff:ff:ff:ff:ff:ff
     inet 192.168.10.12/24 brd 192.168.10.255 scope global ens34
        valid_lft forever preferred_lft forever
     inet6 fe80::20c:29ff:fe92:3d5a/64 scope link
        valid_lft forever preferred_lft forever

时间2

# 通过VIP访问数据库,访问到的都是hosta上的实例
[[email protected] keepalived]# mysql -uroot -p123456 -h192.168.10.10 -e “select @@hostname”
mysql: [Warning] Using a password on the command line interface can be insecure.
+————+
| @@hostname |
+————+
| hosta      |
+————+

# 通过VIP访问数据库,访问到的都是hosta上的实例
[[email protected] ~]# mysql -uroot -p123456 -h192.168.10.10 -e “select @@hostname”
  mysql: [Warning] Using a password on the command line interface can be insecure.
  +————+
  | @@hostname |
  +————+
  | hosta      |
  +————+

时间3

# 主节点关闭MySQL
[[email protected] keepalived]# service mysqld stop
Shutting down MySQL………… SUCCESS!

时间4

# keepalived检测到MySQL关闭后,会自动关闭
[[email protected] keepalived]# service keepalived status
    Active: inactive (dead)


# 此时VIP已经不存在
[[email protected] keepalived]# ip addr
3: ens34: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
     link/ether 00:0c:29:fb:62:0a brd ff:ff:ff:ff:ff:ff
     inet 192.168.10.11/24 brd 192.168.10.255 scope global ens34
        valid_lft forever preferred_lft forever
     inet6 fe80::20c:29ff:fefb:620a/64 scope link
        valid_lft forever preferred_lft forever

# hostb上的keepalived运行正常
[[email protected] ~]# service keepalived status
    Active: active (running) since Mon 2020-08-03 22:31:09 CST; 6min ago


# 发现VIP已经切换到了hostb
[[email protected] ~]#  ip addr
3: ens34: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
     link/ether 00:0c:29:92:3d:5a brd ff:ff:ff:ff:ff:ff
     inet 192.168.10.12/24 brd 192.168.10.255 scope global ens34
        valid_lft forever preferred_lft forever
     inet 192.168.10.10/32 scope global ens34
        valid_lft forever preferred_lft forever
     inet6 fe80::20c:29ff:fe92:3d5a/64 scope link
        valid_lft forever preferred_lft forever

时间5

# 通过VIP访问数据库,访问到的都是hosta上的实例
[[email protected] keepalived]# mysql -uroot -p123456 -h192.168.10.10 -e “select @@hostname”
mysql: [Warning] Using a password on the command line interface can be insecure.
+————+
| @@hostname |
+————+
| hostb      |
+————+

# 通过VIP访问数据库,访问到的都是hosta上的实例
[[email protected] ~]# mysql -uroot -p123456 -h192.168.10.10 -e “select @@hostname”
mysql: [Warning] Using a password on the command line interface can be insecure.
+————+
| @@hostname |
+————+
| hostb      |
+————+

时间6

# 重启MySQL
[[email protected] keepalived]# service mysqld start
Starting MySQL. SUCCESS!


# 重启keepalived
[[email protected] keepalived]# service keepalived start
Redirecting to /bin/systemctl start keepalived.service
[[email protected] keepalived]#
[[email protected] keepalived]# service keepalived status
Redirecting to /bin/systemctl status keepalived.service
    Active: active (running) since Mon 2020-08-03 22:40:08 CST; 6s ago


# 因为使用了非抢占模式,VIP不会漂回来
# 如果要把VIP漂回来,可以关闭hostb上的数据库或者直接关闭hostb服务器

[[email protected] keepalived]# ip addr
3: ens34: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
     link/ether 00:0c:29:fb:62:0a brd ff:ff:ff:ff:ff:ff
     inet 192.168.10.11/24 brd 192.168.10.255 scope global ens34
        valid_lft forever preferred_lft forever
     inet6 fe80::20c:29ff:fefb:620a/64 scope link
        valid_lft forever preferred_lft forever

【完】

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